[MRCA] Vertical Antenna Relay Project

[W2HX]

Thanks, Ray. Those contactors are very cool.  Mine are not motorized, they are simply large solenoids. So far I have about 17 radials installed between 20 and 60 feet due to property edge limitations.  The majority of the radials are probably 40 feet.  In the spring I will try to add some more. I have no idea how this will perform, but time will tell.

73 Eugene W2HX

From: Ray Fantini [mailto:RAFANTINI at salisbury.edu]
Sent: Monday, November 17, 2014 10:18 AM
To: W2HX; mrca at mailman.qth.net
Subject: RE: Vertical Antenna Relay Project

Nice looking project. The contactors you used look a lot like ones that I have seen used in broadcast service for selection of different phase networks and ATU systems for day and night patterns in AM, and would speculate that they are good for at least a Kw without any issue. I have rebuilt quite a number of Harris Broadcast contactors that are used for selection of different tuning networks for a couple 5 Kw AM stations that I take care of in my spare time, did a video of them on YouTube at:

http://www.youtube.com/watch?v=NP6SL_gUbus

How many ground radials did you install? And how long?

Ray F/KA3EKH

From: MRCA [mailto:mrca-bounces at mailman.qth.net] On Behalf Of W2HX
Sent: Saturday, November 15, 2014 4:52 PM
To: mrca at mailman.qth.net<mailto:mrca at mailman.qth.net>
Subject: [MRCA] Vertical Antenna Relay Project

Hello friends,

I've been feeling inadequate lately. K4CHE always showing some great homebrew projects and I haven't done much. So here is a project I've been working on.  I've been working on installing a 43' vertical antenna and radial system for some DX work. And just to have an alternative antenna to a wire thrown out the window or a non-functioning dipole over the house.  In my shack, I have some radios that do 100W, 400W and 1000W. The trick was how to couple various radios to this vertical. So I settled on using two different antenna couplers. One is a Harris RF-382A 500W coupler, the other is a Sunair GCU-1935 1KW coupler.  The Harris normally must interface to a Harris radios to receive the correct control signals. However a smart fellow on the Harris list has made a small circuit board to automatically control the coupler with just the presence of RF (and some supply voltage). This allows the coupler to be used with any radio, pretty much. Change frequencies, give a whistle, watch your SWR and you're good to go.    The Sunair is more complex, although I believe I can also make a box in the shack to remotely control this coupler. I have run 12 conductors already to the antenna site to control this coupler.

Even though the Sunair could theoretically handle both high and low power, the Sunair will be a big project in itself whereas the Harris is ready to go. Maybe in the spring I'll get the Sunair operational for some higher power work (I think our sunspots are on the outs for a while).

So the project is how to switch between these two couplers? In addition, when the system is not in use, I want to ground the 43' vertical.  Here is how I did it. I found a pair of large, HV relays at Fair Radio. These have a 1.5" gap to isolate the positions. Here is a drawing of my idea of how this will work. One relay connects the antenna either to GROUND or to the other relay. The other relay selects between Coupler 1 and Coupler 2.  Here is the diagram:

http://www.w2hx.com/x/Antenna-related/Vertical/Antenna-Relay-Box.jpg

The control lines will go into the shack to run the two relays independently.  So after planning and an order to McMaster-Carr and finding some time to work on this, here are the results:
The inside.  The white wire is 50KV wire and handles the RF connections from the insulators to the relays and out to the vertical:  http://www.w2hx.com/x/Antenna-related/Vertical/IMG_5988.JPG

Here is the bottom, you can see a #6 cable on the left for ground and the blue control lines on the right: http://www.w2hx.com/x/Antenna-related/Vertical/IMG_5989.JPG

On the side the insulator on the left goes to the antenna and the insulator on the right goes to coupler 2: http://www.w2hx.com/x/Antenna-related/Vertical/IMG_5990.JPG
On the top the insulator goes to coupler 1 : http://www.w2hx.com/x/Antenna-related/Vertical/IMG_5992.JPG

Here I have outlined the RF path when coupler 1 is in use and the grounding relay is in the "operate" position (see red line):  http://www.w2hx.com/x/Antenna-related/Vertical/Coupler%201.jpg
And when coupler 2 is selected: http://www.w2hx.com/x/Antenna-related/Vertical/Coupler%202.jpg
And finally when the antenna is grounded. http://www.w2hx.com/x/Antenna-related/Vertical/Antenna%20Grounded.jpg

Here are some videos of the relays operating:
Coupler select relay: http://www.w2hx.com/x/Antenna-related/Vertical/VID_20141114_184756_594.mp4.mov
Grounding Relay: http://www.w2hx.com/x/Antenna-related/Vertical/VID_20141114_184807_697.mp4.mov

And here is the vertical itself where all this magic will take place.
http://www.w2hx.com/x/Antenna-related/Vertical/final2.jpg

The last thing I need to do on this part of the project is some snubber diodes across the relay coils. And that is phase one of this project. Phase two is another enclosure that will do some other things. Stay tuned (pun intended)!


73 Eugene W2HX

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