Hi Brian, LF,
Thanks for your mail Brian.
I have previously received Graham's several transmissions using PSK but as
that required a linear Tx I was unable to reply, Graham pointed out to me
that the RTTY program MMTTY featured a setting for FSK output via the COM
port which would anable me to drive my DDS VFO using the CW offset as I do
for DFCW & the G0MRF class D Tx.
I looked at the possiblity & found that I only required to modify my
QRSS/DFCW interface by switching the FSK drive from DTR to TxD so I fitted a
switch to allow both modes when required. That worked fine but I had to be
able to Tx & Rx narrow shift. The prog MMTTY allowed me to Tx down to
whatever shift I set in the DDS VFO offset so I tried the preset 23 Hz shift
but found I could not Rx very narrow shifts with MMTTY. I downloaded MixW218
& that produced 100% copy down to 30 Hz shift so I set that as my standard,
Tx with MMTTY & Rx with MixW218 but it was hard work swapping programs for
Tx/Rx.
Graham used MMTTY prog at 25 Hz shift frequency 503.6 KHz using a audio
feed (AFSK) to the MA1723 exciter (I think that is RACAL) followed by a
linear amp. I think that if Graham could bring his shift up to 30 Hz I may
get a more solid copy.
The MixW218 will not do the COM FSK drive like the MMTTY so I must try to
use MMTTY for both Rx & Tx if I can get the profile right or maybe go for a
linear Tx design.
I hope that helps.
73
Gary - G4WGT - IO83qp
----- Original Message -----
From: "brian hodgson" <[email protected]>
To: <[email protected]>
Sent: Thursday, July 19, 2007 10:47 PM
Subject: Re: LF: 500 RTTY first 2 way
Hi Gary & Graham -
Congratualtions on the 500 kHz RTTY QSO.
I once tried to stir up interest in RTTY on 136 KHz but got no takers.
I've used PSK on 136 but that needs linear amps and not many LF ops have
such kit.
However, almost any transmitter can be used for FSK RTTY. I'd be most
interested to hear how you produce the FSK signal.
Regards - Brian
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