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From: "Gary - G4WGT" <g4wgt@tiscali.co.uk>
To: <rsgb_lf_group@blacksheep.org>
References: <290328.96637.qm@web25405.mail.ukl.yahoo.com>
Date: Fri, 20 Jul 2007 10:50:16 +0100
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Subject: Re: LF: 500 RTTY first 2 way
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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" <g3ykb@yahoo.co.uk>
To: <rsgb_lf_group@blacksheep.org>
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