First, thanks to the many nice hams who responded to my posting on this, both
on and off list.
Secondly, my apologies for having seemed to "hit and run" with this topic. I
was out of town over the weekend for a conference.
Steve, N4LQ, observed that there seems to be a lot of variation in individual
filter loss characteristics. Bill, W4ZV shared test data from George, W2VJN,
on a 221 filter. The data indicates there is also some variation in center
frequency that can contribute to additional rolloff loss when the roofing
filter is mismatched to the downstream 9 MHz IF filter. George also pointed
out there are limits (as far as low pitch CW reception goes) in the Omni VI due
to low end rolloff in the 2.4 KHz filter that is in the 9 MHz line.
On the new INRAD reflector, George is soliciting comments concerning a CW
roofing filter (for the Omni VI series) with 500 Hz offset. I would encourage
those who have expressed an interest in such a filter (and even placed orders)
should perhaps join the INRAD reflector and make their thoughts known:
http://mail.inrad.net/mailman/listinfo/list_inrad.net I still feel the 500 Hz
offset roofer is worth pursuing, based on my positive experience with the INRAD
753 filter. I suggested that George consider offering a 400 Hz BW filter with
500 Hz offset (essentially, a "tweaked" 753 filter). I also suggested that a
compromise might be to set the roofer at 600 Hz offset to match the 753.
George wants to know how to proceed here, so others with strong feelings may
wish to jump in with their oar!
73, Chuck NI0C
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