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I have a multiband SE-X80 HF vertical antenna which works ok from 20 meters to 10 meters with a tuner. It is attached to the railings of my apartment balcony at the moment. This is the antenna : https://www.thunderpole.co.uk/amateur-radio-homebase-antennas/se-hf-x80-vertical-hf-antenna.html

It is however mounted very close to the walls of the buildings. I am trying to get the antenna out further for a better radiation pattern and performance.

I found a way to attach a strong fiberglass tube extending out further from at an angle of 40 degrees from the apartment balcony. Would it be ok to attach the antenna to this fiberglass tube, or should the antenna mast be always metal? Thanks in advance.

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A fiberglass mast is perfectly acceptable. In fact it can be desirable, as fiberglass is not (usually) conductive whereas metal is, which means special care must be taken with metal masts to ensure they do not couple with the antenna in undesirable ways. A nonconductive mast on the other hand is effectively "not even there" as far as the antenna is concerned.

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  • $\begingroup$ Thanks for your reply $\endgroup$ Sep 14 at 16:59
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You're right to move it further from the building.

But in spite of what the website says, the antenna will definitely perform better if there's an RF ground or counterpoise available at its base. Usually whatever it's mounted to, will help with this, but if you mount its base on a fibreglass pole, it will have only the coax, it could result in RF in the shack, hot fingers when touching your equipment, and interference with the microphone, and even other electronics in the house.

To improve this I recommend:

  1. A counterpoise which could be as simple as three metal cables - one straight down, and two more at modest angles from this, either side of the pipe. Connected to the ground is good, especially if they're very short. You could also run one down the pipe, next to the coax, all the way to your ground stake if you have one. As it's an 80 m antenna, then the wires could be up to 20 metres long, less is probably fine.

  2. Properly grounding the coax as it enters the house, at a common ground that's connected to an earth stake, your mains / shack earth, etc.

  3. If you don't have a ground (second floor shack, etc) then put a common mode choke on the coax as it enters the house. For 40-10 m, if you're using thin coax like RF58, a simple coil of about 10 turns, 6 inches diameter, wound in a single direction would suffice. 80 m requires more. A few turns on an appropriate ferrite would also be fine, search this stack for other questions about baluns and chokes (but it's a deep rabbit hole).

sketch

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  • $\begingroup$ Sorry I've just realised you said Apartment. If you mean a multi-story block of "condos" then the wires will have to all come back to your balcony, which is OK. But you might need permission from the owner, an engineer to sign off on the mechanical design of anything hanging out, and let your insurance know that you've put it up, have permission, have engineering drawings. $\endgroup$
    – tomnexus
    Sep 14 at 19:50
  • $\begingroup$ "Perform better" is not definite! If the dropped counterpose is the same length as the antenna, then the feed point will then be at the middle of a vertical dipole, with a feed point impedance of around 75 Ohms at some frequencies. If that little box with the coax connector contains a 49:1 transformer/unun (to better match a highly off-center feed impedance), then the feed line will see into an impedance of under 2 Ohms. That usually causes a very high SWR. $\endgroup$
    – hotpaw2
    Sep 15 at 1:14
  • $\begingroup$ @hotpaw2 true, that configuration wouldn't work well. But it would work even worse without a counterpoise - the quarter-wave vertical doesn't become end-fed-half-wave just because there's no counterpoise. I suppose the whip has some R and L in it to make it behave better. It works at 80 m but it's only 20 m long, and it works at too many other bands. $\endgroup$
    – tomnexus
    Sep 15 at 6:58

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