Ground Radial Questions
Currently I am able to get on 80m - 10m with my full wave 40m loop and now I'm curious about 160m. I can tune in 160m for some SWL no problem, but I would like to be able to TX on it and since my full wave 40m loop is roughly a quarter wave on 160m it can potentially tune it in. At the moment I have a quarter wave radial cut for 80m that travels alongside the fence so its out of the way.
I have enough room if I continue to follow the fence all around my front yard for a quarter wave 160m ground radial, but that poses a tripping/snag hazard at the front gate. So here's my idea for a solution: I have a left over 10ft long & 2 inch diameter electrical conduit PVC pipe that I could helicaly coil the ground radial on to shorten up the overall length of the radial. Electrically it would still be a quarter wave on 160m and would be akin to something like a giant hamstick for a radial.
So my questions are: would this work? what should I expect from this kind of setup if it does?
I'm not sure I understand the relationship of the radials to the loop. Can you give us more details?
Any chance you can put up an inverted-L for 160? It's a great antenna, but you need radials. Check out the following two links for ideas. I'm sure others will add to this.
I'd add more details, but I have to get back to work here. :-)
It's been both my understanding and experience thus far that with a loop antenna if you're going to operate below the band it was cut for you need to have a RF ground of some kind and I opted for the radial. When I first tried to tune up 75/80m with my loop it wouldn't tune up and ended up getting the shack a little warm with RF. Putting the radial out solved that.
And no I can't get up an inverted L especially one for 160m. The most I can fit is a 1/2 wave dipole on 40m, but considering the circumstances I was lucky getting a full wave 40m loop up. With exception of where my loop is the house is surrounded by power lines being a 50x100ft corner lot in suburbia. So a large dipole or inverted L really couldn't be done. The loop was my best bet and so far its been extremely good to me.
1. Operating an antenna below its resonant frequency can be very hard on your equipment as it creates very high voltages which may short and damage your tuner. Wiser to build a bigger antenna!
2. wrapping whatever length of wire on a 10ft pipe is electrically equivalent to a tad more than 10ft. You can't fool Mr. Henry! The way to shorten an antenna physically is to add a loading coil.
3. Counterpoise and horizontal loops? Completely changing the resonant freq of a loop with a counterpoise HuH? This makes no sense.
I would suggest trying to get up a larger loop, so that it is closer in size to 160m. An inverted L loaded for 160m would be next easiest or whatever loaded vertical with the best radials you can manage.
There's just nothing like have a bottle of acreage stretcher, eh? Good luck! Bill.
I have had 4 different loops up only one now a 160m full size in a square at 48' and have never used a counterpoise with any all were coax fed. I have 3 antennas up that will cover 160 and only needs radials that is my Hy Gain HyTower that has a top mounted 160m kit / 1/4 wave radials for 10-160m the other is a OCFD 270' at 60'. My receive antenna is a beverage I hear better than I transmit only a kw.
73 de Fred N0AZZ
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A coil loaded dipole for 160 would be easier to use but choose your frequency brefore you design it. This will only work over a narrow part of the band !
Now I have a full sized dipole but before I moved out of the city I tried short wires with an ant. tuner but never had much luck on 160M.
I can operate from 1800 to 1830 without any tuner with my 250 ft dipole !.
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You can feed the loop as a single wire and it will basically accomplish the same thing as an inverted L. You are correct about the ground system though. For 160 I don't think a single radial is going to do the trick. I would opt for many shorter radials to lower the ground path impedance. The trick is that you will need to feed the loop like an end fed wire. This means the feed line also become part of the radiating antenna.
It wonk break any pile ups but it can work.
i'm sorry you don't have the experience or understanding to realize that others possess a skill set that you seem to dismiss as fantastical.
What he said.
I use a ladder line fed 400' dipole. have tried shorter things but you need radials, and the 'shorter things' should be treated as a single wire, add a coil to the loop, then add radials. You may want a relay eventually , if it works .....
"Clear intent is the best predictor of experience"
edit: just realized you aren't adding a vertical but using a ground radial with your loop. I've never heard of ground radials on a loop... (who knows, I just never heard of it...)
As far as radials, I don't think you can "load" a ground radial. Its about ground losses and return currents, not about impedance matching. You need the length in fractions of a wavelength... no loading coils.
Last edited by AE2CS; 11-16-2010 at 10:27 PM.
Just try to get in as much as you can. If you need to go around obstacles, bend the wire and go around it. The idea of ground radials is to make the ground AS CONSTANT AS POSSIBLE...that is to say, you don't want the ground resistance to change appreciably. Coiling up the wire won't help, but getting the length of wire in the ground will.
Bottom line: Short, long, bent, curved, is better than NOTHING. FYI: Ground radials for a loop need only be at least twice the loop diameter (if they're needed at all). A loop is self-resonant and the ground plays a minimal role (which is why they work so well so low to the ground).