The Saltwater Vertical Story

The Saltwater Vertical Experiment has three phases:

Phase I. Inductively-loaded 1/4 wl vertical.

Phase II: Full-size 1/4 wl vertical. 

Phase III: Phase two 1/4 wl verticals.

PHASE I: Inductively-loaded Portable Vertical

Inductively-loaded 21' Portable Vertical with 2-Elevated Radials

Construction Details • The inductively-loaded 1/4WL vertical is constructed out of a half-element from a Tennadyne T-6 log periodic, measuring 21' in length. The base is 1"OD and tapers to .375". It rides beautifully in high winds; there is no need for guys. Set-up requires 8 minutes, with dismantling being done in 3 minutes. Anyone deploying saltwater verticals in DXpeditions might consider using a tapered element. It retracts inside itself; shipping length = 6'.`

Top Hat Made from Hustler Stingers

Capacity Hat: The 21' vertical is crowned by a capacity hat (made from the 3 extra stingers Hustler provides with its MO-4 "short" mobile mast). Measuring 26" each, the stingers are inserted through holes drilled through the end of a short aluminum tube which slips over the (.375") top section. #18 AWG solid (hook-up) wire completes the circuit, lending the top-hat its hexagonal shape. The design exhibits low windloading. The aerial's resonance can be pruned by sliding the top section up and down the top element. 

Design Note: No consideration was given to how much the top-hat would lower the resonant frequency of the 21' vertical. The philosophy was to load it as much as possible with a lossless top hat before bringing it to resonance with a lossy loading coil. A superlative demonstration of the small vertical on receive is provided below.

Test Sites

The inductively-loaded vertical is operated at seaside locations along the southern coast of Rhode Island. 

First Test Site • Point Judith, Rhode Island

The flag seen in the map above identifies Point Judith, R.I., which juts out into the Atlantic Ocean, affording a clear, over-the-water shot to the East, South and south of West. The Northeast path to Europe is also over saltwater across the (Narragansett) bay opening at the southern end of the state. This provides 2 to 5 miles of unobstructed salt water before encountering Newport, R.I.  Listening to JAs longpath from this location with only a mobile Hustler whip testifies to the great reception at this site, as heard in the video below.

A blow up of the area around Point Judith is provided in the map below. The red flag appearing off-shore identifes the second test site, Deep Hole, at Matunuck, R.I. The site is about 4 miles to the west of Point Judith. Both locations exhibit low-noise radio reception with even the most modest of antennas.

Second Test Site • Matunuck Point, Rhode Island

Deep Hole at Matunuck Point allows public access to the ocean--just over the dune seen in the photo above. 50' coaxial lines are all that is needed to connect the inductive-loaded 21' vertical to the mobile rig in the car. The aerial is affixed to 4x4's supporting the dune fence. The best signal report thus far received from JAs longpath on 40 Meters is 59+5dB. With a shelf extending 300' offshore, Matunuck Point facilitates the siting of vertical antennas directly over salt water. 

Shelf Extending Out 300' • Excellent Location for Verticals Sited Over Saltwater • Deep Hole • Matunuck, R.I.

At high tide, the water swamps the shelf to a depth of no more than 3 feet, enabling one to access the verticals with waders (if necessary). Extending 800' parallel to the shoreline, and 300' to the breaking waves, the shelf allows sufficient space to experiment with phased arrays. Smaller waves successively breaking into shore, as seen in the photographs above, indicate the shallow depth of the water over the shelf. If the surfer in the photo stood up, the water would be at his knees.

Second Test Site • Deep Hole • Matunuck Point, R.I.

Swamped twice daily by the ocean, the shoreline at Matunuck Point is nonetheless protected from the pounding surf--except during tidal surges accompanying coastal storms. The site faces due south. The photograph below details the earliest installation of the inductively-loaded 21' vertical, and its attendant, resonant radials, for the purpose of tuning the aerial. An example of the type of propagation possible from locations such as this can be heard in the video below.

Tuning Jig • Matunuck Point, Rhode Island

At Matunuck Point, PVC caps affixed to 4x4 posts along a dune fence accept PVC stubs which serve as stand-off insulators for the two elevated radials. By pulling the PVC stand-offs out of the PVC end-caps, the elevated verticals are removed from the site. On a few occasions in the winter, the stand-offs and elevated radials remained at the test site between operations--reducing installation of the portable vertical to inserting the aluminum element into the PVC insulating tube, tightening a connecting screw and attaching the coaxial feedline. Done. 

The Portable Base Support

Depicted at the Pont Judith location below, the portable vertical base support is made form a 1" PVC tube, and affixed to the 4x4 post by two metal brackets ($2.45/dozen @ Home Depot). A 1/2" plexiglass sheet was inserted between the metal brackets and the 4x4 post to lift the Z-match coil off the post. Both were subsequently replaced with a metal bracket used to hang electrical conduit, affording the clearance needed by the Z-match coil while eliminating the need for a screw gun to install the vertical. This replacement bracket is discussed shortly.

Portable Vertical Insulating Base Support • Two Versions

The brackets used to support PVC insulating base were changed to allow the base to be spaced off the wooden post.

***

Below the lower mounting bracket, a shunt coil is wound around the PVC tube. Channels cut into the PVC tube enable the value of the Z-match coil to be varied (1 uh to 2.3 uh) to tweak the feedpoint SWR at varying saltwater sites. Below the shunt inductor is the SO-239 connector, the ground connection for radials and a 1:1 current balun to isolate the feedline. Connection between the top of the Z-match coil and the aluminum element is made by a metal tab cut froom aluminum flashing. All wiring connections are made inside the PVC tube. The system works perfectly.

Initial Effort Results in Utter Failure

The earliest attempts to work JAs longpath using a portable vertical from Point Judith failed miserably, despite assistance provided by Canadian amateurs. In the installation photographed above, several errors compounded to doom the effort despite its location adjacent to the Atlantic Ocean. Amongst the errors are (i) use of non-resonant radials (ii) laid on the ground; (iii) driving a ground rod adjacent to the base feedpoint of the vertical, and then (iv) attaching the radials and shield of the coax to this ground rod. Additional errors include (v) making no attempt to use a shunt inductor across the feedpoint to match the vertical to the 50 ohm coaxial feedline. 

In the video below, you can hear how poorly the vertical seen in the photographs above performed. Without assistance from Canadian and Japanese hams, it is likely no contacts would have been made.

THE EVOLUTION OF THE LOADING COIL

A 3" diameter air-wound coil is inserted across an insulated spacer in the vertical. The coil is then compressed, stretched and otherwise mangled until the vertical resonates at the target frequency of 7.130 Mhz. The coil is removed and measured (with an MFJ analyzer) to determine how much inductance is needed to resonate the vertical. The magic number is 5.4 uh.

Pliable Loading Coil Used During Initial Tuning

The coil is then mounted coaxially within the vertical to see if it detunes the aerial. It does not. The center insulator is replaced with a beefier section of PVC tubing due to high winds encountered at Point Judith. 

A section of fiberglass rod arrives from MaxGain Systems (5/8" @ 4' = $7). It replaces the PVC tube as the center insulator in the vertical element. This strengthens the vertical sufficiently to withstand sustained winds encountered at Matunuck Point. The loading coil can continue to be stretched and squeezed to resonate the vertical. 

Third Iteration of Loading Coil

After resonating the vertical, the coil is removed and measured with the MFJ antenna analyzer (5.4 uh). I now know 5.4 uh is needed to resonate the vertical using two elevated radials. I re-wind the coil in a more efficient form, so that it will obtain a higher Q and work more efficiently in the vertical. Closer-spacing not only results in the use of less wire, but brings the coil's physical dimensions more closely to the coveted 1:1.5 form factor. So, two strips of plexiglass are clamped on top of one another, and a series of holes are drilled through both. After separation, the two pieces are trimmed with a Dremel tool and threaded onto the loading coil. Done.

Fourth Iteration of Loading Coil

But now the coil is too big. The MFJ analyzer measures it at 7.4uh. I find the 5.4uh spot on the coil, and snip the excess wire off--removing about 1.5 feet. What this shows is that less wire can be used for the same amount of inductance, this reducing the coil losses, by winding the coil in a uniform fashion. The compact, robust loading coil is then re-mounted into the vertical. Attention is paid to leave space between the ends of the coil and the aluminum tubing on each end so as to furtehr reduce losses. When the aerial is set up at Point Judith, it works perfectly. Done.

Fourth Iteration of Loading Coil

But now the coil is too big. The MFJ analyzer measures it at 7.4uh. I find the 5.4uh spot on the coil, and snip the excess wire off--removing about 1.5 feet. What this shows is that less wire can be used for the same amount of inductance, this reducing the coil losses, by winding the coil in a uniform fashion. The compact, robust loading coil is then re-mounted into the vertical. Attention is paid to leave space between the ends of the coil and the aluminum tubing on each end so as to furtehr reduce losses. When the aerial is set up at Point Judith, it works perfectly. Done.

Conclusion

We can tell from the photo that not much inductance is needed to resonate the portable vertical. This is due to (i) the aerial's significant length compared to a full-sized vertical, (ii) its use of a capacity hat, and (iii) the placement of the loading coil near the bottom. How these factors affect the vertical's performance is worthy of review.

Since the current distribution along a 1/4 wave vertical goes from its maximum at the base to its minimum at the top, combined with the fact that the aerial radiates in proportion with this current distribution, it turns out that more energy radiates from the lower part of the vertical. So when we shorten a vertical by inductively loading it we want to place the loading coil up as high as possible because, as far as radiation is concerned, the lower part of the vertical is its filet mignon. Above the loading coil the current and radiation will always taper off (per unit length). From the photograph above we can now see that we placed the loading coil fairly low in our portable vertical--only about 1/3rd the way up. This sequesters maximum efficiency to a mere 1/3rd of its reduced length. Although this was done to strengthen the vertical in high winds, it does not represent optimal placement of the loading coil, electromagnetically. 

Buttressed by this new knowledge you might posit, "Let's put the loading coil up higher to get more of the filet mignon at the bottom". This makes sense, and will increase your signal reports. But there are trade-offs which limit this strategy, one of which being the higher you place the coil, the larger the coil must be. Let's see how this and additional see-sawing factors eventually balance out to optimum coil placement.

Left out of our discussion until now is the important fact that the voltage distribution along a 1/4 wave vertical is inversely-proportional to it current distribution. This means that the voltage is minimum at the base of the vertical, and maximum at its top. Imagine a full-sized 1/4-wave vertical with the voltage lowest at the bottom and highest at the top. And then imagine cutting out a section and substituting in a coil. In the shortened vertical you just created the voltage will still be lowest at its bottom and highest at its top. But the gradual rise in this voltage will not occur at the point where you installed a coil. At this spot the voltage abruptly increases--as if to make up for the missing section--and appears as a voltage across the coil. 

Let's try to understand this another way using a physical scenario. Suppose you want to take a 35-foot, 1/4-wavelength vertical on 40 meters and reduce it to 12 feet by adding a loading coil. And that you've decided to put the loading coil way up in the vertical--like 2 feet from the top--to grab as much of the filet mignon below as possible. That means the first 10 feet of the vertical (below the loading coil) radiates as well as the first ten feet of the full-sized vertical. Bravo! You've cut a nice piece of filet mignon out of that 12 foot vertical. But when you install the loading coil at the ten-foot mark, a large voltage will develop across it because there's only two more feet of vertical above it. Since the voltage maximum sits at the top of the vertical, two feet below--at the top of the loading coil--there is a lot of voltage! And since the bottom of your loading coil connected at the vertical's ten-foot mark--where there's a lot less voltage--a large voltage develops across the loading coil. This is how RF voltage across the loading coil gets bigger the higher up you place it in the vertical. The "omega point" for the coil is reached when it starts arcing between windings, or exhibits coronal discharge off protrusions. 

If you've made it this far in this explanation, you learned a good amount about inductively-loaded verticals. You might now be able to apply this understanding to the verticals abounding around you. For example, Hustler high-power mobile whips may use bigger loading coils not only to dissipate more heat, but to also deal with higher RF voltages across them. Hamstick mobile antennas get around this problem by spreading out the windings of their loading coils over most of the antenna, enabling them to be used at high power levels. So don't expect to see Hamstick marketing any QRO versions. And if you're really good, you'll be able to project this knowledge out to the operation of loaded horizontal antennas, possibly understanding why hams have migrated away from multiband "trap" yagis . Or why Chuck, K1KW--when ordering a pair of 2-element, 40 meter yagis from JK Antennas--asked them to move the loading coils a little bit further out on the elements. Chuck likes filet mignon!

PHASE II: Full-size 1/4 WL Vertical

Full-sized 1/4 Wavelength Vertical: Tuned at Home QTH

Phase II of the Saltwater Experiment centers on the construction of a full-sized, 1/4 wavelength portable vertical. This larger size raised concerns about whether a single person could manhandle it during installation at windy coastal locations. I opted to tune the full-sized vertical at home. The early prototype was mounted on the back deck of the house, where its mechanical behavior in high winds was conveniently recorded in the photographs below.

The Mathematical Error

I miscalculate the length of a 1/4 wavelength vertical by dividing 468 by the frequency, and then taking 1/2 of the results. This is wrong because the formula 468/f provides the half-wavelength (in feet) of a wire dipole over ground, taking into account end-effects. My (mis)use of the formula produces results which are too short. The more accurate formula is 246/f  -- which is derived from 492/f -- the half-wavelength of a dipole in free-space. This, in turn, is derived the from the classic physics formula 300/f, which provides the length (in meters) of one-wavelength in free-space. Even after writing this part of the story, hams contact me and insist that 234/f is the correct formula to determine the length of a 1/4-wave vertical. And that the same formula is also the correct one to calculate 1/4 wavelength spacing in a phased array. This is, of course, incorrect. Inter-element spacing, for example, must be calculated in free space. 

Anyhow, since my fundamental error occurs upstream, disasterous consequences result downstream. Both the vertical and radial lengths were too short. And when Phase III was initiated, the two phased verticals were spaced too close to one another: 32.5 feet, instead of the 34.5 feet of free-space feet required for 7.150 Mhz operation. As detailed shortly, I had to set a third 4x4 post a mere three feet from the first to correct the inter-element spacing error. Both 4x4's, about three feet apart, remain to this day as monuments to my error. 

The upcoming photographs beautifully document this error. The reader will note such things as multiple holes drilled in aluminum tubing, the lengthening of elevated radials and the setting of the third 4x4 post perhaps as evidencing the experimentalist's adherence to instrument readings. I say this because I was not aware of the mathematical error, but it did show up in the MFJ antenna analyzer's readins. Thus, when physical dimensions do not agree with mathematical (mis)calculations, the true experimentalist will adjust physical parameters in accordance with his instrument's readings. In my case, it never occurred to me that I had made a theoretical error. My nose was buried in my measuring instrument. This prevented me from realizing the mathematical error had occurred upstream. Luckily, my father, a retired physics professor, monitors this entire process. After noticing my complaints about everything being "too short", he asked me what formula I was using to make the calculations. When I told him, he looked back at The New York Times he was reading while remarking that the dividing the speed of light by the frequency would give me the length of the vertical, if I divided the result by four. Done. 

Having been set on the right course, I was able to (re)calculate the length of a 1/4 wavelength vertical resonating at 7.150 Mhz, as provided below. It is constructed of 6' sections of aluminum tubing, available from DX Engineering for about $30.

1/4 Wavelength Element Tapering  (34' 4" / 7.150 Mhz)

6' Sections	Joint Overlap	Exposed Section Length
Section 1	0	6
Section 2	2'	4
Section 3	6"	5'4"
Section 3.5	1' 3.75"/5.5"	2'
Section 4	5.5"	5' 6.5"
Section 5	3"	5' 9"
Section 6	3"	5' 9"

NOTE: Section 3.5 was added while lengthening the vertical to compensate for the aforementioned mathematical error. It consists of a splice comprised of a 2' length of tubing of the same diameter as Section 3 through which a 3' section of tubing (with the same diameter as Section 4) is inserted. This enables the 2' splice (Section 3.5) to be inserted between Sections 3 & 4, effectively extending Section 3. The resulting joint overlaps are 1' 3.75" and 5.5". 

Improved Mounting Bracket

The original metal brackets used for the 21' loaded vertical were replaced by another type which eased installation of the full-sized 1/4 WL vertical at portable locations. The new type of brackets are used to hang electrical conduit, and eliminate use of a screw gun during installation. The vertical base support tube snaps into the bracket at the most vulnerable stage of (single-handed) installation. The brackets also provide the spacing needed between the z-match coil located at the bottom of the base insulator and the 4x4 post, as seen in previous photographs detailing the 21' loaded vertical.

Improved Bracket Eliminates Need for Screw Gun • Removing PVC Tube Sections Reduces Dielectric Losses

Reduction of dielectric losses is achieved by removing sections of PVC tubing not needed for mechanical support. This method may not work at portable locations where the wooden base post is too short to support the aluminum element above it top. In such cases it would be better to use one section of PVC tube which extends above the top of the wooden base post. Shortening the PVC insulating tubes exposes the aluminum base element, thus raising the possibility of feeding the vertical through a gamma-type match--although the 50-ohm match-point likely occurs above the aluminum exposed between base insulators. Any such gamma-type matching scheme requires installing a conductor parallel to the vertical element up to the 50-ohm match-point. As shortly noted, a gamma-type match is facilitated by mechanical means used to feed the vertical.

Mechanical Feedpoint Connection 

For reasons having nothing to do with electrical design, I decided that the electromagnetic energy should be equally applied to both sides of the aluminum tubes. I did this because whenever I look at devices wired by RF engineers, I see physical symetery rivaling fine art sculptures. Gentle arcs in wires; right angles blunted. Twin feedlines drape symeterically down to a switching box suspended below and between the dual parasitic-driven elements by its own caternary line.

Symetery of RF Systems • 2-element Reversible Moxon • W1ZY • New York • 2005

Such aesthetic qualities are an aspect of how RF systems work well. Along such lines, a stainless steel machine screw passes through the PVC insulator and the base of the aluminum vertical element. The hole through the PVC tube is enlarged to the diameter of aluminum spacers which sandwich eith side of the vertical element, and then squeeze it when the stainless steel screw is tightened. This makes an electromagnetic connection at both sides of the aluminum element. 

Feedpoint Connection Made on Both Sides of the Vertical Element

It also causes the machine screw to protrude from both sides the PVC tube, affording connection points for the center wire of the coaxial feed on one side, and a RF choke to ground on the other (to bleed off static build-up). The stainless steel machine screw also prevents the aluminum element from slipping through the bottom of the PVC tube. Removing it allows the vertical element to be slipped in and out of the base insulators at seaside locations without having to remove them from the wooden support post. Even this step can be accomplished by snapping them from the metal brackets that hold them to the wooden support. To feed the vertical using a gamma-match, threaded rod could replace the stainless steel screw, in which case the length of the threaded rod constitutes the spacing between the gamma-match arm and the vertical element.

Initial Testing with 2 Elevated Radials

The Saltwater Vertical Experiment strives to use the same elevated radials with each vertical prototype. This allows the same base/radial system to be used with different types of verticals. To tune the full-size vertical, the radials used with the 21' loaded vertical (Phase I) are connected to its base. 

Tuning the 1/4 Wavelength Vertical • Common Mode Choke 

Resonating the 21' loaded vertical centered on adjusting its loading coil while keeping an eye on readings in the MFJ antenna analyzer. There were no calculations predicting physical dimensions governing its construction. It was assembled using available scraps, beginning with its top-hat--which was made as large as possible--followed by the vertical element assembled from sections of a T-6 in storage. The only variable was the loading coil, which was stretched/compressed until resonance was obtained. In the case of the 1/4 wavelength vertical, there is no top-hat or loading coil. The only variable to bring the system to resonance is the length of the vertical element. An easy proposition until one recalls that I miscalculated its resonant length--a problem compounded by my failure to realize this fact. Thus, when the vertical resonated at 7.650 Mhz, I assumed the radials needed to be lengthened.

Lengthening Radials to Compensate for Miscalculating Vertical Length

Naturally, it turned out the radials needed to be lengthened by the same amount lacking in the vertical in order to resonante the aerial on 7.150 Mhz (SWR: 1.5; X=40). When excited with 100 watts, DX stations were worked with common-mode intereference perplexing a television audio system. After adding an "ugly balun" to the feedline (wrapped around a mason jar), and ferrite bead chokes on the audio equipment, the common-mode interference was reduced, but the "locking" quality of the SWR and resonance curves remained. Being too windy to test the quarterwave vertical at any seaside location, I opted to build the second 1/4 wavelength vertical in order to phase them. A "test range" was established in the woods, partially to eliminate the common-mode problem related to mounting the full-sized vertical to the house. 

PHASE III: PHASED VERTICALS

Phasing Two Full-sized 1/4 Wavelength Verticals

For several days I tramp through the woods with a compass and a roll of mason line taking measurements collated on paper. Back in the workshop, I draw up a crude map highlighting openings in the canopy, and skew its polar coordinates to reflect the true-north readings not provided by the compass. This allows me to determine possible azimuth orientations for the phased verticals. The best I can do is site the verticals slightly north of East--covering Europe, Africa and South America--and slightly south of due West, covering the Pacific, Australia and New Zealand.

It should be noted that a phased vertical array is not a high-gain antenna. Adding a second vertical and phasing it with the first only doubles your signal strength. Maybe a little bit more, if you are meticulous with the tuning. Aside from their low take-off angle, and the dispersal of your 3 to 4 dB increase in signal strength over 120 degrees, the main advantage of phased verticals is their rejection of rearward signals--nominally 25 to 30 dB. So, if situated on the East coast of the United States, orienting a pair of phased verticals to the east reduces stateside QRM coming from the west. As later discovered, and as shortly documented, this reduction of stateside QRM depends upon propagation. For in the late-afternoon, as the band opens up to Europe, stateside signals to the west begin to go down when the array is flipped to the east. By 8 o'clock or so, when the propagation begins to go long, the reduction of American signals increases. And as night fully envelopes, the 40 meter phone band can appear devoid of stateside signals. In fact, the first time I scan across the band after installing the second vertical--and before I added the remote switching relay--I think something is wrong with the antenna because the few American signals I can hear are so weak. Below S-9. I go outside with a flashlight to rearrange the cables to reverse the array's directivity. When I return to the workshop, the same scan across the same frequencies produces a bevy of powerful stateside signals. Dayem. It's alive!

But these events are yet to unfold. They are weeks away from the cold, early-March afternoon when, as snow flakes begin to fall, I find myself in the woods pushing a wheel-barrow along what would become the well-trampled path to the West vertical. It ferries a 50 lb bag of concrete, a five-gallon bucket of water and a post-hole digger. After the hole is dispatched and some gravel thrown in, an eight-foot 4x4 is tipped until one end thunks down deep in the hole. The cement follows, evenly distributed around the post. The level of a carpenter's square assures the post is upright. For the next fifteen-minutes, water trickles from the bucket and is allowed to seep into the Quickrete cement. About an hour later the cement is set. The 2x4 serving as a base for the vertical is attached to the 4x4 post with 3" sheetrock screws later replaced with 8" carriage bolts. The entire episode takes less than two hours. Done. 

After setting the first post, the two counterpoise wires used in Phase I are strung under the 1/4 wavelength vertical to provide a counterpoise for initial tuning. Which does not go well. The vertical resonates on 7.6 Mhz, and shows a feedpoint impedance of 45 ohms with a healthy reactive component. This is not good, and manifests the fact that the formula I am using, 234/f, is wrong. Although I don't know that yet. I tune the vertical by lengthening the counterpoise wires, which works; the vertical now resonates in the 40 meter phone segment, but with the reactive component and high feedpoint impedance. Back in the workshop, the other end of the feedline shows an impedance of around 90 ohms. I could use the transmatch to tune this out if it was not for the fact that the transmatch is already being used to match the exciter and the amplifier. To top it off, my (mis)calculation calls for the vertical to be a lot shorter than it actually needs to be, and, thus, I never ordered enough aluminum from DX Engineering to make it the correct length. I stop the vertical experiment altogether in order to resolve these problems. Besides, the snow flurries outside transformed into a blizzard. And who wants to work outside in that?

Inside, I shift focus to reconditioning the Heathkit SB-221 amplifier--something on my bucketlist for the past 35 years. To achieve a 1:1 SWR between it and the exciter liberates the tuner to match the amplifier to the antenna feedline. This, in turn, allows testing of the vertical which may lead to figuring out what's wrong with it. At least so I think. So, while reading and re-reading elevated-radial technical papers at night, by day I strip down the Heathkit SB-221 to its bare chassis, removing all components and wiring assemblies. I throw them into a cardboard box for later sorting. I am not scared. 

Upright recycle bins provided by the local town government serve as operating tables, enabling me to walk around the amplifier while working on its revitalization.

For the next 6 days I listen to podcasts of NPR's "Car Talk", with "Click and Clack, the Tappet Brothers" troubleshooting mechanical problems as I do the same. I wet-sand the chassis before reassembling the amplifier--which goes easily since it is a kit. 

Final improvements include: re-capping the HV power supply; adding the Harback rectifier/metering and soft-key boards; grounding the grids; removing the "CB filter"; re-tuning the input circuits; removal of Rich Measures parasitic chokes; new "french" parasitic chokes; rewound the filament transformer; new ceramic capacitors; removal of black paint from RF deck; DeToxit cleaning of potentiometers, bandswitch & relay contacts; cleaning and rewinding the tank coil; rewiring of input & output bandswitch wafers; new SO-239 connectors; installation of AC transient spike suppressors; new grommets; new coaxial lines; new circuit breakers; disabling of 120 VDC cathode cut-off bias; rebuilding of 120 VDC power supply; oiling cooling fan; acoustic silencing of cooling fan mount; removal and cleaning of tube sockets; cleaning of tube socket connectors; cleaning of tube pins; re-painting rear air intake grill; etc. Done. 

The Completed SB-221 Restoration

Constructing Phased Verticals

Impractical Considerations

Installing a vertical element is effortless compared to the construction of its elevated-radial system, which takes weeks. There is no way to speed up this job, and you will be consigned to commuting to the site many more times than you anticipate. Assembling tools in a small bag removes one more thing "to do" when heading out to the work site. This may run contrary to those who subscribe to the view that four elevated-radials are sufficient for reasonably efficient operation of the vertical. This view was retracted in 2012 by its main progenitor, Rudy Severns, N6LF, in a lengthy, technical paper reporting the results of meticulous field studies of elevated radial systems (http://rudys.typepad.com/files/qex-mar-apr-2012.pdf ). As things turn out, 20 to 25 elevated radials stabilizes the behavior of the vertical; it begins to behave in accordance with textbook theory. This eases the meticulous tuning required when two verticals are pressed into a phased vertical system. This is partly due to the symeteric distribution of displacement currents between the higher number of elevated-radials, thus reducing the problem of asymetric currents inherent in 4-elevated radial systems. The larger number of elevated radials also more effectively screens the vertical from the ground, thus reducing the need for a "chicken-wire" or buried radials to reduce ground losses--as recommended for the 4-elevated-radials scheme. The take away is that you will spend a significant amount of time in the field constructing the elevated radial system if you wish to end up with an efficiently-operating phased vertical array. From my experience, the assembly of a toolkit is both the first step and last chance to procrastinate. 

Tool Kit for Building Elevated Counterpoise Systems

I used a canvas tool bag available from Harbor Freightfor $6. I loaded the following tools and materials into it.

• diagonal cutters
• needle-nose pliers
• regular pliers
• adjustable wrench
• box cutter
• straight-phillips combo screwdriver
• screw-gun
• electrical tape
• Liquid Tape
• a roll of mason line
• a spool of ground wire
• a length of mason line equal to the length of an elevated-radial coiled around a PVC tube

Everything should remain in the tool bag at the end of the day. This increases productivity in the field by eliminating the need to put the tools away at night, only to re-assemble them at the start of the next work session.

Because I built the phased verticals in a wooded grove, I use a wheel barrow to ferry tools, a step ladder and cement bags out to the site--much in the same way that a contractor uses a work truck to do the same thing. Upon arrival, the wheel barrow serves as a means of laying out tools for easy access, and as a depository for wire and twine remnants properly disposed of later back at the workshop. This keeps the woods clear of debris of possible harm to wildlife--especially tangled webs of fishingline. 

Wheelbarrow Ferries Tools & Materials to Work Site

The general axiom is to approach construction of your phased vertical array in the same way that a carpenter approaches the construction of a house. Devise some means of organizing and transporting the tools, and of removing debris at the end of the day to keep the site clean. Why? Because installing a phased vertical array can get complicated. Its counterpoise system demands precision. You will find that the threading of pre-measured lengths of wires through shrubbery and undergrowth in a wooded area will be frequently delayed by unforseen snags. At times it may appear that every, single possibility for a line to get snagged is actualized. Many fractions of dBs can be lost when such frustrations are encountered during construction.

Zen and the Art of Phased Arrays

The reader might ask why I have focussed on the assembly of a toolkit, or how it eases the daily trek out to the antenna site. Although these things are self-evident, I include them in this narrative to buttress the state of mind needed to tackle this project. Sure, you can bang it out in an afternoon in time to show it off on the local, 40-meter cloud-burner's net. Or throw it together for yet another eHam article. But there is another approach. An approach we shall term the "Zen" of constructing the array. 

Verticals are finicky. The bands are strewn with carcasses of "verticals that don't work". This feeds the adage that verticals "radiate poorly in all directions." Yet, once in a while, one will encounter a vertical standing proud and tall holding court with DX stations in the late-afternoon sun. Or phased verticals disappearing into the noise when their directivity is flipped by old timers. One way to achieve such performance levels is to adopt an attitude in keeping with the array's finicky nature. A good mental starting point is to imagine yourself alone, before driving in the first post-hole, pausing to visualize your upcoming accomplishment. And that getting from here to there will take at least a couple weeks. At that point the phased verticals you are about to build already exist in your mind's eye. And all you have to do to get there is begin their physical construction by measuring each elevated radial wire precisely before stringing them symeterically from the base of each vertical, and then finishing off this part of the job by making sure they are all equally taught. And what to do where the elevated radials intersect? Each night, after finishing up in the field, you sit in your workshop fashioning insulated spacers from PVC tubes, replete with end-slits cut at the same complimentary angles as exhibited by each pair of intersecting wires. To make sure you got it right, you return to the field with a flashlight and a step ladder to pre-fit the insulators slated for installation the next day. Well, maybe you don't have to go that far. But you get the idea. When in the field working, you leave your body and watch yourself from above incrementally transfer into reality the antenna you've been imagining for months.

Attitudes like these minimize construction errors. For with every wire you splice, every solder connection you make, exists the potential for diminished performance. Fractions of a dB are lost when you implement a fudge-factor, or take a short-cut you know you shouldn't take. Since the difference between theoretical and actual performance is you, the disparity is under your control. Your attitude during construction is reflected in how well your aerial ends up working.

One's mental attitude plays a role in human endeavors beyond building antennas. It is found manifest, for example, in athletics. How often a golfer sinks a putt, a wide-receiver catches the pass, or how quickly the runner crosses the finish line are all affected by mental attitude. Mental attitude is a core element of all championship performances. The same holds true with building antennas. For before construction begins, you are the golfer before teeing-off, the receiver before hut-hut is heard, the bent runner readied for the starting gun. Envisage the idealized antenna at every step of building it. Go the extra mile when implementing solutions. Take a break when frustrated--even if you just took a break. Smokers--light up if you got 'em, for you are free to chain-smoke. This is the way of the antenna-builder. A mindset not known to those who purchase commercial antenna systems. 

Dealing with the Counterpoise System

Run Catenary Lines Around the Verticals

This phased vertical array employs two elevated-counterpoise systems electrically-isolated from one another. Each consists of thirty (30) 1/4-wavelength wires--for a total of sixty (60). They are strung out from the bases of the verticals in symeterical patterns. The far ends have insulators, and are tied off onto catenary lines run around the perimeters of both verticals. Eyehooks, sheetrock screws and other non-invasive fasteners are used to anchor the catenary lines to trees. When tensioned, the catenary systems are able to suspend the elevated radials about 12 feet above the ground. It is necessary to run the catenary lines in order to evenly distribute the radials from the bases of the verticals. No way around this. The catenary lines took a week to run around the verticals in the woods, at a time when the foilage (and insects) had yet to arrive. 

Short sections of PVC tube serve as end insulators. To keep the two elevated-counterpoise systems electrically insulated from one another, 6" PVC tubes serves as stand-off insulators wherever two counterpoise wires from opposing systems intersect one another.

End-insulators Made of 1/2" PVC Tubing

Catenary Lines Assure Symeteric Distribution of Elevated Counterpoise Wires • Radial Intersecting Points Electrically-Insulated and Spaced 6"

Catenary Lines Anchored to Trees • Non-invasive Fasteners • Wrapping Lines Around Tree Kills the Tree by Removing Ring of Bark

Construction techniques such as these harp back to the original wireless pioneers, who used readily-available materials--combined with their imaginations--to build their antenna systems. All of this has changed with the commoditization of ham radio equipment.

A lot has been written about the relationship between elevated counterpoise systems and vertical elements in phased arrays. The general axiom is that four (4) tuned, elevated radials will work as efficiently as 32 buried radials. This is not what I found in Phase III of the Saltwater Vertical Experiment. 

Near & Far Fields

Two concepts reveal how verticals work. The first is the "near field" of the antenna, and the second is the "far field" of the antenna. Reduced to the crudest of explanations, the near field of a vertical is a concept that links how well the antenna works with its immediate physical surroundings--e.g. how many watts it ends up radiating. The "near field" concept is understood to extend no more than several wavelengths from the vertical. And as you might have guessed, the vertical's radials--be they buried or elevated--greatly influence the vertical's "near field" behavior. This fact causes our attention to be focussed on the question of what exactly do these radials--be they buried or elevated--do? What is their purpose? 

This concern gives rise to the simple question: "How does the energy applied to the vertical element by the center of the coax get back to the shield of the coax?" 

The answer is that it completes the circuit by flowing through the portion of the earth contained within the near field of the vertical. 

In simplistic terms, you can visualize the transmitter putting power into the center conductor of the coax in the shack, and then this power goes along the center conductor to the vertical in the field. Once it hits the vertical element, it needs some kind of path back to the shield to complete its circuit. In a ground-mounted vertical, this "return" path is provided by the earth, itself.  Since soil conductivity is low, the displacement currents making their way back to the shield of the coax via the ground do so as if passing through resistors. You can think of it as a resistor placed in series with a 12 volt lamp, causing the lamp to dim. The more resistance encountered by the displacement currents, the less power is radiated by the vertical. The wasted power ends up heating the earth in the immediate vicinity of the vertical. To reduce such losses we need to reduce the resistance of the path taken by the displacement currents. And this is accomplished by burying as many radials as possible around the base of the vertical in an attempt to "short out" the "strings of resistors" represented by the ground conductivity in our model. The more wires you bury, the more strings of resistors you short out. None of this has anything to do with how well the vertical performs as a DX antenna--in terms of its predominant angle of radiation. That aspect is developed in the "far field" which we have yet to discuss.

In review: The near field has to do with the immediate vicinity of the antenna, and determines how much power ends up getting radiated. It encompasses several wavelengths out from the vertical. We try to increase the antenna's efficiency by burying radials into the earth to provide paths other than the lossy earth for the vertical's return currents. 

There's another way of offering a path for the return currents in a vertical, aside from a buried radial system. And this is through the use of "elevated radials", or more correctly "elevated counterpoise wires". When we use elevated counterpoise wires, we are lifting the feedpoint of the vertical up and away from the lossy ground. The displacement currents begin to flow more through the elevated radials than the lossy earth. Thus, the higher we elevate the counterpoise wires, the more we decouple the vertical from the earth. This reduces ground losses and thus increases the vertical's efficiency. To ultimately decouple the return currents from the lossy earth, we string out as many "elevated radials" as possible from the base of the vertical. Using only two or four elevated radials requires that they resonate on the same frequency as the vertical to encourage symeterical current distribution amongst them. As the number of elevated radials increases, the whole counterpoise system begins to loose resonance, thus alleviating the need to cut each radial wire to the exact length. Return currents are also more evenly distributed, which reduces the amount of current carried by any single wire.

When using small numbers of counterpoise wires, the elevated vertical's efficiency can be increased by burying radials or laying out chicken wire beneath the elevated radials to shield them from the lossy earth. Use of a large number of elevated counterpoise wires--above 30--renders such measures to no advantage because the larger system effectively shields the antenna from the lossy earth. 

So there you have it: a few paragraphs explaining the "near field" of a vertical antenna which will make any electrical engineer or physicist cringe. Is this actually how it works? No. But it serves as a starting point to dispell misinformation about the relation between vertical antennas and soil conductivity. Many think that if you have "good ground conductivity" you want to couple the vertical to the ground. Or that a vertical "wants" to "work against the ground". The fact of the matter is that in all instances except that of saltwater, one wants decouple the vertical from the earth as much as possible. Thus, if you ground-mount your vertical, you need to lay out or bury as many radials as possible to offset the resistance of the lossy earth. If you raise the vertical above the ground, you want to string out as many "elevated radials" as possible. And if you can string outonly a small number of "elevated radials," you can improve your vertical's efficiency by doing so over a buried radial system, or by laying out chicken wire beneath the antenna to further shield it from the ground. Further notions of adding salt or "watering" the ground beneath a vertical to enhance its efficiency, or substituting a radial system with a series of ground rods should now be dispelled. As well as the notion that vertical antennas will "play well" when installed over high water tables or on the shores of fresh water lakes. None of these are true. The difference between excellent and poor ground conductivity is measured in fractions of a dB. In both cases, and those inbetween, enhanced performance can be realized by taking measures to decouple the vertical from the earth. The take away is that the "ground" or "earth" is not a friend of the vertical, as far as the near field is concerned. The only near-field friend the vertical has is salt water.

Salt Water: A Unique Situation

Why is salt water so coveted amongst vertical enthusiasts? Why does locating a vertical on or near salt water enhance its performance? Taking all we have learned about the "near field" thus far, the answer is partially revealed by the table below.

Table 1

Soil Conductivities

We can use scientific notation to express the soil conductivities in Table 1.

VERY POOR - (1xe-3)

POOR -  (2e-3)

POOR - (2e-3)

GOOD/AVERAGE - (5e-3)

VERY GOOD - (3e-2)

SALT WATER - (500e-2 or 5000e-3)

The soil conductivites can now be expressed as integers raised to 10-3.

VERY POOR - 1

POOR -  2

POOR - 2

GOOD/AVERAGE - 5

VERY GOOD - 30

SALT WATER - 5000

At RF frequencies, salt water conducts:

• 5,000 times better than the worst soil;
• 2,500 times better than poor soil;
• 1,000 times better than average soil;
• and about 166 times better than the best soil.

It conducts better than soil by 2 to 3 orders of magnitude. What does this mean?

Orders of Magnitude

What is an order of magnitude? An order of magnitude simply means "ten times more". So, for example, if we increase our transmitter power from 1 watt to 10 watts, we have increased it by a factor of ten, which is an order of magnitude. And if we increase it again--this time going from 10 watts to 100 watts--we have increased our power by yet another order of magnitude. Doing the same thing again--this time going from 100 watts to 1,000 watts--means we end up running 3 orders of magnitude more power than the original 1 watt. On the receiving end, each order of magnitude increase in our transmitter power registers a 10 dB increase in our signal strength. So, if we increase our transmitter power by 3 orders of magnitude, our signal report will increase by 30 dB.

Such comparisons serve to provide a ballpark idea of how much better salt water conducts at RF frequencies than any type of soil. For most soils ("very poor" - "good/average"), salt water conducts about 30dB better. And for the best possible soil possible ("very good"), salt water conducts about 20 dB better. Does this mean that a vertical installed at the ocean will be 30 dB louder than when it is ground mounted inland? No--although these numbers do correlate with my own field experiments. What it does mean is that it is impossible to make up the 2 to 3 orders of magnitude difference between the conductivity of salt water and soil by adding salt to the ground beneath a vertical, or by watering it. Nor does installing a vertical aside a freshwater lake, or in an area with a high water table, improve the vertical's near field ground conductivity. What the numbers do show is that something special happens when salt water is found beneath a vertical. 

With regard to the near field, what this means is that the salt water vertical does not need as extensive a ground radial or elevated counterpoise system as an inland vertical does to achieve the same efficiency. When a vertical is situated near or over salt water, there is no need for scores of ground radials to "short out" the "series of resistors" representing poor soil conductivity at inland locations. You can get away with as few as 2 elevated radials. Why? Because in the case of the salt water vertical, it is not mounted over "lossy earth". It is mounted over a beautifully conductive plane that enhances the flow of (displacement) currents. No need to "bury" ground radials to increase its conductivity, or string out 30+ "elevated radials" to shield the vertical from it. 

And what about inland hams using vertical antennas and phased arrays? What does this mean to them? Their takeaway is to focus on their ground systems. For it is within the near field of inland vertical installations that extensive ground systems close the gap between the high-conductivity of salt water and the low-conductivity of soil. At a coastal installation, the high conductivity of salt water means that a less-extensive ground system is needed to achieve a high degree of efficiency compared to an inland installation, where the poorer soil conductivity necessitates a more extensive ground system. An inland vertical can operate as efficiently as a salt water vertical. It just takes a lot more wire.

Momentarily removing the salt water scenario from further consideration, and restricting our discussion to inland vertical installations, many technical papers point to the same conclusion; namely, that there is a point after which adding radials (whether buried or elevated) to a vertical does not increase its near field efficiency. There is a numerical limit. In the case of buried radials, the limit lies somewhere between 64 and 120 radials. If you add more radials above this range, the efficiency of the vertical does not increase--irrespective of soil type! The limit to the number of radials dovetails perfectly with the observation that the soil conductivities provided in Table 1 span a range resolving to a factor of about 50. This range is so miniscule compared to the orders of magnitude difference between the conductivity of salt water and all soil types that it undercuts the notion that a vertical's efficiency is limited by the soil conductivity of its location. A vertical in the desert, for example--with its "very poor" soil conductivity--can achieve the same efficiency as the vertical installed over "very good" ground because the difference between their soil conductivities is not technically insurmountable. Radials can be added to the vertical in the desert until it exhibits the same near field efficiency as the vertical over "very good" ground--which naturally uses fewer radials. Although both verticals will eventually reach the point where adding more radials doesn't enhance their efficiencies, the vertical over "very good" ground will require fewer radials than the vertical over "very poor" ground before this point is reached. 

Conclusion: Near Field

The near field has to do with the array's interaction with its immediate environment, which boils down to how efficiently it radiates. Most near field parameters can be controlled by the builder. In the case of our phased vertical array, the near field parameters include:

• system radiation efficiency;
• system resonant frequency;
• inter-element coupling & phase angle;
• feedpoint impedance & reactance at resonance
• 2:1 SWR bandwidth;
• vertical to elevated radial length ratio;
• feedline isolation.

The second concept we promised to cover is the Far Field.

Far Field

The far field has to do with how the local terrain, extending out hundreds of wavelengths from the antenna, shapes the antenna's radiation pattern. Obviously, the far field of a 40 meter antenna canot be controlled by its builder--aside from relocating the antenna. Which is why the Saltwater Vertical Experiment is so interesting: we move the vertical to different locations, which is tantamount to altering its far field. We can place it various distances from the shore. Or install it right on the shelf that extends 300' away from the shore--at Matunuck Point--and see if anything happens in the far field when the moon floods the near field with salt water. With the soil conductivities listed in Table 1, this would be an interesting experiment. 

But what is the Far Field? The far field is the terrain extending about 3 to 5 miles from the base of a 40 meter vertical. It is over this "far field" that the antenna's final directive pattern is sculpted--including how far above the horizon a vertical's low-angle lobe will hover. You can see what we are talking about in the radiation pattern graphs produced by antenna modelling programs, such as NEC.

If you look at modeling plots for a vertical, you see the vertical, which sits at the center of the graph, with two lobes coming out nearly perpendicular to it. If you look closely, you will notice the lower edges of these lobes do not hug the X-axis of the graph. The bottomside of the lobes execute a gentle, upward curve as they move out along the X-axis--sort of like the bow of a motorboat speeding through water. The bottom edge of the low-angle lobes is of highest concern to DXers. The lower this part of the curve gets to the X-axis, the lower the vertical's "take-off" angle. Making this "take-off" angle as low as possible is the Holy Grail sought by antenna designers, and the Ark of the Covenant used by SuperStations when pinning thousands of S-meters during contests. How does this work?

Let's suppose the "take-off" angle is zero (0), and thus the low-angle lobe is parallel to the horizon. In such circumstances, the radio wave propagates off the antenna and travels towards the horizon skimming the surface of the earth. By the time the radio wave propagates about 12 miles out, the curvature of the earth begins to cause its surface to drop away from the radio wave. As the wave continues outwards, the surface of the earth continues to drop away. Eventually, the radio wave is hundreds of miles above the surface of the earth. At this point, the radio wave would continue out into space if it was not for the ionisphere, which reflects most of it back towards earth. After doing so, the radio wave continues to travel, but on a collision course with the earth because the ionisphere has bent its trajectory back towards the ground. At a point about equal to the distance the radio wave has thus far traveled, it arrives at the surface of the earth. This is the point where the radio wave completes its first "hop", whereupon part of it bounces off the earth and heads skywards----on its way to another rendezvous with the ionisphere. The maximum single-hop distance for the F2 layer is about 4000 Km, and 2000 Km for the E layer.

The distance the radio wave travels before making its first terrestrial "bounce" is called the "skip zone"or "skip distance". For the purposes of DXing, we want this "skip zone" to be as long as possible because every time the radio wave "bounces" off the ionisphere or the earth, it gets weaker. Conventional wisdom estimates the attenuation at about 10 dB per hop. This means that your signal report from a DX station loses ~10 dB with every "hop" it makes on its way to the DX location. As the reader may have already deduced, lower take-off angles require fewer hops than higher take-off angles to get to the same DX location.

Review

Let's re-rack and go through this explanation again--this time assuming the predominant "take-off" angle is not parallel to the horizon, but 20 degrees above it. Under such circumstances, the predominant lobe radiates energy at 20 degrees above the horizon. Within the near and far fields, a smaller component will radiate at negative angles--meaning at angles below the horizon. Within the vertical's far field, these negative angle components will be reflected by the local terrain and eventually re-join the predominant 20-degree component--which has not been reflected by anything. The point at which the two angular components recombine sculpts the vertical's low-angle component. When the two angular components merge constructively, the vertical's low-angle component is enhanced. When the two angular components merge deconstructively, the vertical's low-angle component is not enhanced. The degree to which the two angular components end up recombining is determined by the extent to which the radio wave's polarization and phase are shifted when reflected by the local terrain. Should there be no shift, the two components recombine constructively, thus lowering the vertical's "take off" angle.

As the reader might have already deduced, inland terrain--with its poor soil conductivity compared to salt water, topographical undulations and geological formations--does not reflect the negative-angle component well. Whatever energy is reflected off the ground does not recombine constructively with the low-angle lobe because its polarization and phase have been dramatically shifted. That is why verticals do not work as well in regions with poor soil conductivity, or in valleys or cities, compared to when their far fields are proximate to the ocean. When they are, the conductivity of salt water, combined with the ocean's planar surface, enhances the reflection of the negative-angle component of a vertical's radiation. This reflected component recombines with the predominant low-angle lobe a lot more coherently than is the case over land. How much more? Almost all of it. The conductivity of salt water, combined with its virtually mirror-smooth surface, redirects almost all of the negative-angle radiation to the low-angle lobe. This extends the low-angle lobe, while skewing its lower-half downwards towards the X-axis. This causes salt water verticals to exhibit lower angles of radiation than inland installations. 

Salt Water Extends a Vertical's Low-Angle Lobe

To the left, the vertical over land. To the right, the vertical as it is relocated away from the ocean.

***

You can visualize why RF does this over the ocean's surface by remembering what the ocean looks like on a sunny day. If the sun is directly overhead, you can look down into the water and see the fishes swimming around. If the sun comes in at an increasingly lower angle, at some point it starts glittering off the surface and you cannot see down into the water.

The sun's light is as much electromagnetic radiation as is the energy radiated by the vertical. It's just that its frequency is so high, and its wavelength so short, that the contours of the ocean's waves and ripples--which are many wavelengths longer than sunlight's--cause the sun's refelction to glitter and sparkle. In the case of the 7 Mhz vertical, its 40 meter wavelength is much larger than the countours of the waves and ripples of the water. Therefore, at 40 meter resolution, the surface of the ocean appears to be a flat surface exhibiting high conductivity. At 7 Mhz, it acts as a smooth mirror reflecting most of the negative-angle radiation emitted by the vertical. When this reflected component merges with the vertical's low-angle lobe--kilometers out in the antenna's far field--it combines constructively, thus enhancing the low-angle component of the vertical's radiation pattern. Inland, this is not true. Geological formations and topographical undulations are perceivable at 40 meter resolution. They constitute "ground clutter" to the negative-angle component of the vertical's radiation. When encountering the poor conductivity of all soil types, the small amount of this component that makes it way back to the low-angle lobe does not recombine with it. This is why the antenna modelling plots of verticals situated over soil never show the low-angle lobe coming all the way down to the X-axis. 

Richard Feynman & The Pseudo Brewster Angle

http://myweb.dal.ca/fd814764/rte_rtm_plot/

The Brewster Angle is from physics. 1811, to be exact. You can read Dr. Brewster's original peper here. https://books.google.com/books?id=U-U_AAAAYAAJ&pg=PA125&hl=en#v=onepage&q&f=false

The Brewster angle has to do with figuring out what happens when a "pencil of light" (aka. light beam), let's say travelling through air, hits some other medium, like water or glass. When it does, part of the light beam is reflected off the surface of the water or glass, and part of it is refracted by the medium--meaning it passes through the medium. The angle at which the "pencil of light" strikes the medium determines how much of the light beam ends up reflecting off the surface of the water or glass, and how much of it ends up passing through the medium as a result of being refracted by the medium. Another thing that determines the percentages of the light beam that end up being reflected and refracted is the "index of refraction" of the medium, itself. 

Now, when a light beam bounces off of something, or passes through it, the photons don't actually richochet off the substance. Or navigate through it, if the substance is translucent. What happens is that the photons are "absorbed" by the substance. They disappear. They do so by "jiggling" electrons in the substance. This, in turn, causes the electrons to "re-radiate"--just like the passive elements of a yagi do (e.g. director, reflector). But in this case the electrons "re-radiate" by emitting another photon. That's how photons are "reflected" off a substance, or "pass through" a translucent one. It's like a relay race. Photons in the light beam hit the substance and excite electrons in the substance. These excited electrons then emit photons in order to return to their lower energy state. These "re-radiated" photons then almost immediately hit another electron, jiggling it. It emits a photon. This goes on and on and on through the substance until the electrons at the opposite surface of the substance emit photons which do not strike anymore electrons, but simply continue uninhibited outside of the substance. This is an over simplification, and assumes the substance is in a perfect vaccum. But it serves the early stage of our understanding of the Pseudo Brewster Angle.

Now, each time a photon jiggles an electron, certain aspects of the light beam change. One of these asspects is its polarization. As things turn out, assuming the light beam heading towards the substance is not polarized, being reflected by the substance polarizes it, and being refracted by the substance also polarizes it, but not so much. 

the angle the sun has to be to the ocean in order for the glare of its reflection to prevent you from seeing into the water. Or the angle the sun has to be at in order for the glare off a window to prevent you from seeing inside a building. Actually, the Brewster Angle is a lot more intricate than this. Let this simplistic notion suffice on the first pass of a more thorough explanation. Having said that, if the sun gets lower off the water than the Brewster Angle, it glare continues to prevent you from seeing into the water. And if you look closely, you will notice that you cannot see into the water even in parts where the glare of the sun is not reflecting off the surface of the water. The same holds true if you are iunderwater. When you look up amd away at a certain angle, you cannot see the sky above you. All you see is a rippling reflection of everything beneath the water. If you look straight up, it disappears and you can see clearly the sky above. You can see the same thing when looking into an aquarium. The Brewster Angle is the angle at which total reflection occurs. 

Reflection of turtle off surface of water is due to the Brewster Angle

WORKING ON THIS SECTION NOW:- 

The Pseudo Brewster Angle is a spin-off found used in RF engineering. Technically, it is the angle at which the lower-half of the low-angle lobe is 6 dB less than its maximum value. 

Below this angle. the reflected copmponent of the negative-angle radiation does not constructively recombine with the low-angle lobe. This is why angles lower than the Pseudo Brewster Angle show the radiation pattern receding away from the outer ring on antenna plots. In other words, below the Pseudo Brewster Angle you will see the the low-angle lobe getting weaker and weaker. Above the Pseudo Brewster Angle, the plot will show the low-angle lobe getting stronger and stronger. This is because above the Pseudo Brewster Angle, the reflected component of the negative-angle radiation recombines constructively with the low-angle component far out in the antenna's far field. This enhances the low-angle component of the vertical's radiation pattern. For DXing, we want the Pseudo Brewster Angle to be as low as possible to maximize the lowest-angles of the antenna's "take off" lobe. This causes the front of the outboard motorboat discussed earlier to level off so close to the X-axis that it appears to be sitting flat on the water. And this is exactly what the bottom edge of the vertical's low-angle lobe looks like when plotted over a perfectly reflecting plane. When the same modeling program is set to model the vertical over salt water, the outcome is practically the same; the low-angle lobe begins to drop off at 0.1 degree! The takeaway is that the Pseudo Brewster Angle is determined by the far field of the antenna. The lower the Pseudo Brewster Angle, the more the bottom edge of the low-angle lobe hugs the X-axis. Which means more energy radiated at the lowest possible angles. Which means the fewest possible hops to the DX location. 

REVIEW OF ELEVATED COUNTERPOISE SYSTEM

The Ground System Determines How Much Power is Radiated by the Vertical

Introduction

An old timer summed up the role of a vertical's ground system when stating, "It determines how much power the vertical radiates". Another well-known ham equates the ground system as a footing needed by the transmitter to "push against" when jiggling electrons up and down the vertical element. Others visualize the ground system as a path allowing for "return currents" radiated by the vertical element to make their way back to the shield of the coax. Anyway you slice it or dice it, the ground system for Marconi-type antennas, such as verticals, is crucial. For the verticals that do work well, the operators all testify to the enormous amount of physical work requred to errect them. And this effort is unequally divided between installing the vertical element (easy) and constructing the ground radial system (hard). Again, most of the time you will spend in the field will be consumed by installing the ground system. There is a lot of talk in the community about using elevated-radials as a short-cut around putting in buried radial systems. As few as 2 elevated radials are said to be sufficient to extract some modicum of performance from a vertical. 4 elevated-radials are heralded as working as well as 32 buried radials. I think such observations might hold true when the vertical is installed near salt water. Yet, when installed inland, verticals with 2 or 4 elevated-radials did not work as commonly described. I had to get to 15 elevated-radials before the vertical started to behave in the field as it is supposed to on paper. And it took 15 elevated-radials before the signal reports I received started to approach those of fully-developed vertical systems. 

So I thought it would be interesting for the reader to examine the various stages of the elevated-radial system I incorporated over a period of several months, as seen in the photographs below. Part of what is evidenced in this review is the progression of my own view about the ground system from an initial disregard for it, to an almost obsessive fixation for it. My take-away from all of this work is that the ground system is the aspect of the vertical antenna system which rewards hard work with improved performance. And when I think back on this realization, I cannot understand why it was not apparent to me at the beginning. This is because installing the vertical is not hard to accomplish. It's relatively straight-forward. And since there are no "free lunches" in antennas, to get the vertical to work as well as it is supposed to, additional labor had to be focussed on some other part of it. And that part turned out to be the ground system. 

Our review starts with the photographs below depicting the full-sized vertical mounted to the back deck of the home QTH in early March. The same two elevated-radials used for portable operation at seaside locations are used as a coounterpoise for the full-sized vertical. That is the whole ground system at this point. Two elevated radials. 

You can see the simple means used to connect the elevated-radials to the shield of the coax, consisting of a bolt mounted to the bottom of the PVC insulator. Nothing more than that is required. A wingnut is run down to tighten the electrical connection, as well as to enable the radials to be removed without any tools. A couple makeshift PVC poles are stuck into the (soggy) ground to support the ends of the radials. Aside from the mathematical miscalculations already covered--which cause difficulty in tuning the vertical--the signal reports received from on-air operation are disappointing. Not much power is being radiated by this set up. 

So I relocate the vertical to the Test Range 150 feet behind the QTH in the woods. I double the number of elevated radials from 2 to 4. This lowers the vertical's feedpoint resistance. But the reports from DX stations are disappointing. And this is with 4 elevated radials! This is supposed to be equivalent to 32 buried radials, according to eHam chatter. No joy here. So I move on. 

You can see that I have yet to develop respect for ohmic losses associated with the connection of the radials to the shield of the feedline. I simply kept stacking radial wires to the binding post at the bottom of the PVC insulator. And, of course, there is no effort to reduce common mode through use of ferrite beads. It got to the point where I could not run down the wingnut sufficiently to get a decent DC electrical connection, let alone a low-loss RF connection. Take a look at how messy this is. 

I double the number of radials again, this time from 4 to 8. This is more than what the common literature calls for, and uses up the rest of the speaker wire in my junkbox. At this point I cannot stack the new wires on top of the old ones around the ground stud. I try it, anyway. At this point the lightbulb goes off in my head, providing the first glimmer of the eventual realization that the ground system is "where it is at", so to speak. So I add a circular ground bus wire to the grounding post. It is made of AWG #12 solid copper, and encircles the base of the vertical. Scraps of PVC lying about the work shop are recycled as stand-off insulators. The thing works. I can even remove it by pulling the PVC tubes off the PVC end-caps. I transfer all of the elevated radials thus far acquired over to this new contraption. I solder them with a propane torch. So far in this review, we have seen the system start with 2 elevated-radials. And then four. Now we are up to eight, with an improvement in the means of making the base connection. 

Although the feedpoint impedance gets closer and closer to 36 ohms, and the SWR/reactance curves continue to align themselves closer to textbook theory, even with 8 elevated radials the vertical's performance is not nearly where it should be. When calling CQ DX above 7175 Khz, I am getting responses from General class hams reporting that I am extremely loud. But the DX reports I seek still elude me. By this point my comparative reports are derived from daily contact with a group of Bulgarians on 7164 Khz, and by piggy-backing VE9ZY, Mac, who has taken an interest in the project. Mac runs a pair of phased verticals, each with 120 buried radials. We are both runing comparable power. But the difference in signal reports from DX stations--with mine being 30 to 40 dB lower than VE9ZY's--is tremendous, and cannot be attributed to Mac's forward gain or the near field efficiency of his buried radial system. A significant portion of the discrepancy is due to my inefficient ground system. I conclude that eight elevated radials are not enough to recover the ground losses encompassing the Test Range out in the woods.

I randomly begin stringing radials in any direction that harbors an anchoring point, using AWG #26 enamel magnet wire because my speaker wire ran out. When I get up to around 18 elevated radials, things take a turn for the better. The feedpoint impedance is 36 ohms, and with the SB-221 input tuned circuits optimized for the exciter, I can now use the Murch transmatch between the amp's output and the feedline in the shack. This enables me to pump more power into the coax, which is showing a pretty hefty SWR at the transmitter end. None the less, DX signal reports are picking up. One special night Italian hams, who have been watching the project, excitedly advise me to "not touch a thing" for my signal is 20 dB over S-9 in Rome. It appears soldering the radials to the ground bus wire, and increasing them to 18 is stabilizing the system. The vertical is starting to behave as the textbooks predict. And the SB-221 finally sees a 50-ohm, non-reactive load via the Murch tuner. I make a mental note that the ground system is key to getting the vertical working correctly, and that I will be doing a lot of work on it during Phase III of this project. For now, however, the vertical is operating decently. And I can now spent cold, winter nights at the helm of a high-powered station working DX on 40 Meters from the sanctity of a New England workshop.

Moving this story about the ground system ahead at a faster clip, after getting the first (West) vertical operating with 18 elevated radials, I turn my attention to constructing the second (East) vertical. I applied the lesson learned on the first vertical to the installation of the second. I use a ground bus and #26 enameled magnet wire to string up about 15 elevated radials. I have yet to discover the error I have been making when calculating 1/4 wavelength on 40 meters, so I cannot get either vertical to resonate at the target frequency of 7150 Khz. The good news is that they resonate around the same frequency: 7450 Khz. The second (East) vertical goes together a lot easier, and looks a lot cleaner electrically in the end. Perhaps because of this, it's feedpoint impedance is a lot closer to 36 ohms than the first vertical. I make a mental note to clean up the rats nest of ground wires on the first vertical, making sure to use the same wire type when doing so.

Accelerating this description of the ground systems, I end up ripping out the AWG #12 ground busses, and replacing them with AWG #6 solid copper.

I then rip out all of the speaker wire and #26 enamel wire radials, restringing them with AWG #18 stranded copper ($33/500'). This makes a huge difference in DX signal reports. I pick up about 15 dB. 

25 Elevated Radials • East & West Verticals • Symetric Distribution • AWG #18 Stranded • DX Signal Reports Up 15 dB

When installing the #18 stranded copper radials, I measure each to the same length, +/- 1". Initially I string 15 per vertical. But then I went back and installed catenary lines around both verticals, which took about a week. I was then able to re-re-string the #18 radials, setting them out in a symeterical pattern from the bases of each vertical. And then I went back over the next 2 weeks and added more. I added insulators while so doing, and spaced all points of intersection with 6" PVC tubes. 

I ended up using 1,500 feet of AWG #18 stranded copper wire for 30 elevated radials per vertical. I then went through the several steps needed to resonate the phased vertical system, beginning with resonating each vertical +/- 5 Khz while the other was disconnected from its feedline. Then I did it again, this time while the other vertical had a 50 ohm non-reactive load (resistor) connected to its feedline. And then I did it a final time while both verticals were connected to their respective feedlines. To adjust the verticals to resonance, I had to unbolt the ground bus and pull the PVC stand-offs from their end caps. 

In the end, I picked up between 20 to 25 dB in signal reports from DX stations--compared to when I started with 2 elevated radials. I accomplished this partly through a methodological, and, at times, stumbling development of the elevated counterpoise system, and partly through improving the efficiency & impedance matching of the feedline system. Additional increases were obtained by matching the exciter input with the SB-221 amplifier and tuning of the array's phase delay & impedance-matching lines. Removing the transmatch at the end, after obtaining a non-reactive 50-ohm impedance at the transmitter end in the shack, also assisted in system performance. Finally, final tuning of the two verticals after installation of the elevated counterpoise system added about 3 to 5 dB of the overall system gain. I suspect raising the phased vertical array from 4 meters to 8 meters above ground would further enhance performance, although I will leave that task for the end of the summer. Below are photographs depicting the phased verticals in their final form, although the photographs were taken before number of radials reached 30 per vertical. 

Two phased verticals can assume three directive states. For the sake of this discussion let these three states be called East, West and Omni. The three states require two relays in the remote switching box: one to toggle East/West, and another for omnidirectional operation. We will leave for later consideration the question of whether or not to isolate coaxial shields, which requires more relays, and assume the shields are connected to simplify wiring of the remote switching box. 

Altering Phase on Receive

Phased verticals exhibit directivity due to a difference in the phase of the signal exciting them. This is true for receive and transmit. In the case of receiving, the phase difference varies in accordance with the compass heading of the arriving signal. If it arrives at the front of the array, the induced phase difference adds the signal up, making it louder. If the signal arrives behind the array, the phase difference cancels the signal, making it weaker. Gradations between the two extremes are distributed over intermediary compass headings. How great are the two extremes? A signal arriving in front of the array is increased by a factor of two (3 dB), whereas a signal arriving behind the array is reduced by several orders of magnitude, e.g. thousands of times (20 - 30 dB). Thus it can be seen that a phased vertical system is not a high-gain antenna; it only doubles the strength of signals arriving at the front (0-degrees). Yet this enhancement is dispersed over a wide swath (+/- 80-degrees), after which signals drop off precipitously towards the rear (180-degrees). In practical terms, a pair of phased verticals on the East Coast will enhance reception of European, African and South American signals by about 3dB--if oriented East/West--against a background cleared of stateside QRM and QRN by 20 to 30 dB. On cold winter nights, a pair of phased verticals on the East Coast produces an astounding listening experience. 

Altering Phase on Transmit

For transmitting, the phase difference is created by various means of electrical wizardry. The Christman method, amongst others, accomplishes this by inserting an extra piece of coax into one of the vertical's feedlines. This compells the transmitted signal to travel down a longer feedline, thus retarding its arrival at one of the verticals. The amount of retardation constitutes the phase-shift between the verticals--expressed in degrees of the signal's 360-degree oscillation. Since the purpose of the extra piece of feedline is to delay the transmitted signal, it is called a "delay line". It's length is measured by the number of degrees the signal advances in it's oscillation during the time it takes the signal to travel down the delay line. Interestingly, delay lines are measured in units of time, not distance. And these units of time, in turn, are not measured in seconds, but in degrees of a complete, 360-degree oscillation. Since our array requires a 90-degree phase-shift, the length of our delay cable will be equal to how far the signal travels down the cable while it progresses 90-degrees, or 1/4, of its oscillation. As you might suspect, the 90-degree delay line ends up being 1/4 wavelength long. Equally uninspiring might be the realization that a "180-degree delay line" is 1/2 wavelength long, and that a "270-degree delay line" is 3/4 wavelength long. And, yes, we do have to take into account the velocity factor--but not until we are finished with all the theoretical calculations. In other words, don't even think about the velocity factor until you find yourself in the field with the wire cutters in your hand.

Cutting Delay Lines: Some Practical Tips

It is important to get into the habit of thinking of distance in terms of time when discussing phased arrays. You will find this to be true whenever delay and feedline lengths, as well as inter-element spacings, are conveyed during such discussions. Phased-array experts appear to think of space as time measured not in seconds, but in the number of degrees a signal advances in its oscillation as it moves through physical space. This type of thinking transposes one-wavelength into 360 degrees, 1/2 wavelength into 180 degrees, and a 1/4 wavelength into 90 degrees. I reiterate this point despite the reader having presumably grasped it due to the following quandary; namely, what happens if you need an 84-degree line? Or a 71-degree line? How many feet is that?

To answer this question, let's suppose you're assisting an RF engineer constructing a phased array in the field. And he asks you to cut an 84-degree line of coax. What do you do? One approach is to reformulate his request as meaning he wants you to cut off part of a 1-wavelength cable, which you know is 360 degrees "long". And that he wants 84 degrees of it--or "84 parts out of 360". So, you divide 84 by 360 (on your iPhone) and get .2334. You then calculate how long 1 wavelength is in feet (936/f), and multiply it by .2334. This gives you the 84-degree "long" cable the engineer wants. After measuring it out on the ground, you hover over it with your wire-cutters. But then you abruptly stop. Why? Because you remembered to figure in the velocity factor!

Actually, you don't have to do that if you have an antenna analyzer. You can go ahead and cut the coax because the velocity factor, which is always less than 1, guarantees the final length will be less than the amount of feedline you've measured out. And then trim it to the precise length using an antenna analyzer, as covered elsewhere in this tome. How much will you end up trimming off? If the velocity factor is .84, which it oftentimes is, about 1/5th of the coax will be trimmed away. For a velocity factor of .66, it'll be about 1/3. If you don't have an antenna analyzer, now's the time to apply the velocity factor and make the final cut, adding on a couple of extra inches in case you screw-up putting on the connectors. Done. Close enough for government work. 

Wiring the Remote Box

Remembering that the shields are all tied together, let's examine how to wire up the remote relay box used to switch the directivity of the array. We'll start with the layout and physical lengths of cabling, as provided by Figure 2, below.

Figure 1

Phased Verticals Using Christman Phasing Method

A major aspect of the Christman phasing method is that it doesn't use a 90-degree delay line. Instead, a 71-degree delay line is used in conjunction with two, 84-degree feedlines connected from the switching box to either vertical. This technique produces the 90-degree phase difference between verticals while distributing power equally between them. Use of T-connectors to connect the 84, 71 and 84-degree cables to each other in that order simplifies the wiring of the remote switching box, to which the T-connectors are attached by means of SO-239 connectors mounted either side of the box. This enables the 71-degree delay line to be neatly coiled and suspended from the remote relay box which is mounted between the two verticals, to which the two 84-degree feedlines are respectively connected.

Operation

When the remote switching relay connects the main feedline to the first T-connector, the first vertical gets fed through its 84-degree line while the second vertical gets fed through its 71 and 84-degree lines. This causes the signal radiated by the second vertical to lag behind the signal radiated by the first. When the relay connects the main feedline to the second T-connector, the second vertical is now being fed through its 84-degree line while the first vertical is being fed through its 71 and 84-degree lines. This causes the signal radiated by the first vertical to lag behind the second vertical. This reverses the directivity of the array--which beams towards the vertical that has the extra coax in its feedline. 

Construction Tip: Wire up your remote switching box so that the extra coax is added to the vertical pointing towards the DX region you work most. This will cause the phased array to point in this direction when there is no power sent to the remote relay box.

A second relay shorts out the 71-degree delay line, causing both verticals to be fed through 84-degree lines. This causes them to radiate in phase, which produces the omnidirectional pattern. 

Whether or Not to Isolate the Elevated Radials

At some point you need to decide whether or not to tie the elevated radial systems together wherever they intersect. You can wrap wires or solder them at their intersecting points, or electrically isolate them with insulated spacers. I opted to isolate them with 6" PVC spacers because a footnote I read in a technical paper indicated that doing so adds about .75 dB to the array's forward gain.

Keeping the elevated radial systems electrically isolated necessitates lifting the shields of the coaxial cables at the switching box. This, in turn, requires relays to switch the shields along with their respective center-conductors in accordance with the various configurations just described. Using a plastic box isolates the SO-239 connectors. However, if you use a plastic box in a system that ties the shields together, grounding the SO-239 connectors with a piece of wire introduces a reactive component which degrades the array's performance. The workaround is to either (i) ground the SO-239 connectors with a copper or aluminum strap, or (ii) use a metalic box for the remote relay enclosure.

Purists can employ plastic boxes in which relays switch coaxial shields along with center-conductors. If you are using low-power, a single DPDT relay can be tasked to switch the array's directivity East-West, and another DPDT used to short out the delay line as described. For higher power ooperations it might be advisible to double-up the contacts of a DPDT relay to increase it's power handling capabilities. If you opt for this approach, you will need two (2) DPDT relays with the shields all tied together, and four (4) DPDT relays for the ground-isolated configuration.