Pivoting Vertical Tiltover Mounts

Vertical Tiltover Mount Pivot
Uses aluminum insert.

Yesterday witnessed the completion of the Saltwater Vertical Tilt Over Project with the installation of the second mount in the Northeast vertical. All went smoothly, the job taking about 30 minutes. When completed, the vertical could be raised with one hand, and then locked into place with a bolt. The contraption is a perfect solution which also simplifies the mounting of the PVC capsules containing the ferrite-bead and static discharge chokes: a sheetrock screw holds the metal bracket to the timber. The contraption also lowers the visual impact of the antenna system by minimizing use of white PVC tubes with the wooden supports blending in with the browns and tans of the Marsh. 

One of the modifications to the Tilt-Over System® is the introduction of an aluminum tube inserted through the lower connection point. I cut one yesterday from aluminum tubes procured from the ScrapYard before heading out to the field. What happens is you insert this short section of aluminum tube through the timber and ground pipe holes, cutting the end off so that it is flush with the ground pipe. Fender washers are sandwiched between the timber and the ground pipe. When a carriage bolt is passed through the aluminum tube and tightened, it compresses the tube rather than the timber to the ground pipe. This creates a strong lower mount which also pivots. Stacking fender washers between the two adjusts how far out the tube emerges from the ground pipe, and thus adjusts the tightness of the pivot.

Design Notes: Vertical Feedpoints

When I was outside yesterday investigating the problem with the verticals, one of the first things I did was to check their feedpoint impedances at resonance. This constitutes the first "Y" in the diagnostic logic tree, telling me whether or not the problem is with the aluminum verticals. When I checked with the MFJ 256B antenna analyzer, they were both perfectly tuned to 7.1 MHz, exhibiting zero reactance and 40 Ohms of impedance. This is where I set them after cleaning them over a month ago. Which means they are 90% efficient. 

It is likely that the 4 Ohms of ground loss is partially due to the means through which I connect the ground systems to the coaxial feedline. This connection is a bolt squeezing two large ring terminals (soldered to the ends of 1/4” copper tubing loops) sandwiched between which being wires leading to the coax shields and static bleed RF chokes. On the Northeast vertical, this connection by necessity gets swamped twice a day by saltwater. Not having a NSF grant, I am using what hardware is available in The Parts Department. And in this instance that means a steel wing nut to compress the connection. And that sumbitch gets rusty immediately after deployment. 

The center conductor connection can also stand improvement. Or perhaps replacement after 3 years of service. Its design merely replicates the design I came up with for the portable vertical. What happens is the center conductor connection serves two purposes. It acts as a mechanical stop for the aluminum tube in the PVC insulator tube. While also making the electrical connection between the center of the coax and the tube. This is done by inserting a stainless steel screw through the aluminum and PVC tubes, making sire to drill the hole through the PVC tube larger than that required for the stainless steel screw. This allows for the lacing of two aluminum standoffs on either side of the screw which, when a nut is run-down on the screw, squeeze against the aluminum vertical tube from either side of the the PVC tube. The center conductor of the coax is tightened down on the stainless steel screw with a second nut. This constitutes the electrical connection to the aluminum vertical. Naturally, I am using steel nuts which quickly corrode. And after years of service, the aluminum standoffs are in need of burnishing. Or I can just redesign the whole connection, which is what I did in the tilt-over design.

In the tilt-over contraption, we no longer require the PVC insulator tube to support the vertical tube and ground ring, as originally devised in the portable and elevated phased vertical applications. Instead, the vertical extends below the base PVC insulator so that a brass machine screw and wing nut can provide electrical connection to the center of the coax. To prevent vertical slippage, a hitch pin passes through the aluminum and PVC tubes at the top of the base insulator.

I would like to relocate the verticals deeper into the Marsh. Moving them over to the South a bit, and then deeper into the Marsh to the East. To do this what I would do is not touch either vertical; leave them right where they are. Instead, I would meticulously and anal-compulsively build two ground radial fields out of aluminum electric fence wire. This would mediate the corrosion problem if aluminum hardware was used at the bases of the verticals,

BILL W1ZY

HALLICRAFTERS S40-A RESTORATION

Detailed & Photographed at the bottom of this page

Photos & details at the bottom of this page.

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"I saw your very nice restoration on QRZ.com. I was given a S40 along with a S-meter. I have shipped the S-meter to you. I thought it would be a good addition to your restoration !!!"

John Discenza, WB2NEW

SB-220 ALC MODIFICATION

Variable ALC for Legacy Amplifiers
Modernized for solid-state rigs

SB-220 Equipped with PTT/ALC Connector & Variable ALC Threshold Control

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Reversible Beverage

7 MHz AFRICA-PACIFIC BEVERAGE

2-wire reversible Beverage • Scroll to bottom of page for details

No matter how you slice it, signals coming from either direction are coupled to the feedline through several transformers. To optimize the electrical balance required by the switchable Beverage, it is a good idea to wind the primaries and secondaries in the same direction, and to keep track of which wires are which. An additional transformer making the final 70-to-50 Ohm match between the RG-6 and the receiver in the shack further assists the operator dig weak signals out of the noise, but not by much. ;)

Fiberglass Spacers Made From Snowplow Sticks

F/B Demonstration Video

Half-Square Antenna

Before: dipole.

After: Half-square

A half-square exhibits a low take-off angle without the need for ground radials or counterpoise wires. One way to picture it is to imagine two 1/4 wavelength verticals spaced one-half wavelength apart fed in-phase. This produces a bi-directional "8" pattern broadside to the array. The horizontal wire across the top is the 1/2 wavelength phasing line between the tops of the two vertical legs, and does not contribute much to the radiation pattern. When electromagentically excited, current maxima appear at the top corners and voltage maxima at the bottoms of the two vertical llegs, which must be kept out of reach of humans and animals. The aerial is tuned to resonance by adjusting the lengths of the vertical legs rather than by adjusting the horizontal "phasing" line, which should be kept to the dimensions provided by mathematical formulae. You can cram it into limited-spaces because it is not finicky with regard to the proportions of its dinensions. For example, if you don't have the 36 to 40 feet of vertical height it requires, you can slope the legs off to the same side, or tuck them towards each other under the aerial without depreciating performance.

The 7 MHz Half-Square Vertical length ~33 to 38 feet • Spaced ~66'

Suspension Height ~ 36 to 40' • 50 Ohm feedpoint impedance

Can be directly fed at either corner or through parallel circuit at bottom

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To convert a 40 meter dipole into a half-bobtail, don't do anything to the feedpont connection. Just add 1/2 wavelength of wire to either of the legs. If you are not feeding your dipole through a balun, splic the extra wire to the leg that is connected to the center conductor of the coax after removing the end insulator. Slip the insulator back on and slide it down 1/4 wavelength (33' to 38'). You can secure the insulator by crimping the wire corner with a cable tie; if you twist it around the insulator, it will untwist when the array is tensioned. This insulator now serves as one of the corner supports. Attach another insulator to the end of the extra wire. This insulator serves as one of the end supports, with the feedpoint insulator serving as the other one. This completes the conversion of the dipole into a half-bobtail!

How to Convert a Dipole into a Half-Square

1/2 wavelength of wire is spliced onto a dipole. 

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You now have a DX antenna that looks like an inverted "U". The two vertical legs drop down until their end insulators hover 3 to 6 feet above the ground to which they are staked with bungie cords. The height of the aerial is between 36 to 40 feet. Right now we are testing it on 40 Meters at night. On February 12, 2018, the contraption worked into Europe until Noon (1100 UTC). Incredible for a piece of wire without any radials! 

Half-Square Working Europe Until Noon

February 12, 2018 • 7 Mhz

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Elevated Phased Verticals

PHASED VERTICALS
with Elevated Counterpoise

After 1 year, here's what we ended up with for the transmitting antenna.

East and West Verticals of the 7 MHz Phased Array • Construction Time: 4 Months • Cost: Under $200 (including radial wire)
Each vertical is elevated 4 meters above ground, and outfitted with 30 counterpoise wires. • The Christman phasing method is employed.

The 60 counterpoise wires are suspended from a catenary line strung around both verticals. • Counterpoise systems are insulated from each other.

Feedlines choked with W2AU ferrite-bead balun kits (Wireman $14).

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Schematic Diagram of 7.1 MHz Phased Verticals Using the Christman Phasing Method

Vertical length 34.5 feet • Spaced 34' 7" • 30 Elevated Counterpoise Wires per Vertical 36.5' • 84-degree RG-8X feedline 27.1' • 71-degree RG8X feedline 22.8' 

12 VDC automotive relay used in switching box. • Array beams towards vertical with delay line inserted in its feedline

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