[MRCG] RTTY net

[Steve]

Mark,
I'm not absolutely certain about this but I think anything greater than
170 Hz shift is now forbidden on the HF ham bands now. Not that
I'm going to say anything as I ran 850 Hz for years back
in the day, but worth checking out.
                      Steve W6SSP
----- Original Message ----- 
From: "Mark J. Blair" <nf6x at nf6x.net>
To: "West Coast Military Radio Collectors Group" <mrcg at mailman.qth.net>
Sent: Sunday, July 27, 2014 3:35 PM
Subject: Re: [MRCG] RTTY net


> I've been looking over specs of various military sets, and the most 
> constrained one that's likely to appear on the MRCG Clatternet looks like 
> an AN/PRC-47 equipped with a CV-2455 converter. I'm assuming either a 
> modified converter (possibly marked "MI"), or a late production converter. 
> Early production converters will have mark/space reversed.
>
> These are the PRC-47+CV-2455 constraints if I understand everything 
> correctly:
>
> * Fixed 1 kHz tuning steps.
> * USB only
> * AFSK mark tone fixed at 1575 Hz
> * AFSK space tone fixed at 2425 Hz
> * 850 Hz shift, mark low
>
> !!! If anybody here has an early-production, unmodified, CV-2455, please 
> speak up. Otherwise, I'll assume that we're only likely to encounter newer 
> ones. !!!
>
> So, I propose that we set things up to make them work smoothly for a 
> PRC-47 + late-production CV-2455, and let the more flexible rigs 
> compensate. This will mean that the true FSK rigs will need to tune to a 
> weird frequency ending in x.575 kHz, but at least they can cheat by 
> zero-beating to somebody with a newer system.
>
> If all goes as planned, I'll try to come up on the air with my modern 
> solid-state gear tonight (Sunday) on 3601.575 kHz at 8:30 PM Pacific time. 
> Here are the parameters:
>
> * PRC-47/etc. channel frequency: 3600.000 kHz
> * Shift:                         +850 Hz (mark low)
> * Actual mark frequency:         3601.575 kHz
> * Actual space frequency:        3602.425 kHz
>
> For users of PRC-47, GRC-106/122/142:
> * Tune to 3600.0 kHz
> * 850 Hz mode, normal shift (I think!)
>
> For users of GRC-26D, GRC-46, etc. (true FSK rigs):
> * Tune Tx to 3601.575 kHz. Yeah, I know, just zero-beat me. :)
> * Normal shift (I think!)
>
> For users of modern computers with a sound card and solid-state 
> transceivers: I suggest the following settings which differ from ham band 
> conventions, but should (I think) be less confusing. Your mileage may vary 
> depending on equipment and software capabilities.
> * Tune radio to 3600.000 kHz.
> * Use USB mode.
> * Set modem software for 850 Hz REVERSE shift.
> * Set AFSK tones to : 1575 mark, 2000 center, 2425 space.
> * Set line endings to CR-CR-LF if possible.
> * 45.45 baud, 5 bit Baudot code, of course.
>
> Ugh, all of these stuff makes my head swim. :)
>
> Comments? Corrections? Questions?
>
> This will be an experimental session, not a formal net. I need to get a 
> bit more experience before I try putting together a real Clatternet 
> schedule. I'll have email access via my phone. I'm even open to using 
> something like Twitter as a back-channel for coordination if anybody other 
> than me here knows how to use it. :) I like the old gear and new-fangled 
> stuff equally well, and I don't mind mixing it together.
>
> Someday I'll be on the air with REAL radios (they have motors, you know), 
> but for now I'll limp along with my modern ham gear.
>
> -- 
> Mark J. Blair, NF6X <nf6x at nf6x.net>
> http://www.nf6x.net/
>
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