Ham Radio Teletype

[Qbus]

A project that I spent several months on from concept, design to completion. The goal was to find a way to use an obsolete messaging terminal from a Tactical Satellite communications system for Ham radio teletype. Had to resolve issues with different character sets, different word lengths and different baud rates but with the help of a couple AY-5-1013 Uarts and a hand full of 2716 ROM chips this is what I came up with.
See You Tube:

https://www.youtube.com/watch?v=tMiDnn5a_xM

 

[maxtherabbit]

I love listening to RTTY. It's almost musical

 

[NeXT]

The fact that you rolled the solution like that and opted against a modern microcontroller adds a considerable amount of charm. It also looks fantastic racked like that.
Good job!

 

[Qbus]

Gave using a computer a lot of thought but ran into a couple issues, first would have to have a system with at least two communications ports because of the different speeds. Second was the thing about the five-bit TTY using two different sets of tables depending on if the next character is a number or letter. Easy to use a decoder to recognize the LTRS/NUM select commands and have the appropriate ROM but not certain how I would do that with code.
Have another ROLM 1602 that I have to repair a second serial channel card for and may attempt to use that once I have both communications channels up and running being its so primitive that the serial cards support all the old slow baud rates but then the issue is would have to be able to deal with strings of characters being written into memory and then looking at comparing them to a table for conversion and writing out the opposite port.
I have only just learned how to work with one I/O operation at a time and am no where near the point of dealing with strings of data yet. Maybe that will be the next big project?

 

[charnitz]

Pardon the naïve question, but, in the video, while running the character generator, the terminal doesn't print out each character as it comes in. How does the terminal determine when to print out a line on the display? Are there CR/LF codes in the character generator sequence and the terminal buffers until it sees one?

 

[Qbus]

A lot of the early digital military teletype stuff had that as a annoying habit, they will buffer the entire line until they see a CR/LF and then print it. The UGC-74 printers do this and always hated that.
If you forgot to include a CR/LF statement in your last line the receiving station would never see it. Standard military messaging protocol always has you doing a couple CR/LF and then a last line of six N characters followed by a CR/LF

 

[alank2]

Looks awesome Qbus!

One of the struggles of modern ports is being able to divide it enough to get down to the very low baud rate. I am working on a control panel based 8080 computer that I wanted to be able to theoretically connect to a teleprinter. Sadly I have no teleprinter, but it came down to it is better for me to use a conversion type interface. My control panel computer can go down to 1200 baud, and then I would use a much slower microcontroller (running at 500 kHz) to convert from 1200 to 45 and do the character translation at the same time.