[RTTY] RTTY Mobile! WA9ALS is on the road now 14.083

[Kok Chen]

> John (WA9ALS/M4)

Wow, John drove all the way across the ocean?!   :-P

With PSK31, my guess is you need to keep the speed of the vehicle
low enough that the difference in phase of the carrier from one bit to 
the
next is much less than 180 degrees.

PSK31 is 31.25 baud; a bit time is of the order of 32 msec, and a 
wavelength
is of the order of 20m.

Let's say you want to keep 36 degrees (1/10 of a wavelength) coherency,
So you cannot travel away from the other station by more than 2 meters
(thats the 1/10 wavelength) 32ms, or 62.5m/sec or so.  That translates to
about 225 km/hr or 140 mph.

The vector between the two stations is also never at the worst case 
(i.e.,
you are not travelling directly towards or away from the other station) 
that I
imagined above.  Also, a wavelength is 21m and not 20m, so you have an
extra 5% headroom.

My guess is that mobile PSK31 is workable.  But maybe not in that 
Corvette,
or a Porsche on the autobahn (want to try it, Ekki?)

With my PSK implementation for the Mac, I do have to keep phase coherency
to within 36 degrees to get good print.  You may need to ask the XYL to 
move
  to the slow lane to see if a PSK31 QSO is easier to establish :-).

If the above craziness (carziness?) is correct, 10m mobile PSK31may be
tougher, and you may not even be able to get on the freeway with 6m!

73
Chen, W7AY