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My garden has, at one end, a wall of large (chest freezer size) randomly placed granite boulders loosely filled with earth and stones.

Currently my vertical is in the garden about 10m east of the bank.

I could mount it up on the bank, putting it 2 metres above the garden and surrounding fields and with, subjectively at least, a much better "take off"

Should I move it?

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  • $\begingroup$ well, I might be missing something, but apart from the effort, cost and potentially longer feed line and thus increased losses, is there anything you foresee that could be worse about the more elevated position? We don't know your garden's topology as well as as you do, so you'd be the first person I'd ask. $\endgroup$
    – Marcus Müller
    Commented May 23, 2023 at 22:26
  • $\begingroup$ Guess I was concerned about the poor ground the dry boulders would present compared with good moist garden soil. $\endgroup$
    – quanglewangle
    Commented May 24, 2023 at 1:57
  • $\begingroup$ @quanglewangle Your question lacks details: What type of antenna is it? What band(s) is this antenna used on? Is the antenna ground mounted or on a mast? Are you using radials currently and would those radials be transferable to the embankment in the same arrangement? If everything is working currently, Marcus Müller's point about feed-line loss is probably the best reason for not moving the antenna to gain some minute fraction of a wavelength in altitude. $\endgroup$
    – Louis Seaman
    Commented May 24, 2023 at 10:45
  • $\begingroup$ I have 10m,15m,17m and 20m fan vertical. 16 on-surface radials of lengths varying from 2m - 10m. No more feed line needed since there is enough spare on the current Rg213 loosely coiled outside shack. Would gain about 3m height and the bank wouldn't be in to way going west. Bank is big enough to accommodate current radials. $\endgroup$
    – quanglewangle
    Commented May 24, 2023 at 12:17

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quanglewangle, so you have a 1/4 wave ground-mounted monopole antenna in a multi-band fan configuration with ground-mounted counterpoises for each band (presumably).

I would say all other things being equal, the only band where adding the height of the berm might be marginally noticeable, is 10M, since 3M of height is ~1/4 wavelength; the other bands will likely not see any difference due to the increased altitude and potential of "blocking" your radio wave.

The thing that might help by being on the berm, is not having a "good Earth ground", and therefore reducing ground losses, in other words, not having your radiator too close to Earth, but again, this may only make a difference on 10M. Also, I'm not suggesting you don't ground your antenna's counterpoise, but I've read that in the USA, single-point grounding to your home's utility ground, via an independent conductor, is the proper way to ground for lightning protection, but not RF purposes; however, if your coax is on the ground anyway, you may already have fairly good elimination of stray RF on the coax shield, through capacitive coupling with the Earth.

One other side-note, since your counterpoise elements are 90 degrees from your radiator, this should mean that your input impedance at your resonant frequency on each band is ~37 Ohms, which means your best VSWR on each band is 1.5:1, and when you're operating away from your resonant frequency, your VSWR will only get worse. I might suggest a 1.5:1 UnUn if that is your "best" VSWR, whether or not you move the antenna. This guy on eBay https://www.ebay.com/usr/hifi1200 has had 1.5:1 UnUns in the past that I have purchased and found were excellent quality, he currently doesn't list any now, but you might try contacting him if you can't find one anywhere else.

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    $\begingroup$ Thanks for very comprehensive response Louis Seaman. I like the idea of a 1.5:1 unun - presumably it is used "back to front" since their primary use is to go from 50 to 75 Ohm? $\endgroup$
    – quanglewangle
    Commented May 25, 2023 at 6:21
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    $\begingroup$ As a matter of fact, the UnUn is designed for your application, but yes, otherwise it has perfect reciprocity. When I bought it, I wanted it for a dipole which had an impedance of ~73 Ohms, so I was using it "backwards"; the issue with that is that it's wired as an UnUn and meant to have one of the elements remain "ground", and for a 1/2 wave dipole to actually perform as such, it requires differential voltages on each 1/4 wave element, otherwise it's no better than connecting the shield of a coax to one leg, and the center conductor to the other leg; so in short, I connected it differently. $\endgroup$
    – Louis Seaman
    Commented May 25, 2023 at 10:36

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