I just installed a new Bencher YA-1 and it seems to have a strange effect.
The resonant point on 20m shifts downward by about 100 kHz. When I take the
filter out of the line the SWR is back to normal (I keep a spreadsheet of
measurements under various weather conditions). Also, with the filter the
minimum SWR value seems to be a tad higher.
I measured the filter with an MFJ 259 and a dummy load, and the SWR is 1:1
up to about 26 MHz, then 1.1/1.2:1 up to the cutoff frequency. So the
filter itself seems to be ok. Is it possible that I have some kind of
interaction between the filter and the antenna (A3S at 13', about 100'
RG-213, choke balun)? The lowering of the optimum SWR frequency when the
filter is in the antenna line is the same between the MFJ-259, 100W and
1kW. Always lower than my "normal" curves and back to normal when the
filter is removed.
Should I bring the filter back and try another one? Has anyone else
observed this?
BTW: the "old" filter (a used YA-1) had arced over a few weeks ago. It had
worked fine up to then. When I drilled out the rivets, I found what looked
like a solder ball next to one of the capacitor disks, right where the
arcing occurred. Upon Bencher's request I returned the (out-of-warranty)
filter, but haven't received their analysis yet. That filter didn't seem to
have this effect, but now I'm not sure. Since I bought the new filter
today, I wouldn't hesitate to return it under warranty if the observed
effect is not normal behavior.
Michael, K1JE
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