[GreenKeys] RS232 to Loop convertor for Dovetrons

[Roy Norris]

Hi Gil,

Ok, thanks very much.

On the new  RS232 to loop converter project, I do hope you can do it with 
speed conversion and a decent sized buffer.  I have just completed the 
exercise of trying to find 60 wpm gears for several model 28's and they are 
just about unobtainable now.  I finally got a set through Don House and the 
NADCOM Museum.  I bought  several gear shifts but they were exceedingly 
difficult to find (took me three months and each cost over $100).

On a recent eBay auction, a Dovetron unit with speed conversion went for 
over $500 when ones without speed conversion were going at $150.  It just 
shows how serious a problem finding gears for 60 wpm has become.

As I wrote you earlier, having the ability to optionally insert CR CR LF 
LTRS starting at the 73 character would greatly facilitate the use of 
mechanical RTTY  as so many of the computer programs today don't adequately 
provide for it and, when they do, the operators don't use the 
feature.  This would also require the inclusion of some sort of buffer as 
well. Someone else mentioned adding a character counter but just a light 
and an audible "beep" that would come on when you had typed 70 characters 
or so would be a nice feature to have.

Think about the possibility of including a common SELCAL.  This would be a 
great feature for a group of users who wanted to set up an RTTY group on 
one specific frequency and have all the machines activated by a common 
SELCAL.  Traditional autostart circuits are so prone to tripping by noise 
and off frequency stations.  This would be a big plus for un-attended 
operation.  Also great for un-attended copying of news if George is 
successful in getting RTTY broadcasting approved by the FCC.

I would vote for the separate box approach to facilitate use with TU's 
other than just the Dovetron.  Just connect to the Dovetron with BNC jumpers.

I would think provisions for connecting three devices in the loop would be 
ideal:  TTY printer, reperf, and TD.

Half duplex would cover most situations since few, if any, RTTY QSO's are 
conducted in full duplex.  A separate loop supply can always be used if 
someone wants to type to a reperforator while receiving on the page 
printer.  Alternatively, you could put two loops on the board, one keyed 
from the RS232 and one not keyed and both running off of the same power supply.

Their is very little ASCII on the ham bands or shortwave bands hence the 
low voltage, low current loop for the Model 33's and up would probably be 
superfluous without a baudot to ASCII converter for those wishing to copy 
RTTY.  However, the low voltage, low current loop would be nice for Model 
33 owners who want to drive their machines from their computers..

Just my two cents :)

Thanks very much for undertaking this project.