To: | "[email protected]" <[email protected]>, [email protected] |
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Subject: | LF: Comparing earth-electrode v. Marconi antenna on 472kHz |
From: | Roger Lapthorn <[email protected]> |
Date: | Tue, 8 Jan 2013 21:06:02 +0000 |
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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).
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. 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. These last few days have been fun, and that is really what this hobby is about. 73s Roger G3XBM
polar.jpg |
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