[MRCA] [MMRCG] Fast RTTY

[jkarlow at comcast.net]

Eugene - Another alternative if you want to have a Model 28 KSR be able to
have full adjustable speed between 60 and 100 WPM, you can also install the
LMU-10 Variable Speed motor. A lever connected to the governor would let you
set the speed. It comes with a tachometer generator unit that went to a
meter on the front of the machine which would display the operating speed.
Many years ago when I lived in the Washington DC area, these were fairly
common, most used by the CIA for their purposes. 

 

Jim KA8TUR

 

From: MMRCG at groups.io <MMRCG at groups.io> On Behalf Of W2HX
Sent: Friday, February 12, 2021 6:12 PM
To: MMRCG at groups.io; 'MRCA' <mrca at mailman.qth.net>
Subject: Re: [MMRCG] Fast RTTY

 

Hi Ray. I would venture to guess that 100 wpm is not exceedingly common. I
have a M28KSR that has the gear shift and I am sure others do too. But it is
less common. While I DEFINITELY applaud you for wanting to use rudimentary
(by today's standards) technology for this project, that speed conversion
issue might just be what would tip me over to an arduino or something. I
also wonder whether you could change the baud rate on the UART within the MX
terminal? The chip may be able to be re-wired for that speed. Alternatively,
you could potentially replace the crystal that operates the uart with an
Epson oscillator thingy with a frequency that corresponds 45.45 baud (from
75 baud). Just some thoughts. Good luck!
73 Eugene W2HX

 

 

From: MMRCG at groups.io <mailto:MMRCG at groups.io>  <MMRCG at groups.io
<mailto:MMRCG at groups.io> > On Behalf Of Ray Fantini
Sent: Friday, February 12, 2021 3:25 PM
To: 'MRCA' <mrca at mailman.qth.net <mailto:mrca at mailman.qth.net> >;
MMRCG at groups.io <mailto:MMRCG at groups.io> 
Subject: [MMRCG] Fast RTTY

 

Plowing forward on my 1980 digital RTTY project, going to be building the
input UART that will convert the digital level output of the Dovetron TU
this weekend. That will provide me with a five bit word that the ROM board
will convert to a seven bit ASCII word that the MX Tactical terminal will
understand.

The MX family of terminals run at 75, 600 and 2400 baud. I have the UART
that converts the seven bit word to a serial word the MX understands and
sends it to the MX at a blinding high speed rate of 75 baud. The real
problem will be going from the MX to the Dovetron at 60 WPM, going from 60
WPM (45.5 baud) up to 100 WPM (75 baud) is no issue. The problem occurs with
the way the MX Terminal works. You cannot transmit in real time. You have to
write to a buffer in the terminal and then go to the SEND function on the
terminal and dump the entire message at once. When going from 75 baud to
45.5 baud you would have to store data in the message to make up for the
added time required to clear the data thru the UART.

Long story short, wont have any issues reading 60 WPM traffic on the
terminal but looks like I can only transmit if both stations are running at
100 WPM

What's the feeling about getting some of the 28 people out there to get
those old teleprinters to chug along at that speed?

 

Ray F/KA3EKH

 

 

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[jkarlow at comcast.net]

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