The inverted V operation may be improved by moving the lower ends higher
and further from the operating position. A ground strap between the
tuner and the radio might help. Quarter wave of wire at 15 meters might
make an artificial RF ground at the radio if your ground wire from the
radio is long. Hook one end to the radio, run the rest around the room
with the other end open. MFJ makes a tuner box for getting more
frequencies out of a single wire.
The vertical will be a better DX antenna especially for transmitting
than the little inverted V, BUT it will hear noise and QRM from all
directions. Its already unbalanced so it needs no balun or unun at the
feed point. Its a little short for 40, long for the higher bands. On 10
m it will have poor low angle radiation. It will perform better on the
higher bands with resonant radials for each band which will also
decouple RF from the outside of the unbalanced feed line. That 20 feet
of vertical radiator is close to half wave resonant at 15 meters so will
be high impedance that can show up very low impedance at a quarter wave
a feed line away. 28 feet is pretty short for antenna to rig isolation
but more than 3/4 wave at 15 meters so the tuner should tune it OK.
Antenna that close to the rig may always have problems with RF in the
audio without extra attention to rig and microphone grounding.
73, Jerry, K0CQ
On 1/10/2011 5:52 PM, David wrote:
> Please bear with me for a few minutes while I explain the situation.
> When I purchased this house it had a 10 foot section of tower in the
> back yard with a basket ball hoop and back stop on it. I removed the
> basket ball stuff and installed 20 feet of fiberglass camo support
> poles and an inverted V with 23 foot long elements of wire. I also
> had a SGC 230 at the top of the pole to tune the antenna. Well the
> SGC has failed for the third time and I decided not to pay for the
> repair but to go with a manual tuner. So I talked to Stan at ten tec
> and got a used 238B . I then ran 300 ohm transmission line from the
> antenna to the tuner on my desk. Tune up at 20 watts no problem 10
> thru 40 meters. 40 meter SSB no problems. 20 and 17 had comments of
> RF in the audio at 100 watts from the Jupiter. 100 watts on 15 drove
> the Jupiter nuts with display blanking and shut down of the
> transmitter. So I am now plan to take down the V and replacing it
> with a vertical wire 19 feet long on t
>
> he fiber glass pole and 4 elevated radials just above the top of the
> tower section . Idea #1 is to run 15 feet of twin lead from the top
> of the tower/ base of the vertical to the house and a balun on the
> outside wall and 8 feet of coax to the tuner. Would a 1 to 1 or a 4
> to 1 ballun work better? Idea #2 is a 4 to 1 unun at the top of the
> tower and base of the vertical and 28 feet of coax to the tuner.
> Given the 30 foot total height restriction I have to live with I am
> thinking the vertical might be the better DX antenna. Comments
> please. _______________________________________________
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