w2bvh wrote:
According to the wsjt manual FSK441 uses 882, 1323 1764 and 2205 Hz
tones in its encoding. My K2's OPT1 filter has the 2205 Hz tone on
the IF filters shoulder. By eye its about 3-4 db below the passband.
(In a
If it uses those frequencies, and conforms to the licensing requirement
to use minimum necessary bandwidth, the sidebands on each tone will be
+/- 220.5 Hz, so you really want the passband to be essentially flat
between 661.5 Hz and 2425.5 Hz, or receive with the tones all shifted
down in frequency to fit within the filter passband. As transmit will
use the same filter, you really need to do the same for transmit.
previous version of this email I attached a jpg of the spectrogram
plot, but evidently emails with attachments are not permitted here. I
can send you a copy directly if it would help).
The list guidelines suggest that would be attachments be placed in
personal web space.
Is it possible there is too much attenuation or phase distortion of
the 2205 Hz signaling element for easy WSJT operation? I have the
OPT1
Filter phase errors will cause group delay errors, which will distort
the signal. The audio chain on the K2 may also cause some cut off off
if you shift the tones lower.
filter adjusted for the best sounding ssb voice signal (according to
my xyl's careful listening). If it's necessary to move the filter up
150-200 Hz for WSJT, it will affect how my voice comes across in
ssb.
You can use the RTTY filter set to allow different filters for receive
data. I can't remember if these allow a different offset on the
transmit filter.
--
David Woolley
Emails are not formal business letters, whatever businesses may want.
RFC1855 says there should be an address here, but, in a world of spam,
that is no longer good advice, as archive address hiding may not work.
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