Wire Antennas and Foliage

[VK2CSW]

Hi All,

Although I live on a large block with a couple of generous sheds, there are no big trees closer than 40 or 50 metres from the shed. To complicate things that 40 or 50 metres also crosses the compacted earth driveway to the sheds (i.e. no chance of digging a trench).

Behind the shed, is a boundary fence and in between is a row of four or five metre tall Callistemons (aka Bottle Brushes).

I was toying with hanging a 40m EFHW in the Callistemons.

Is contact between the wire and the foliage an issue?

Same question for an OCF or dipole.

Cheers

[VK3PY]

Hi Colin,

Contact between the wire and foliage will very likely be an issue on those bands where it occurs in the vicinity of a high impedance point. For example, I once erected a 40m EFHWA by simply slinging it over a tree branch, forming a shallow inverted-V shape, where the apex was close to the wire's centre. It worked fine on 40m, but not on 20m. Even though the wire was insulated (PVC), there was sufficient capacitive coupling to the branch to de-tune it on 20m, where the apex happened to be a high-impedance point.

Some tree pruning might be advisable.

73,
Chas
VK3PY

[VK2CSW]

I am not sure pruning would be helpful, as then there would be no longer be much support

Callistemons are not substantial trees, on the whole. I suppose it wont take a lot to give it a go, once the toroids and capacitors for the 49:1 balun turn up.

Actually, as I type I realise that there is a 20m dipole I built for some portable work that is languishing in a crate. Maybe I could press that into service as an experimental antenna...

[VK5TM]

The other thing to remember is that when it finally gets around to raining, wet foliage will have a marked effect on the antenna performance.

[VK2CSW]

The other thing to remember is that when it finally gets around to raining, wet foliage will have a marked effect on the antenna performance.

A) It doesn't rain here - well comparatively
B) If it is raining, it's a metal shed so an unpleasant place to sit and listen to radios...