If you take the "250 Hz" marketing name of the filter too seriously and
set it to switch in at a DSP bandwidth of 250 Hz, then yes, it is
perhaps too narrow for comfortable use with RTTY. On the other hand, if
you set the filter to switch in at 350 Hz, the combination of the "250
Hz" filter with a 350 Hz DSP bandwidth seems to work quite well for RTTY
when QRM is heavy. When QRM is not quite so bad, you may get better
decoding results using wider bandwidths in both the roofing filter and
the DSP.
73,
Rich VE3KI
W0EB wrote:
The narrowest filter I have in both receivers is the 400 Hz one. I
borrowed a K3 that had a 250 Hz filter in it once and tried it on RTTY.
It works, but it's right on the margin of being too narrow. If someone
is using one of the older Packet TNC's that have RTTY mode in them (they
used 200 Hz shift instead of 170 and there are still a lot of them out
there) it's really hard to get them tuned in with a 250 Hz filter,
especially in weak signal/selective QSB situations. The 400 Hz filter
doesn't seem to have that limitation though it does let slightly more
noise in (easily handled with the DSP filters anyway.
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