I have installed a random (long) wire antenna at my house that is about 86' long and about 23' above the ground. I have the wire running direct to a Johnson Matchbox and then to the rig. It seems to receive quite well, but I am not able to tune the SWR as far down to 1:1 on 80 meters as I would like. While transmitting there is quite a large amount of RF in the shack. It will burn you. My parameters for the antenna are pretty limited. A center fed dipole is out of the question. What changes or adjustments could I make to improve the SWR on 80, more importantly the RF. Thanks, Peter.
Random (Long) Wire Antenna
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ka3jjz
Wiki Admin Emeritus
You didn't say anything about a good RF ground - everything I've read tells me that you would need to put in a bunch of radials, some for the highest band you want to work, some for the lowest (80 m). The RF in the shack and high SWR problems are often related. A single ground rod is not really a good RF ground unless you live in a swampy area...
If I had that kind of space, a Windom or maybe a G5RV would be my first choice. Our HF antennas wiki has links for these antennas - I think even the AC6V supersite would be a good place to go for this.
73s Mike
If I had that kind of space, a Windom or maybe a G5RV would be my first choice. Our HF antennas wiki has links for these antennas - I think even the AC6V supersite would be a good place to go for this.
73s Mike
jhooten
Member
Ground the matchbox to a good rf ground.
Use a lenght of old coax for the run from the matchbox to outside the shack. Tie the center conductor to the output of the tuner and hook the sheild to the the tuner ground. Outside tie the center conductor to the wire and leave the shield unconnected. Seal it good to keep water out.
Ground the Matchbox to a good RF ground.
86' is a little short for a long wire. Double it if you can. If not shorten it to about 65 feet and it will be a 1/4 wave on 80 and will still receive as well.
Ground the Matchbox to a good rf ground.
Use a lenght of old coax for the run from the matchbox to outside the shack. Tie the center conductor to the output of the tuner and hook the sheild to the the tuner ground. Outside tie the center conductor to the wire and leave the shield unconnected. Seal it good to keep water out.
Ground the Matchbox to a good RF ground.
86' is a little short for a long wire. Double it if you can. If not shorten it to about 65 feet and it will be a 1/4 wave on 80 and will still receive as well.
Ground the Matchbox to a good rf ground.
k9rzz
Member
Try a counterpoise for 80 meters. Cut 63 feet of wire (roughly 1/4 wave on 80 meters) and attatch it to the ground on your tuner, and lay it either outside on the ground or in your shack. I think you can loosely coil it up on the floor and it will work.
That's cured my RF in the shack.
If you want to go longer on the antenna, you can bend it. Try not to go more than 90 degrees if possible, but it will still work just fine. Dunno if that will help you or not, just a suggestion.
That's cured my RF in the shack.
If you want to go longer on the antenna, you can bend it. Try not to go more than 90 degrees if possible, but it will still work just fine. Dunno if that will help you or not, just a suggestion.
The antenna will have reciprocal current between the hot side and ground side and your tuner and radio are trying to be the other half of the antenna. Simply "grounding" the tuner to a ground rod will not satisfy the problem. The advise above to attach a tuned counterpoise wire is good and usually cures the problem. Just remember the counterpoise will radiate and also pick up noise from sources in your house, so route it accordingly. You could also try an "end fed zepp", which has a single antenna wire fed with balanced line and one side of the line is simply open. TV twinlead or 450 ohm ladder line will work for this but don't use coax!
prcguy
prcguy
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