Hello,
my self-built low-band QMX works fine with EFHW antenna on 40 and 20 meters. It usually switches on SWR protection on 80 meters.
I measured the actual SWR performance of the antenna at the connector in ham shack by VNa and got this:
80 m: SWR < 3 at frequencies above 3535, dip at 3684 (1.07)
40 m: SWR < 2 everywhere in the band, with a dip at 6844 (1.43)
20 m: SWR <1.8 under 14100, <2 in the whole band, dip at 13749 (1.36)
SWR protection seems to be working accordingly, except some glitches at 40 and 20 meters when it occasionally blocks TX without apparent reason.
However, I am shocked when see results of SWR sweep:
20M:
10 |.? ?***.? ? ?.***? ?.***? ? ? .? ? ? *|? **? .? ? ?*.? **50%*
? ?|.? ?*? *? ? ?*? ?*? .*? ? ?.? ? ?.*? ? ?.? ? ? *? ? ?*? **? .? ? ?*.? *? .
9.0|.. .*. * . . * . * .*. . . . . . .*. . ... . . * . . * * * ... . .*. .*. . .
? ?|.? ?*? *? ? ?*? ?*? *? ? ? .? ? ?. *? ? .? ? ? *? ? ?* * *? .? ? ?*.? *? .
8.0|.. * . .*. . * . .*.*. . . . . . . * . ... . . * . . |** * ... . .*. * . . .
? ?|.? *? ?.*? ?*.? ? **.? ? ? .? ? ?. *? ? .? ? ?*.? ? ?|** *? .? ? **. *? ?.
7.0|.. * . .*. .*. . .**.. . . . . . . .*. ... . .*. . . |*. .*... . * * * . . .
? ?|.? *? ?.*? ?*.? ? **.? ? ? .? ? ?.? *? ?.? ? ?*.? ? ?|*? ?* .? ? * * *? ?.
? ?|.? *? ?. *? *.? ? ? .? ? ? .? ? ?.? *? ?.? ? ?*.? ? ?|? ? * .? ? * * *? ?.
6.0|..*. . . * .*. . . ... . . . . . . . * ... . .*. . . | . .*... . * **. . . .
? ?|* *? ? . *? *.? ? ? .? ? ? .? ? ?.? ?*? .? ? ?*.? ? ?|? ? * .? ? * **? ? .
5.0|*.*. . . .** . . . ... . . . . . . . * ... . .*. . . | . .*... . * **. . . .
? ?|.*? ? ?.? ** .? ? ? .? ? ? .? ? ?.? ? * .? ? ?*.? ? ?|? ? * .? ?*? *? ? ?.
4.0|.* . . . . . . . . ... . . . . . . . . *.. . .*. . . | . .*... .*. . . . . .
? ?|.*? ? ?.? ? ?.? ? ? .? ? ? .? ? ?.? ? ?*.? ? * .? ? ?|? ? ?*.? ?*? .? ? ?.
? ?|.? ? ? .? ? ?.? ? ? .? ? ? .? ? ?.? ? ? *? ? * .? ? ?|? ? ?*.? *? ?.? ? ?.
3.0|.. . . . . . . . . ... . . . . . . . . ..* . * . . . | . . *.. * . . . . . .
? ?|.? ? ? .? ? ?.? ? ? .? ? ? .? ? ?.? ? ? . *? * .? ? ?|? ? ?*. *? ? .? ? ?.
2.0|.. . . . . . . . . ... . . . . . . . . ... **. . . . | . . .***. . . . . . .
? ?|.? ? ? .? ? ?.? ? ? .? ? ? .? ? ?.? ? ? .? ? ? .? ? ?|? ? ? .? ? ? .? ? ?.
1.0|.? ? ? .? ? ?.? ? ? .? ? ? .? ? ?.? ? ? .? ? ? .? ? ?|? ? ? .? ? ? .? ? ?.
? ? ----------------------------------------------------------------------------
? ? 6? ? ? 7? ? ?8? ? ? 9? ? ?10? ? 11? ? ?12? ? ?13? ? 14? ? ?15? ? ?16? ? 17
(shows SWR 8 at 14000 and then drops down in steep slope to something just under 3)
40M
10 |****? ?.? ? ? ? ? ? ?|? ? ? ? ? ?****? ? ?50%
? ?|? ? ? ? ? ?.? ? ? ? ? ? .? ? ? ? ?** .? ? ? ? ? ?* |? ? ? ? ? ?*. *
9.0| . . . . . . . . . . . ... . . . . * . . . . . .*.*| . . . . . *..*. . . . .
? ?|? ? ? ? ? ?.? ? ? ? ? ? .? ? ? ? ? ?*.? ? ? ? **? *|? ? ? ? ? ?*.? *
8.0| . . . . . . . . . . . ... . . . . .*. . . . * * .*| . . . . .*... * . . . .
? ?|? ? ? ? ? ?.? ? ? ? ? ? .? ? ? ? ? ?*.? ? ? ?*? ? ?*? ? ? ? ? * .? *
7.0| . . . . . . . . . . . ... . . . . .*. . . .*. . . |*. . . . .*... * . . . .
? ?|? ? ? ? ? ?.? ? ? ? ? ? .? ? ? ? ? ? *? ? ? *? ? ? |*? ? ? ? ?* .? ?*
? ?|? ? ? ? ? ?.? ? ? ? ? ? .? ? ? ? ? ? **? ? *? ? ? ?| *? ? ? ? * .? ?*
6.0| . . . . . . . . . . . ... . . . . . . * .*. . . . | **. . . .*... . * . .*.
? ?|? ? ? ? ? ?.? ? ? ? ? ? .? ? ? ? ? ? . * *? ? ? ? ?| * *? ? ?*? .? ? *** * *
5.0| . . . . . . . . . . . ... . . . . . . * * . . . . | . * . . * ... . . * * *
? ?|? ? ? ? ? ?.? ? ? ? ? ? .? ? ? ? ? ? .? *? ? ? ? ? |? ? *? ? *? .? ? ? ?*? *
4.0| . . . . . . . . . . . ... . . . . . . . . . . . . | . . * .*. ... . . .*. .
? ?|? ? ? ? ? ?.? ? ? ? ? ? .? ? ? ? ? ? .? ? ? ? ? ? ?|? ? ? ***? ?.? ? ? ?*
? ?|? ? ? ? ? ?.? ? ? ? ? ? .? ? ? ? ? ? .? ? ? ? ? ? ?|? ? ? ? ? ? .? ? ? ?*
3.0| . . . . . . . . . . . ... . . . . . . . . . . . . | . . . . . ... . . . . .
? ?|? ? ? ? ? ?.? ? ? ? ? ? .? ? ? ? ? ? .? ? ? ? ? ? ?|? ? ? ? ? ? .
2.0| . . . . . . . . . . . ... . . . . . . . . . . . . | . . . . . ... . . . . .
? ?|? ? ? ? ? ?.? ? ? ? ? ? .? ? ? ? ? ? .? ? ? ? ? ? ?|? ? ? ? ? ? .
1.0|? ? ? ? ? ?.? ? ? ? ? ? .? ? ? ? ? ? .? ? ? ? ? ? ?|? ? ? ? ? ? .
? ? ----------------------------------------------------------------------------
? ? ? ? ? ? ? ?4? ? ? ? ? ? 5? ? ? ? ? ? 6? ? ? ? ? ? ?7? ? ? ? ? ? 8
(roughly 7.5 at 7000 and drops in steep slope to about 3.8 near 7300)
80M sweep shows flat response at high SWR (10)
However, the most shocking result is shown with a dummy load: high SWR flat over all the frequencies...
What puzzles me is that SWR protection apparently detects the real SWR during regular transmit but "measures" absolute garbage in SWR sweep.
When transmitting into dummy load,
80m (3525 KHz): Power/SWR meter shows full power + some SWR (3 pixel bars) and activates SWR protection as I stop transmission.
60m (5355 KHz): practically the same as 80 meters?
40m (7025 KHz): SWR protection activated immediately, not TX at all
30m (10106 KHz): normal TX, power meter shows full power with some SWR slightly >1 (two pixel bars)
20m (14020 KHz): power meter shows nothing in teh power bar, 1 pixel bar in SWR indicator. Activates SWR protection after short time
What could be wrong? The PCB is quite packed so I am not sure where to start diagnostics. Maybe I should rewind SWR transformer?
73 Jindra
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