[TowerTalk] 80 meter quad loops
ersmar at comcast.net
Fri Nov 4 12:31:24 EST 2005
I believe this month's issue of QST (Nov) features a wire Yagi for 80M that uses coax on the outer elements to switch from director to reflector as required. A short length of coax is permanently connected to provide capacitive loading to make the element a (shorter) director; a second length of coax is switched in via relays to lengthen the stub to provide inductive loading to convert the element into a (longer) reflector. The DC lines to the two relay housings (large-ish PVC tubing and caps) are choked with torroids near the center coax feedpoint.
Sounds like what you need?
Gene Smar AD3F
> For the last few years I have been using four sets of rope supported quads..a
> two element facing JA, a two element facing VK, a two element facing SA, and
> a four element facing EU. All are tuned for the SSB part of the band.
> To operate CW contests, I lower the ends of the ropes supporting them screw
> in the extra pieces of wire, and raise them again. It's a pretty simple method
> but it doesn't solve the day to day excursions into the CW band.
> The loops are actually flattop delta loops so the pointed end faces toward
> the ground. The ends either have coax at the bottom or a rope at the bottom to
> keep it from blowing around.
> So what I would like to do is to put a relay and a coil at the bottom of each
> element to make the element resonant around 3725. They are currently
> resonant around 3775.
> Any idea of what kind of inductance would be required to make this happen? I
> know I would need to choke the relay wires. Would the old "coil it up"
> method work on the relay wires? Any special caveats on using this system?
> The system kicks butt on 80, but I would like the ability to switch back and
> forth between SSB and CW. Just using a tuner doesn't work, since the
> reflector isn't a very good reflector when you go down 250kHz. Any ideas?
> Bill K4XS
> See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless Weather
> Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any questions
> and ask for Sherman, W2FLA.
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