[RTTY] Omni-V and FSK

[Kok Chen]

On Wednesday, April 2, 2003, at 06:45  PM, WA9ALS - John wrote:

> However, hardly any (?) new rigs actually shift the oscillator.

The Omni-VI does.  Keys a local (RF) oscillator, as a consequence
the distortion products, if any, are way outside the band in use.

It is a "cleaner" solution, albeit more expensive to implement properly.
Over time, keeping the shift at precisely 170 Hz can be a chore on
the Omni, but then, many signals from sound card users are not
precisely 170 Hz, anyway :-).

But we are bordering on the esoteric when choosing between true FSK
and AFSK.  As with modifying rigs to minimize CW key clicks, emitting a
cleaner RTTY signal will only improve the other people's contest scores,
HI.

> Most DX spots, skeds, etc are quoted in MARK
> frequency. Depending on your rig and its setup, if you're using AFSK, 
> your
> dial will be off from the actual MARK frequency by 2125 Hz.  Thus when
> you're contesting and see a spot for a hot mult at 1408300, you might 
> think
> he's not there.  However, you might actually find him at
> 14.081 (14.080875).

Isn't it the other way around?  An LSB rig showing 14.081 suppressed
carrier frequency will be emitting (and receiving) a mark tone at 
14.079.

If you see a spot by a well-behaved RTTY op at 14.083, you'll need to
tune an LSB rig to 14.085, not 14.081.   (With an LSB rig, all 
emissions are
lower in frequency than the suppressed carrier (dial) frequency.)

People like WS7I and AA5AU spot unfailingly at the mark frequency :-).

73
Chen, W7AY