[GreenKeys] M28 features for RTTY operation today?

[Ralph Irish]

What a lot of 'Irv's enemies' didn't know was that after a few paper run outs, Irv came up 
with a stunt box fix that would not allow multiple LFs to take place unless some number of 
printing characters had been sent. So, some clown would sit there and type endless LFs, 
laughing all the time, not knowing that in most cases, Irv was sitting on his end, laughing 
even harder as the machine cycled and only one or two line feeds were accomplished. 

- - - - 

Not certain of the timeframe, but sometime later, Irv got to borrow some kind of 'mini-computer' 
(Data General comes to mind) and wrote routines to circumvent any such nonsense. All data 
from the TU had to pass through the 'Mini' thence to the Model 28's Selector Magnet Driver. 

He even wrote routines to make his 'output' have 7.5, 8, 9 and 10 unit code, with all of the excess 
being put into the STOP pulse. This made for some most interesting 'sounding' mechanical action 
from the Teletype, whether it was a Model 28 or 15, etc. Throughput was still very close to what 
it would have been with 7.41 or whatever. I'm certain that the mathematicians among G/K can 
do some number crunching and convert to OPM and come up with some exact number of WPM. 

Irv was a nice guy, and he was misunderstood by many. I was not 'one of his biggest fans', but 
you have to put credit where it belongs. Without his efforts, those 100 and some Model 28s would 
have been sold by Pacific Bell (or whomever) and never seen by any hams. You might say that he 
was 'ego driven' as are many creative people. His original Mainline TT/L from the early-mid 60s 
was almost a 'giant step' past the W2JAV units very commonly used by many, back in the 50s 
through the early 60s. Petersen's 1967 'revamp' called the TT/L-2 TU was almost as large a 'giant 
step' past the original TT/L, and that device won over many hams as far as striving for near perfect 
copy under varying band conditions. There were PC Boards made for most of the circuitry, and 
other PC boards for specific sets of bandpass filters and Mark/Space channel filters. A fellow in 
Texas whose name/nickname was "Curly" made some of these boards, and sold them for little 
profit. He provided manufacturer's part numbers for tube sockets and terminal strips and other 
items for those who wanted a great looking and performing TU. 

Over time, Petersen, with help from some Detroit area 'locals' came up with part value mods for 
the TT/L-2 and those who took the time to make the changes found the 'error rates' dropping a 
bit. 

At that time, Truman Boerkel, K8JUG (later K9JUG), worked for a "parts house" in the Chicago 
area and put together kits of parts for those who wished to have a finished unit work as Petersen 
wanted it to work. I suspect that there are still many of those 'kit sourced' TT/L-2 units working 
quite well, if they were not allowed to 'sit idle' for decades. (Nothing lasts forever!!) 

Petersen specified some special switches for the unit, and using another could have caused some 
'mode-switching glitches' and less than ideal print. Truman made sure that the 'house' had the 
correct spec-ed switches for these kits. (Not talking about rotary switches, but two and three 
position toggle switches.) 

I have very find memories of those days. I was fortunate to find a TT/L built with all 'point-to- 
point' wiring, on a 3" x 17" x 15" chassis, good 19" rack mount front panel and decent labeling 
on the panel. It served me for years. I had it on the summer "East Coast Autostart" channel, 
3637.5 KHz. My receiver was a TMC with crystal positions with 'hz-shift' of the crystal circuit 
for near exact freq setting. It also had a crystal socket for the BFO, for even better 'on the 
cycle' setting of the audio coming out of the receiver to the TU. My 80M inverted "VEE" was 
about 30 feet at the feedpoint and I had favorably located trees for the ends. One of the best 
time of my 'ham radio life' was that time period. I built (and still have) a simple small chassis 
crystal oscillator circuit with a piston trimmer that I plugged into my Heath DX-35 transmitter's 
crystal socket. By 'zeroing' stations on the air who were known for their precision, I stayed on 
freq, and had only one person ever question my signal frequency. (We were both off a little bit!) 

Those were the days!! 

73, 

Ralph - W8ROI 

- - - - 

Irv Hoff: K8DKC, Ann Arbor, MI later W6FFC in California; Military pilot, later airline pilot 
Keith Petersen: W8SDZ, Ohio, later Michigan resident. Lived elsewhere at the time of his passing. 
Broadcast Engineer in Toledo, Detroit, and other employment situations including 
Chief Engineer of some TV stations in the south. (Forgot details.) 

----- Original Message -----

From: "Russ Miller" <wa3frp at gmail.com> 
To: "Jim Haynes" <jhhaynes at earthlink.net> 
Cc: "Greenkeys" <greenkeys at mailman.qth.net>, "Nick England" <navy.radio at gmail.com> 
Sent: Saturday, February 23, 2019 2:59:36 PM 
Subject: Re: [GreenKeys] M28 features for RTTY operation today? 



    1. Non-Overline for the Teletype Model 28 




On a normal Teletype machine, when someone hits CR, the carriage will automatically come back but will not turn up a new line. This is a nice feature for RTTY Art but a real problem if you are trying to copy a weak signal and you are already receiving partially garbled text. 



Fortunately, the Model 28 machines can be easily converted to avoid overlining. This change requires no new parts and can easily converted back to factory stock in a few minutes. 



Here are the steps to make the change: 





        1. Remove the roll of paper 
        2. With the motor running, look at the top of the stunt box. 
        3. Hit the CR key and some slot will show activity. This should be slot 5, counting from right to left as you stand in front of the machine. 
        4. Hit the LF key and two slots should show activity. These should be slots 38 and 40, counting from right to left as you stand in front of the machine. 
        5. Leave slot 40 alone. 
        6. Remove the LP and take out the stunt box (after disabling all power). 
        7. Swap the universal code bars in slots 5 and 38 and reassemble the machine. 




Now, when the CR key is pressed, nothing happens. When the LF key is pressed, both CR and LF occur at the same time. 



You will still have to hit the CR key when you are transmitting. The CR character still needs to be sent to the distant machine. It may seem awkward to type the CR key and have nothing happen. But, the simplicity of this change, the fact that no additional parts are needed and that it works so well are huge benefits. 



I hope that this helps! 




Russ WA3FRP 

On Sat, Feb 23, 2019 at 12:36 PM Jim Haynes < jhhaynes at earthlink.net > wrote: 


I've forgotten the details, but one of the changes was because some 
of Irv's enemies were starting up his machine on autostart and sending 
continuous LFs to run all the paper out on to the floor. Auto-CR-LF is 
obviously good for radio because if you miss a CR or a LF you lose a 
line of print. And if you get a CR without a LF you lose a line of 
print. (Altho there were some TTY pictures where being able to overstrike 
was essential) 

If people using computer-emulated TTY are failing to send proper end of 
line characters then you aren't required to be able to receive from them. 

An electronic regenerative repeater is always good with a mechanical 
Teletype because of the problem of false starts and missing stops that 
result in several errored characters. 

--- 

"Ya can argue all ya wanna, but it's dif'rent than it was." 
"No it ain't! No it ain't! But ya gotta know the territory." 
Meredith Willson, The Music Man 








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