Dick,
If your filters are adjusted correctly (best done using Spectrogram, as
others have mentioned), it may be that you're not tuning the CW signal to the
center of the filter's band pass (usually set to 600Hz). I recently added a CW
tuning indicator to my K2, and now, once the indicator shows that the CW signal
is centered at 600HZ, I can switch to any of the much narrower XTAL or DSP
filters and the signal is always right there. To avoid the slight reduction in
signal level with the narrowest XTAL filters, I have my narrowest XTAL filter
set to 300Hz and when needed, then use my narrowest DSP filter, which is set to
100Hz.
73,
Bob W1SRB
-----Original Message-----
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED] Behalf Of Lemkes
Sent: Friday, August 11, 2006 10:58 PM
To: [email protected]
Subject: [Elecraft] K2 Noise Blanker Slot as Additional IF Amplifier
Stage
Has anyone thought of, or tried modifying the K2 Noise Blanker to be an
additional K2 IF amplifier stage?
My problem is that when I really, really need the crystal filter, I am
trying to copy a very weak (but readable) CW signal with adjacent S-9 QRM.
When I switch in tighter than about 1200 Hz of crystal filtering, I tend to
lose the target signal due to filter loss. ( Losing the target signal is not
because the BFOs are not properly calibrated).
When I use just the DSP filter to block the adjacent S-9 QRM, then I still
lose the target DX due to AGC "pumping" (without the IF "roofing" filter).
I'd really like some additional IF gain to compensate for the crystal filter
loss.
I would try using the Noise Blanker's U1, MC1350, as the added IF stage,
and use U3, the Controller's decoded program lines to adjust U1's AGC input
for front panel gain control. I could use P1's pin 8, 8R, as power for the
MC1350 so that it's only active on "receive".
Any feedback would be appreciated.
73, Dick, AD7AF
Dick and Marty Lemke
PO Box 1038
Ocean Park, WA 98640
Tel. 360-665-2438
www.lemkestudios.com
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