In digging into a M28 ASR, I think I have stumbled
across some of the differences between Army & Navy TTY
communications. All the schematics for M28 KSR & ASR
units that I have seen, show just one loop, tying the TX
& RX circuits together. (Aux reperf in a M28 ASR
typically has its own loop.) M28s are wired such that
they are very flexible and can be wired to separate TX
& RX circuits, but that is typically not how they are
shown on system drawings. Th AN/UGC-6 (M28ASR w/aux
reperf) schematic (fig 12-38 from the Navy manual ) does
not show an option for full duplex (separate TX & RX
loops) operation.
Nick says that full duplex was not used much (if any) in
the Navy TTY comms, but his page,
https://www.navy-radio.com/circuits.htm
does mention full-duplex operation.
In 1950, the Army (and Army-Air Force) started buying
Kleinschmidt equipment exclusively (although they did buy
some M28s later.) All the Kleinschmidt units, TT-4,
TT-76, TT-98, AN/FGC-25 were set up for full duplex
operation with separate cables or jacks for TX & RX.
The standard Army wire-line modems (TH-5 & TH-22) used
with the TTYs were capable of both simplex (2-wire) and
full duplex (4-wire) operation. Mobile RTTY huts
(AN/GRC-26, -46, -122) could all be operated full duplex,
though simplex was the norm. (the AN/GRC-142 is a simplex
GRC-122.)
I was a TTY repairman in the Army Security Agency. In Viet
Nam in 1967. I was in the 337th Radio Research Co.,
supporting the 1st Infantry Division. We were located near
the Division HQ and had outstations (AN/GRC-46 huts)
positioned with the forward located 1st ID Brigades. We
also had a link to our battalion HQ and that link carried
a lot of traffic; so much so that it was run in full
duplex mode, with messages going in both directions,
simultaneously.
The outstations had tape facilities (TT-76s), but our
company comm center just consisted of a hut (AN/MSA-?)
with four TT-4 printers, 4-5 KW-7 crypto units and four
TH-5 modems in it. So all outgoing messages had to be
typed on-line. Imagine typing a message on a printer
while another message is being printed!
The Army did have medium-sized comm centers in trailers or
vans and big, fixed station comm stations, but I never saw
them. I did work on a 12 channel tape-relay center that
was in a 38 ft trailer..
So maybe some of the difference between Army & Navy
operation was due to the Army units being smaller and more
spread out; vs. the Navy with concentrations of operations
on big ships. The Navy's use of multiplexed RTTY may have
given them enough channels that they did not need to
operate full-duplex.
Just some thoughts.
Have fun,
Duncan
K2OEQ
31J30
On 08-Apr-23 16:24, Nick England wrote:
See also
They just weren’t used in full
duplex (except if the aux typing reperf was
independently connected). Normal installation
was to the C-1004 box that you manually switched
from CFS REC to CFS SEND. (The TONE position was
for hookups that automatically keyed the xcvr,
usually UHF).
I guess I just don’t understand
when you would run full duplex using a single
TTY.
If you wanted to receive while
transmitting you just used an additional TTY
printer or reperf.
Read more about the Navy’s view of
RATT
And
