[GreenKeys] 2018 RTTY Roundup, and doin' it Heavy Metal

[epvgk at limpoc.com]

On Sun, Aug 06, 2017 at 10:31:27AM -0500, Mark Hall wrote:
> I mentioned my choice of machine- a model 19 I have to get to Oklahoma
> first- the original "ASR". One of its former owners was a ham who used it
> for RTTY. In the back compartment of its table, not far from its REC-33
> power supply are two brackets that hold a "BUO" (a circuitboard of unknown
> origin- most possibly some ancient RTTY interface!) Among its goodies is a
> large cookie tin with the owner's original QSO tape, along with some other
> tapes- RTTY pics, a QSO card and other things. So cool. It has a pedigree.
> And I want to return it to the airwaves to what it used to do! I mentioned
> several TU's I had to work with as well, and Dave offered his insights:
> 
> "For your Model 19, I would recommend any of the HAL TU's ie., ST-5000,
> ST-6, ST-6000.  These will provide a direct conversion of AFSK to Loop (I
> think 60MA for your rig - but not sure) and loop to AFSK.  So you only need
> one box between your radio and teletype."
> 
> The bull is charging... ears tucked back, horns down, nose ring flapping...
> Dave's reply offers some really great advice:
> 
> "I think you are ready to rock and roll - I would prefer the ST-6 to the
> other units although your Dovetron should be easier to tune - with the
> Mark/Space scope and all - I just like the HAL stuff and when the
> opportunity presented itself, I was able to buy from HAL a NOS ST-5000 and
> NOS ST-6000 - seems they found the units hiding in the warehouse.
> 

Having experimented with this setup myself (though not for contesting) I have a 
couple of comments.  The ST-6000 (probably 5000 too) has a nice feature where it will 
detect that you've started typing and toggle a signal line which you can use to key 
a transmitter, and it will switch back after a short delay, which means no tx/rx switch 
needed. It also has an AC outlet you can use to switch on a TTY when data is detected
and then off again after a couple minutes idle, for unattended reception. 

The AFSK frequencies are fixed and With 170hz shift this works out ok, but with wider 
shifts (like when talking to people using 850hz shift military gear) the higher tone 
falls outside even the widest transmit bw filter on any radio I have, so cannot be used. 

Another option on some Icom radios (I use an IC7000) is a "native" FSK RTTY mode
where to transmit you feed it an on/off signal to shift the carrier, rather than 
feeding audio tones to the radio. This works nicely because you don't have to worry 
about audio levels, etc.  http://heepy.net/index.php/Keying_IC-7000_fsk_from_tty_loop

eric