I had read, of course that there was a blow-by issue with the 920's, but
when I found a good deal on one I went ahead anyway. For the 2005 CW Field
Day I installed an Inrad 400 Hz CW filter and together with the DSP that
did, as reports said it should, quite a good job.
Recently, I measured the selectivity of my 920's filters and the ultimate
rejection really is poor.
400 Hz filter:
+/-KHz dB
0 0
0.31 -3
0.44 -6
0.49 -10
0.59 -20
0.64 -40
1.56 -50
2.00 -60
The CW filter skirts get a lot wider after 40 dB down and though I couldn't
get below 60 dB down with my signal source, it looks like after that rolls
off only at about 9 or 10 dB per KHz. Put another way, coupling _around_
the CW filter looks like it's only about 34 dB down.
Has anyone on the list modified their 920 to improve this? I have in mind
filter control-line bypassing. and strategic application of copper tape in
the filter area. Or do I have to spend the money for an Inrad Switchboard?
FWIW, I checked the SSB filter too:
+/- KHz dB
0 0
2.3 -3
2.6 -6
2.7 -10
3.0 -20
3.7 -40
4.1 -50
5.4 -60
Cortland
KA5S
_______________________________________________
Yaesu mailing list
Yaesu@contesting.com
http://lists.contesting.com/mailman/listinfo/yaesu
|