[MRCG] RTTY net

[Mark J. Blair]

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/