On Tuesday, August 28, 2001, at 01:17 PM, Ekki wrote:
> Indeed, 250Hz is
> working less good than 350Hz if the signal is noisy or has flutter.
Hi, Ekki,
By noisy signal, do you mean a badly modulated signal? If it
is band noise or QRM, then using a wider filter should make the
signal-to-noise ratio worse, not better?
Also, does flutter also increase the bandwidth of an RTTY signal?
I am always curious what polar flutter really is. Is it multiple arrival
time/phase of a signal?
Does anyone know if Rayleigh fading also broadens the FSK
spectrum appreciably?
I use two sets of filters on my 1000MP. One is a 250 Hz/250 Hz
pair (both INRAD) and the other is a 400 Hz/500 Hz pair (the
400 Hz is INRAD, the 500 Hz is Yaesu).
For me print has invariably been better using the 250/250 pair.
Ditto with my FT-990. I have a 250 Hz filter and a 500 Hz filter
on that rig, The 250 Hz one always provides better copy with 170 Hz
Baudot.
Granted, these filters don't have infinite slopes, either :-).
> It get's worse when 200Hz shift are used, as it is unfortunately happing
> more and more because it's the standard shift for Pactor-1 and some TUs
> use
> the same shift for all modes.
During the Slovenian contest, I only remember one station with a 200 Hz
shift. I think the more widespread use of Sound Cards is actually a
help here.
73
Chen, AA6TY
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