As mentioned in an earlier post, for the last few days I have been using the 15m earth-electrode and not the same antenna with the far end as a capacitive connection to ground as used previously. So far, I have spotted 14 unique stations (best DX DK7FC at 669km) and my own signal has been spotted so far by 10 unique stations (best DX F59706 at 570km) using WSPR.
Overall, my impression is the "proper" earth-electrode antenna is a few dB down, and more directional (?), compared with the similar arrangement but with the capacitive ground connection for the far electrode.
In the coming days I shall extend the baseline and repeat with the capacitive far ground connection. Based on results to date I would expect it to perform quite well, despite what theory might say.
10 Mar 2014
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4 comments:
Must have been quite a surprise to discover the coax coil Roger. I wonder how much coax and what diameter it was coiled into?
Alan G8LCO
No more than 3m length and the coil was not neat. My son must have wound the wire in (off the lawn) when I was hospitalised in September last year.
Well that's interesting, you would not think that such a short length of wire on the ground would give much coupling into the ground at LF or MF compaired with a rod driven into the ground. It has not quite been DRY !!!! so the coax jacket could have been in good contact with the ground surface but then the rod would not have been in parched soil either.
As Hams we tend to have ideal models of simple antennas hanging around in our heads yet here is something quite counter intuitive. Wire to rod would lead you to thinking of a lowish impedance at LF and HF, resistive losses being very dominant. Wire on ground at far end and you would think small series L , larger C and R and less current so the results seem to indicate something else is going on.
If we assume that at these frequencies the horizontal wire and ground return currents do not produce useful radiation then we are left with two vertical radiators at each end of the wire with a small phase shift from the loading which would conventionally give a figure of 8 pattern. Perhaps the currents into the ground are influenced by utility conductors however given the wavelength it would seem that the radiation should still be 8 shaped.
Well Roger you did say that you were running out of experiments, seems that you might have a new seam revealed in your back garden! The feedpoint Z would be interesting as would wspr'ing alternately with both wire terms but that would need swapping matching as well. ( that would give very good polar diagram data as conditions would not change very much between cycles).
Alan G8LCO
Alan, I was surprised by the results with the "earlier" 15m spaced earth-electrodes which had the far electrode not well grounded.
Indeed I am running out of experiments to do without climbing ladders,which is beyond me until I am fitter again (stroke impairments),which could be many months in the future.
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