Earth Strap

Submitted: Monday, May 07, 2007 at 07:29

ThreadID: 45164 Views:3717 Replies:2 FollowUps:6

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blue one

Is it worth while to fit an earth strap to the car ( Car to ground) to improve the performance of a HF radio?

Cheers

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Reply By: Mike Harding - Monday, May 07, 2007 at 08:17

Reply By: Tony Middleditch - Monday, May 07, 2007 at 13:58

Monday, May 07, 2007 at 13:58

No. Instead, use a counterpoise. This is a 1/4 wavelength bit of wire (size not important) that would connect to earth at the base of the antenna and simply sit on the ground.
Multiple counter poise wires used around the antenna will in effect be radials. They will markedly increase the amount of RF that actually radiates from the antenna rather than heat up the ground. Short vertical antennas an HF are very inefficient.
Cheers, Tony.

AnswerID: 238388

Follow Up By: Member - Roachie (SA) - Monday, May 07, 2007 at 14:34

Monday, May 07, 2007 at 14:34

I still reckon he's talking about an anti-static strap (car to ground)....One of those rubber straps that hangs down and drags along the road/ground etc.

But; I wouldn't put money on it......It's just the way he's phrased the question (twice now, in fact.....2 separate posts)

FollowupID: 499479

Follow Up By: Mike Harding - Monday, May 07, 2007 at 14:58

Monday, May 07, 2007 at 14:58

Tony:

Having recently completed an experiment trying to use counterpoise lines (which only simulate ground anyway) to perform _exactly_ this task with a vertical antenna for use on 80m and 40m I found I needed at least 12 of them before I started to get a noticeable difference in Rx or Tx signal. My experience concurs closely to that detailed in the ARRL Antenna Book - I seriously doubt one would be any use at all.

Mike Harding

FollowupID: 499483

Follow Up By: Tony Middleditch - Monday, May 07, 2007 at 15:39

Monday, May 07, 2007 at 15:39

Mike, the main purpose of using one counterpoise is as an artificial earth. The advantage of using them over a "real" earth is when experiencing RF feedback type problems.
I found that when I switched from coax to open wire feedline for the wire antenna, that the only way to kill stray RF was to use counterpoises.
I got a decent zap off the CW key! I use 2 wires of slightly different lengths per band. Also, I still use an earth "mat" system under the floor consisting of heaps or copper radials originating from the main earth rod and chicken wire clamped together.
The idea of the mat is to try and have an effective earth to work against when strapping the feeders together thus making the antenna a top loaded vertical.

The main earth rod is under the floor, directly under the antenna tuner.

Mike you may be interested in the present HF wire antenna. It uses home made open wire feeder - estimated to be 600 ohms into a full wave horizontal (sort of) delta loop that is resonant on 40 metres. Works a treat on 30 & 40 with a significant reduction in noise pick up. It does tune on all bands. Performance on 80 has not been fully tested but RX reports would have it down as compared with the 80 metre flat top zepp.
Cheers, Tony

FollowupID: 499490