[RTTY] Some basic RTTY questions

[Al Kozakiewicz]

The essential part is that the tones are separated by 170 Hz and that they're in the passband of your receiver and soundcard/software combo.  Transmitting using FSK, you have no choice on the absolute value of the tones - they're set by the transceiver firmware or through hardware in older radios.  With AFSK, you can set them anywhere within reason.

On receive with FSK, you can, in theory, set the VFO off frequency to get a "more pleasing" set of tones and compensate by fiddling with the MMTTY mark frequency to properly decode the signal.

 The main issue with doing any of this is operational in nature. With FSK you'd have to run split.  With AFSK everything tracks OK, but you'll have to do some math to figure out the correct dial frequency for, say, a spot.  Some logging programs will do the correction for you, but since I don't run AFSK, I don't know if they can correct for any arbitrary mark tone or only 2125.

Al
AB2ZY


-----Original Message-----
From: RTTY [mailto:rtty-bounces at contesting.com] On Behalf Of Michael Rapp
Sent: Thursday, May 29, 2014 8:55 PM
To: rtty at contesting.com
Subject: [RTTY] Some basic RTTY questions

Hi all,

I participated in the CQ WW RTTY last September and had a blast, but I tried to do things too much and too fast and burned myself out on RTTY (and ham radio).  I'm slowly getting back into things and I remembered just how much fun I had in RTTY.

(My interest was partially rekindled by re-reading Hank Garretson's, W6SX, profile in the past December's NCJ.  Hank reminded me that a tremendous amount of fun can be had even if one doesn't come anywhere close to winning.  For whatever reason, late last fall I got caught up in the frustration that my station and antenna would never allow me to reach anywhere near a winning score.  Hank's words reminded me that that is not the point.  Having fun is the point.  Thank you, Hank.)

In any case, I've decided to take it slower this time and do one thing at a time.  So, my first question is about that I am not understanding something fundamental about the RTTY tones.

It seems the most common mark tone is 2125, followed by 1275.  I've read in numerous places that many people set their mark tone frequency to be even lower, such as 915, as it is less fatiguing.

But, I'm set up for FSK.  My software (MMTTY) doesn't decide what my transmitted tones are.  My radio does.  My Yaseu FT-950 allows me to pick
2125 or 1275 and that's it.  So it looks like I can't set my mark tone to a lower frequency even if I wanted to.

Moreover, changing the mark tone makes no sense on receive as one is receiving the tone frequency of the transmitting station.  Am I correct or am I missing something really basic here?

My second question is on optimizing my receive audio.  My radio PC is an old server and does not have a built-in sound card  I'm using a cheap little USB sound card that has a mic in not a line in.  I receive my RTTY audio by taking the REC OUT of my FT-950 into a mixer (for sideband work) and then the tape out of the mixer that goes into my USB sound card's mic jack.

Is this okay?  I don't seem to be overdriving (or underdriving) the mic input at all and this is the setup I used for many many contacts in CQ WW.
 My concern is that I'm missing weak stations with this configuration.

Thanks everyone for your help.
--
/*/-=[Michael / KT5MR]-=/*/
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