[RTTY] Death of RTTY?

[Kok Chen]

> The strongest signal in the bandwidth is going to
> capture the AGC and the weak ones just fade away.

Absolutely right, Mike!  And not just the receiver, but the
dynamic range of the entire demodulation chain, parts of
which are much less robust than the typical contest rig.

The problem with armchair contesters being enamored with
PSK31 has been the pure fantasy of being able to open up
your receiver bandwidth and just clicking away with a mouse
at signals on some spectrum display like a "waterfall."

Well, let us say you open up your passband to 2 kHz and there is
one station at S9+40, and a puny guy like me hitting your receiver
in the same passband at S2.

That is 82 dB of dynamic range you will need to dig me out.

OK, some the rigs we own might be able to handle that,  but YOUR
RUN OF THE MILL A/D CONVERTER IN THE SOUND CARD SURE
WON'T!

Most 16-bit sound cards are good for a little over 50 dB of dynamic
range, and decent 24-bit converters are barely good to 90 dB.

Add a few more strong signals in the passband, and even the very
good A/D converters could not handle it.

To be able to handle the harsh environment of a contest, you
would end up having to narrow down the RF/IF bandwidth so a
big signal won't destroy that puny GU0 (:-) signal whose mult
you desperately need.  Bye bye, waterfall tuning.

Thus, you end up with no tuning advantage using PSK31, and you
have actually a distinct disadvantage since you now have to center
the PSK31 very carefully in a narrow passband; something that even
a clumsy oaf as myself (and a cross banana display) can manually
handle using FSK.

73
Chen, W7AY