DECEMBER 27, 2018

Matching Vertical Feedline Impedances

L-Match in the Feedline

As we tune the experimental vertical its feedpoint impedance changes, progressing lower as its resonant frequency rises. With 25 radials deployed, the vertical's impedance and resonance is not within comfortable ranges for the amplifier. To temporarily correct for this in the shack, a L-match has been inserted into its feedline allowing a 50 Ohm impedance with zero reactance to be presented to the amplifier. 

L-Match for Experimental Vertical Installed in Shack

Shows 50 hm impedance and zero reactance to amplifier when experimental vertical is being fed
No need to re-tune vertical while radials are being deployed. 

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Another L-Match in the Other Feedline

A second L-match has been constructed to take care of the impedance transformation for the reference vertical. Matching the impedances of the two verticals to 50 Oms and zero reactance eliminates the possibility that a mismatch to the amplifier affects results of A/B comparison of the verticals. 

L-Match for Reference Vertical Constructed & Installed

Provides 50 Ohm impedance and zero reactance to amplifier when experimental vertical is being fed. 

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More comparisons performed tonight. A71AM reported 3 S-units in Qatar. Ireland reported no difference and then 2 S-units differnce over span of 20 minutes. 

System Used to Switch Between the Verticals

Both vertical feedline impedances can be independently set to 50 Ohms before being switched to the amplifier

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DX data below.

DXSummit Spots • December 27, 2018

NOTE: Propagation fluctuated from low to high angle in a matter of minutes. 

Check out the wide variety of compass headiings reporting in, characteristic of an omnidirectional radiator.

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DECEMBER 26, 2018

Salt Marsh Vertical Begins to Outperform Reference Vertical • Massive European Daylight Pile-ups • VK7 Eavesdrops for 4 Hours

Good morning. 

Eastern Grayline

The view from the operating position this morning.

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Salt Marsh Vertical Begins to Outperform Reference Vertical

1 to 2 S-units on Long-Haul Grayline Contacts • No Difference Stateside

The experimental salt marsh vertical has begun to pull away from the reference vertical in terms of signal reports received over grayline propagation paths. This appears to be the result of the continuing addition of ground radials in the marsh. When we arrived at 15 radials, the two aerials were neck-to-neck. After that, by 25 radials, South Africa, for example, is reporting 1 to 2 S-units difference. Meanwhile, stateside stations do not report any significant difference, which suggests both verticals exhibiting identical higher-elevation patterns.

Two, massive European pile-ups have thus far been generated since the last update, the first continuing well past daylight in Europe, as detailed below.

Here's the DXSummit data for the EU pile-up the day prior:

Australian Eavesdrops for 4 Hours

QRZ.com reader listens to EU pile-up while working in the shack on a summer afternoon.

During the European Pile-up, Rod, VK7FRJG in Australia, was working in his shack "down under" listening to the fracas for four (4) hours! He was able to break the pile-up a couple times and then sent a nice email, reprinted below. His report gives us a good idea of how the experimental vertical is playing over a period of several hours on the opposite side fo the world. 

Added More Radials to Experimental Marsh Vertical • Station Upgrades

25 Ground Radials At Present • Improving TX Audio • Adding On-Air Recording and Playback Capabilities

Did not have much time at the end of the day to do any antenna work, and only managed to lay down five (5) more radials in the marsh. Did work on the audio quality by replacing the ELECTROVOICE stick microphone with a 1960s UHER M517, requiring external equalization to cut lows. After sundown am configuring soundboard to record and playback signals for posting on The Saltwater Vertical Sound Archive. Check it out.

DECEMBER 25, 2018

Merry Christmas • Laying Ground Radials Down in Salt Marsh

SCIENTIFIC NOTE: A/B comparisons between the reference vertical on the deck and the salt marsh vertical resulted in stateside stations seeing no difference between the two, while long-haul DX stations consistently observing 1 to 3 S-units difference. Especially along long=path, grayline propagation conditions. We think that this means the higher-angle envelopes of both verticals are similar, whereas the experimental vertical in the salt marsh is exhibiting a protrusion in its lower elevation envelope. We would need a couple more hams over here and a drone equipped with a field strength meter to procure serious empirical field data. Since we don;t have these resources, we will follow the Old School example by just having fun collecting our non-empirical data through on-air reports. By the way, if anyone has a drone, try to figure out how to rig it up to make field strength measurements through use of something like an Adrino. That would be a cool tool. 

Second Day of Radial Deployment

2nd day of laying 30 ground radials out beneath the experimental vertical in the salt marsh. We are trying to reduce feedpoint impedance to the 36 Ohms exhibited by a 1/4 WL vertical over perfect ground. After laying down 10 ground radials yesterday afternoon we reduced the feedpoint impedance from 52 to 41 Ohms! That's 6 Ohms of ground loss which translates into an efficiency figure of 85%! Working on more radials this afternoon in the mud wearing waders. Continuing A/B testing tonight. Lots of data being collected. 

20 Ground Radials: Vertical Resonant Feedpoint Impedance 

Impedance same as 10 radials • Resonant frequency raised 64 Khz.

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A few hours later, after installing 10 more ground radials in the marsh...

20 Ground Radials: Resonant Feedpoint Impedance

Impedance same as 10 radials • Resonant frequency raised 64 KHz.

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Here's the sweeps for 4 ground rods versus 20 ground radials, which seems to indicate we are headed in the right direction. Note that the readings do not take into account the tide charts. Having said that, both sets of readings were taken at low tide, obviously, since I was working down there. It is impossibel to do so at high tide without waders. And even then one would not undertake such a venture for you cannot tell where you are stepping beneath the water. 

SWR & Reactance Sweeps • Ground Rods vs 20 Ground Radials

Low tide

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UPDATE: DECEMBER 23, 2018

Experimental Vertical Repaired and Tuned • Experimentation Begins Tonight

This morning I corrected the problem and retuned the test vertical in the marsh, as seen below. 

"Radial-less" Saltwater Marsh Vertical SWR Sweep

52 Ohm feedpoint impedance at resonance,16 Ohms ground loss. 

50% efficient without radials. SWR under 1.2 across band.

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Remember, a 50 Ohm feedpoint impedance on a 1/4 WL vertical means about 14 Ohms of ground loss since the optimum feedpoint impedance for such an aerial is 36 Ohms. So what we learned thus far is that four (4) short ground rods (2.5 feet long) spaced 4' apart around the vertical produced 16 Ohms of ground loss at resonance. Another finding is that it is possible to resonate the vertical against the ground rods, e.g. the reactive component is manageable at resonance. The only other thing to find out is whether or not the aerial will survive high winds. So we are looking forward to A/B comparisons between the two verticals on-the-air.. 

Once again, here she is. Standing tall and proud. The center of her is double-walled aluminum stiffening her in the winds. 

DECEMBER 22, 2018

Second Vertical in the Salt Marsh.

First off, check out the view from the operating position and deck this morning! Lots of rain yesterday. We were able to install the second vertical in the saltwater marsh this afternoon. She went up beautifully, despite strong winds, and rides well after being guyed. The ground system consists of the four ground rods depicted in the previous update, slammed down into the mud. AWG #10 wires bond the ground rods back to the support pipe. She tuned to a 52 Ohm input impedance with 4 Ohms of reactance at 7.190 Mhz! An hour later everything changed as the water receded with the tide, apparently causing the vertical to resonate at 8 Mhz! I guess we need to just install the ground radials tomorrow!

The Next Day...

Whoops! Correction. After lengthening the vertical to bring it to resonance, the hose clamp used to tighten the junction slipped, causing the vertical to slip back down in itself, throwing the resonance back up to 8 Mhz. How did this happen? I got so excited after tuning the aerial that I went back inside and tried it out, rather then returning in what available light remained to finish the job by drilling a hole to set in a sheet metal screw. So the vertical slipped back down inside it's telescoping self after a little while in the blowing winds, and raised its resonant frequency by so doing. I realized this the next morning when sipping a cup of coffee on the deck admiring the vertical, and then spitting out a mouthful when I noted the guy lines were all slack. I fucked up on that one.

Am going out to correct this now so we can finally A/B between ground rods and radials this evening. 

DECEMBER 20, 2018

55 Degrees in December? Time for Antenna Work!

Super warm today. Did a lot of work out on the deck preparing the second vertical for installation out in the saltwater march using four (4) ground rods stuck in the mud, rather than a radial system. Let me take you through the progress made today, as photographed below. And, yes, it was fun! 

Good Connections Reduce Loss

I got a bunch of new coaxial connectors and installed them on the ends of the RG-8X feedlines we were using with the phased verticals at the previous QTH. That was a good thing to do because you can experience significant losses through bad connectors. And it was about time to replace the ones we had been using: God knows how far they were degraded by all the RF we had been pumping through them. 




We also finally installed the RG-8X adaptors, which makes the connection more robust and weatherproof. A lot neater way to make the connection. And one which lessens the likelihood of melting the insulating material in the PL-259, which I often do by applying the soldering iron to it too long.

Extra Coax

Below is the center guy ring for the second vertical made from a PVC tube with cable ties epoxyed to it.

PVC Guy Insulators

Joining Vertical Sections

We're going to need that, and probably a second, higher one, on the vertical in the marsh. The winds off the ocean are not abated by any structures or local topography. Depicted to the right is way of securing the junctions in aluminum verticals when you don't have the right series of tapering tube. In this case I have a smaller diameter tube inserted between two larger ones, which butt together under the hose clamp. Set screws prevent vertical sliding after final install and support electrical conductivity. This is the almost-completed reassembly of the second vertical.n this case I have a smaller diameter tube inserted between two larger ones, which butt together under the hose clamp. Set screws prevent vertical sliding after final install and support electrical conductivity. 

Second Vertical

This is the almost-completed reassembly of the second vertical. The base insulators are PVC tubes fastened to the base pipe with electrical conduit hangers. You can easily detach the verticals after install. It is a strong and cheap way of securing vertical radiators. 

Copper Pipes

Here's the ground rods being prepared.  I use Liquid Electrical Tape to protect the connection from the weather to keep Ohmic losses down. I'd solder the sumbitches but I don't have a propane torch right now. 

Here's the fitting of the current bead balun to the base support pipe. The balun is one sold by The Wireman ($14) consisting of 50 ferrite beads strung along a piece of RG-173 super thin, albeit high-power, coax.

Detail of Current Balun "Capsule" Mounting

An electrical conduit bracket fastens the PVC tube to the base pipe.

The PVC tube contains a Wireman current (bead) choke ($14)

 

DECEMBER 18, 2018

Outstanding Initial Transmitting Session!

Incredible evening barefoot with 100 Watts. The MFJ Analyzer tells me the 1/4 WL vertical is good for transmitting, which I did not expect; I only put it up to be able to listen to the bands. So I tuned up into it and enjoyed a 7+ hour session on the air from the saltwater marsh using 100 Watts. I worked into Europe until noon, European local time. Thank you everybody for the enormous pile-ups! We're going to have fun from this location. 

When I woke up for work, it was blowing heavily -- gusts coming in from all directions, causing the 1/4 wavelength vertical to dance like a VooDoo Child. I guyed it with parachute cord to insulators to cable ties.

Calm Descends over Salt Marsh
This is the only antenna in use

Not much, but it works great. And, again, that's because of the location; this thing doesn't even have a serious ground radial system, as illustrated below. 

All I got out is four or five of these radials unwound and thrown off the ends of the deck. Since this produces a feedpoint impedance of 66 Ohms, and the optimum 1/4 WL vertical feedpoint impedance being 36 Ohms, that means we got about 50% efficiency with this contraption on the deck. When I deliver 100 Watts to it, the far field gets 50 Watts to sculpt.

What a Mess
Only 4 or 5 counterpoise wires are unrolled
and thrown over the deck railing.

For it is in the far field that the radiation pattern of an antenna is shaped, not the near field immediately surrounding the antenna. And this includes the final take-off angle, which many operators strive to keep low to maximize their signal reports at distant locations. 

When we take a look at the mess underbneath the vertical, above, we realize there are no means to effectively collect return currents emitted by the monopole radiator. Despite this fact, the signal reports being received and sent are astonishing. This is likely because the far field is a saltwater march adjacent to the Atlantic Ocean to the South and a mile to the East. That is the first lesson we are learning in this second phase of our antenna experiments. Should you come across this signal on 40 Meters, remember it is being radiated by an aluminum pole stuck out on the deck with the mess seen above serving as the counterpoise. In a moment we will install the second vertical in the salt marsh and A/B between the two antennas to see if there is any difference. 

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DECEMBER 12, 2018

Writing Book About Verticals from a Salt Marsh Next to the Sea

Compliments of a local family, I am installing the station in an unoccupied house next to the ocean to write Saltwater Verticals & Phased Arrays, a book about verticals on the 40 Meter band. The most-recent updates, appearing below, are research for the chapter about installing a pair of phased verticals in a salt marsh, and then unleashing them on the 40 Meter band. Saltwater Verticals & Phased Arrays provides readers with a more detailed exposition of theroretical and technical matters covered on this popular QRZ.com page. Thank you everybody and enjoy! 

No antennas up yet, but with 1/4 vertical mounted on the deck with 2 radials thrown over the railing I can hear Europe at 2 PM in the afternoon on 3.5 and 7 Mhz, and easily listen to AM broadcast radio stations in Chicago after sunset. We will now continue our antenna experiments, striving to achieve the following scenarios:

Phase I: 7 MHz Reference Antenna
Let's put up a 1/4WL vertical in the deck with a few elevated counterpoise wires as a reference antenna for future experiments.

Phase II: 7 MHZ Vertical in the Salt Marsh Without Any Radials
Let's see if there is any truth to the wive's tale that there's no need for radials in salt water.

Phase III: Ground Radials Vs. Ground Rods
Let's see what happens when the A/B a vertical in the salt marsh operated against ground rods versus ground radials. Will one be stronger than the other?

Phase IV: Phased Verticals in the Salt Marsh
The ultimate situation cited in engineering textbooks, let's see how well a pair of phased verticals work when installed in a salt marsh next to the sea.

Phase V: Does The Skin Effect Matter?
What happens when the ground radial system under 7 MHz phased verticals is submerged under salt water 1" to 3". Is there any improvement in performance? 

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