What 3 kHz spacings rules. There never have been RULES about spacings on
amateur bands. 3 kHz works with 2.4 and 2.1 KHz filters (2.1 was the
standard Collins S-line filter, plenty good for communications, adding
unneeded highs with a 2.8 adds nothing to understanding). Adding highs
does nothing for THIN audio that already has excessive highs. Moving
your receiver BFO closer to the filter edge may add some lows to add
body, but won't add them if they aren't transmitted because the
transmitter filter was set with the BFO 300 Hz from the filter edge. A
wider filter will allow more QRM to be mixed with the desired signal
except on an otherwise empty band.
If you put a 2.8 filter in the 6.3 and keep the 2.4 in the 9 MHz IF, you
will accomplish only improving Inrad's bottom line without changing your
receiver's characteristics. They are always cascaded.
73, Jerry, K0CQ
--
Entire content copyright Dr. Gerald N. Johnson, electrical engineer.
Reproduction by permission only.
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