Re: Antenna Isolator install


Chris Moulding
 

I've just got back from holiday so I can answer questions more easily rather than relying on a very dodgy internet connection.

Answers to recent questions...

1) Can it be used with a 40m vertical?

Yes. The vertical antenna in the article is a G7FEK multiband vertical with a 1/4 wave section for 40m.

2) Is there and advantage in adding more loops?

Yes, I only had two loops to test the idea at both home and workshop locations. I tried an extra overlapping loop to prove that it improved performance.

3) I already have 32 buried radials...

Try connecting the ends of adjacent radials together to reduce the capacitive coupling to nearby electrical wiring.

4) A vertical antenna is noisy!

From the work I've done over many years I've proved that it's not the vertical element that picks up local RF noise, it's the capacitive coupling from the ends of the radials or straight counterpoises even if they are buried.

Unless you live on seawater or a saltwater swamp the ground has a relatively high resistance and RF at HF will penetrate several metres into the ground. The Beverage antenna uses this fact and that the speed of the wavefront is different in air and in ground. The wavefront starts to slope at the air/ground junction (surface of the ground). This allows a vertically polarised wave to couple to a horizontal wire.

Laying a horizontal wire on the ground forms a version of the Beverage antenna (Beverage on the Ground). This has slightly higher loss than the typical Beverage antenna mounted 1 or 2m above ground but still forms an excellent directional low noise HF antenna.

Laying radials and coax in the ground unless they are several metres deep or in saltwater does not shield the antenna from noise as much as would be expected or hoped.

If anyone wants to study this in greater detail I've collected all Harold Beverage's articles and patents from 1921 to 1923 and have links to them from a web page of some work on Beverage antennas I did two years ago:

http://www.crosscountrywireless.net/beverage_antenna_amplifier.htm

Regards,

Chris


Regards,

Chris

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