[TenTec] Crystal vs. DSP Filtering

[Bill Tippett]

Hi John,

	There are two distinct schools of thought on this,
nicely summarized here by SM5BSZ (he developed the
Linrad DSP program used by many EME guys):

http://antennspecialisten.se/~sm5bsz/weakcom.htm

	There could be two issues involved, one is hardware,
i.e are your filters are all working correctly, the other
is psychoacoustic, which has to do with how your
brain's DSP works (as stated above some people prefer
wide bandwidths while others prefer narrow bandwidths).

	I've generally never liked extremely narrow filters for
weak signals, because of ringing problems.  However,
Orion's 110 Hz DSP is very friendly to my ears and I find I
use it fairly frequently for very weak signals.  Of course
this make no sense in a contest where stations may call
you +/- 500 Hz from your transmit frequency.

	In your case, you might want to verify the actual
bandwidths of your filters and also check their insertion
loss.  This is fairly easy to do with the receiver itself if
you have a stable (frequency and amplitude) signal
generator.  You can simply watch your S-meter as you
change filter BW's to see if you have any unusually
large insertion losses.  You can also use your receiver's
6 dB attenuator as a reference to check the 6 dB filter
bandwidths (tune each side of the sig gen and note the
point where the signal drops 6 dB on each side).

				73,  Bill  W4ZV