[GreenKeys] IRV HOFF - RTTY Pioneer

[Jim Haynes]

We are fortunate to have had Irv when we did.  He had enough spare time
and spare money and an incredible amount of energy to do a lot of work
on TU design at a time when this was a very active topic in RTTY.  If
he were living today he would probably be in the thick of DSP work with
sound card modems.  I suppose we won't see any further development in
hardware TUs since so few of us need such a thing, and since it's so
much easier to get high performance, and to experiment, with DSP methods.
Eric Volpe's little demodulator is a special case, great for good
signals such as we get off the Internet but not something you would want
to use on HF radio under any kind of difficult receiving conditions.

One of the first, and arguably the best of the DSP modems for RTTY is
the K6STI RITTY program.  It is, sadly, no longer available and might
be unusable even if you could get it.  It was written for DOS on the
PC; and DOS lets you do some things that Windows and various DOS emulators
make impossible.  DOS let the application program take total control of
the computer, so that it was not subject to interruption by the
operating system.  Thus it gives you the equivalent of a dedicated DSP
engine.  RITTY is the only program I know of that synchronizes to the
character rate (requiring diddle be turned on for keyboard sending)
and thus knows exactly when to sample the filter outputs at their peaks.

There are a few tricks that so far as I know were never seriously tested
back in the era of hardware TUs.

Jim W6JVE