''directionality along the line of the earth-electrode baseline and a null
off the sides''
A terminated travelling wave 'thing'ey'
then ! sort of makes sense , the Amps in
the top section are maximised by the
diffused return path , may be not
cancelling ?
73 -G..
This evening I've been noting my WSPR S/N reports from stations across the
country and nearer Europe using my 9m long Marconi antenna (an average
arrangement for a small garden plot like mine - but not the best) and comparing
these with the reports last night when I was using just the 15m baseline
earth-electrode "antenna". I crudely plotted the "improvement factor" in dB on a
polar plot. Each dot represents a station reporting my signal with the dB
improvement over the earth-electrode antenna plotted on a 0-20dB scale out from
the centre. This is not good science, it is G3XBM science I'm afraid, but it
give a fair idea of the difference and how direction affects this (see attached
rough polar plot).
Although in some directions the difference is very
little, in other directions the reports are up to 14dB better on the
(omni-directional) Marconi.
My conclusion is that the earth electrode
antenna is behaving somewhat like a loop with some directionality along
the line of the earth-electrode baseline and a null off the sides. With stations
receiving me off the sides there is most improvement with the Marconi, and less
difference with stations end-on who were getting a reasonable signal with the
earth-electrode antenna.
CONCLUSION: the simple, stealth,
earth-electrode antenna is a VERY useful antenna on 472kHz as long as one is
prepared to accept a 2-14dB loss compared with a "small garden" Marconi. In
all honesty, I am getting better reports on the Marconi but few new stations are
copying me: most could copy me on the earth electrode antenna.
I
shall run WSPR overnight to see if any more distant stations copy me, then
probably put away the 472kHz gear and Marconi for a while to find another
interesting challenge - possibly something on 10m or VHF.
These last few
days have been fun, and that is really what this hobby is about.
73s
Roger G3XBM
