Counterpoise tests - elevated 3 ft. vs. on ground
17 foot counterpoise wire, radio on TV tray table about 28 inches high.
Counterpoise wire connected to DC charging jack 'outside' negative terminal.
Two fiberglass driveway marker poles, with a small wire hook at the top, about 3 ft. above ground.
One pole about 9 feet from radio, 2nd pole 17 feet away.
Tests with full length counterpoise, and with wire doubled back to closer pole.? So counterpoise lengths measured about 9 ft. and 17 ft.
Tested with GRA-1899 antenna, on 20 and 40 meters.
20 Meter tests, resonance and SWR:
9 ft, elevated -??? 17 ft elevated
13.720 mHz, 1.2:1??? 13.730, 1.0:1
9 ft, on ground??? ??? 17 ft, on ground
13.680 mHz, 1.3??? ??? 15.200 mHz, 3.6:1
40 meters:
9 ft, elevated??? ??? 17 ft, elevated
7.200 mHz, 1.0:1??? 7.200 mHz, 1.0:1
9 ft, on ground??? ??? 17 ft, on ground
7.080 mHz, 1.0:1??? 7.080 mHz, 1.0:1
In summary, I found much, much less variation between elevated and on ground counterpoise than I had expected from lots of research on-line and in books and magazines. At least on 40 meters.
Testing was done in my yard, with fairly dry, sandy soil with minimal grass and in an area of relatively low ground conductivity (as mapped by the FCC).
Now, a few days too late, I realize that I should have also measured with the counterpoise disconnected!? However, when I've 'informally' checked other times, the difference between with and without counterpoise was large.? It was often hard to find any resonance at all.
I've gotten off to a slow start on another project, too - an end-fed half wave antenna.? That will be in a new subject thread, when there's anything to report.? So far, it's just winding a matching transformer.? Next may be finding a simple way to get the far end of the wire up into a tree, in a way that's simple to get it back down again.? I've used the slingshot method, and also a 'pistol crossbow', to get wires over tree branches.? The portable EFHW wire needs to be easily retrievable, though.
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Doug, K8RFT
