Advising needed for 14 mhz gp antenna

Thanks for that link, interesting stuff.

Hi, I just got started on SOTA and have been activating three summits in LA this summer. My antenna: A 1/4wave GP cut for 14060. Simple and cheap fishing rod pole, four radials, from appx. 1m above ground, sloping down to ground level, even just using rocks to hold the far ends. No balun, just a T-section, then coax straight to my transmitter. Used a VNA for the initial tuning/cutting at home, after that, no tuning at all.
Worked all europe this way, even the states. 42 QSO’s over three summits. Setup time once at the summit: appx. 10 minutes
Optimizing it, I thought about adding a balun and some tuning circuit allowing for 30/40m using the same wire, but realized I might just as well stick an Elecraft T1 tuner in the feed point and leave the hard work to it instead. Simple, lightweight, (almost) nothing to break.
Sure, I wont get as much power out on the low bands, but even with 2W and rundown batteries, I found myself battling with a pileup. :smile:

cheers and best SOTA
OZ1LQO

1 Like

Good Morning,

Let me precede this by saying that if your set up works for you then that’s what matters.

The 4 radial GP design ideally gives cno radiation off the radials and the pattern is circular in azimuth. The currents in opposing radials cancel each other out as far as the radiated field is concerned. Three radials may give a barely discernible cloverleaf pattern and minimization of radial radiation is easily destroyed if the angles are not 120 degrees. Two radials result in a slightly flattened circle with best results (lowest elevation angle and max signal) along the axis of the radials. One radial gives a match but what you have is a bent dipole with consequently bent radiation pattern and increased ground losses.

If you want to minimise ground losses and use on-ground radials use at least 20 radials of 0.2 wave length. However I certainly would put up with a few dB of loss to save the time in setting such a fine performing system up.

Does running out three radials take more time than setting up a dipole? I would say yes and they are a bigger tripping hazard, but the vertical doesn’t waste your signal on those pesky locals - it squirts it out to the horizon for the dx.

73
Ron

I remember seeing in “Technical Topics” a GP design with one radial which is bent back like a horizontal J, making an inverted T shape with half length radials. I keep intending to try it but have never got around to it.

Brian.

I reckon your vertical is about as close as you can get to optimal for a portable antenna.

My only comment would be to ensure the ends of your radials are well insulated from ground. They are a high voltage point and if you allow leakage to occur there will be losses and reduction in efficiency. I add a small length of light cord to each radial and use that to tie to a rock or a small tent peg into the ground where possible, allowing the end of the wire to be above ground (even by only 10cm) and insulated.

Ron’s suggestion that the vertical “cuts out locals” is not quite what I have experienced. I still work locals. After all, the radiation patterns of these single element antennas are very broad. The differences observed on charts are only a few db and we are not dealing with laser beams. However I agree 100% with the sense of his opening comment, if it works it is good and possibly even good enough!

73
Andrew
vk1da/vk2uh

Good point, elevating the radial ends above ground, I’ll keep that in mind :smile:

cheers/73