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Author Topic: Vertical interaction with fence ??  (Read 1116 times)

Posts: 27

« on: June 11, 2005, 12:24:58 AM »

Dear Elmers,
For now all I can do antenna wise is a vertical pole
A: 7m Steel scafold pole and 3m fibreglass whip ontop
B: 10 - 12m "Bought-in" telescopic fibreglass pole
Both with an insulated flexweave wire to the top as a radiator, fed at ground level with SGC 239 coupler and several 10-12m radials evenly spaced.

This HAS to be mounted to a fence post that supports a  1 m high chainlink fence (thus the scacfold pole will touch the fence or if rapped for insulation not touch but be only the insulation thickness away from the fence and some coupling will take place hence the fact I though of using the insulated wire on the farside and not the pole at all as radiator. The wire will however couple with the fence AND either pole.
Question 1. How severe might it affect the antenna as I cannot guarantee the fence is not grounded, probably is as it runs away from my property some 500m in both directions?
2. Should I add the fence to the "ground radial system"?
3. Should I keep the "radiator wire" some foot or two away from the pole to say 1.5m high to clear the fence height?
4. Being a vertical I modelled it in enzec And high current is present in this antenna at and immediately above the feedpoint, has this any bearing on the coupling "magnitude"?  I have only the evaluation copy which allow 20 segments only so modeling the fence was, lets say, a challenge and it looks like it slaughters the radiation pattern, especially 20m and up, BUT how acurate is my model with only 15 segs used to model a chainlink fence(closely woven I might add).

I did look through verticals in elmers and googled it but all thats clear it will affect it and does not clarify my above questions, Sooo, please help??

Bottom line, am I wasting my time and have real danger of TVI (BAD BAD neighbours, they are going to move so in 3 months I can do something better) OR would it be better to use (buy) a Buddipole or suchlike (This will also be only 2m away from the same fence!)but above.

Thank you in advance, sorry about the lenght but I tried to give the picture for fear of misconceptions.
Etienne Swanepoel 2E0ESW

Posts: 27

« Reply #1 on: June 11, 2005, 12:28:16 AM »

Sorry , forgot to say I am attempting an "all Band" HF antenna 80 - 10M
Etienne Swanepoel 2E0ESw

Posts: 85


« Reply #2 on: June 11, 2005, 02:02:55 AM »

The fence, grounded or not, will function as a counterpoise... use it! As with any vertical, the more radials under it the better, so if you can add them, do so.

Mount your tuner to one of the fence posts and your antenna mast above that. As your feed point will be several inches from the fence and only run near the fence for a few feet, simply keep the wire away from it several inches. The biggest concern with the feedpoint will be safety. Be sure it is insulated to prevent anyone from coming in contact with it.

Few of us have the perfect antenna farm. Few antennas are installed in lab conditions and perfom well. Use what you have.

To keep the feedline from radiating, which it shouldn't, at the input of the tuner you can add several turns of coax (approx 20cm inner diameter) to act as a choke.
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