[Milsurplus] Re: Navy Morse Code Inker

[Brooke Clarke]

Hi Rick:

The GRA-71 is the keyer used by a number of countries and agencies to send CW 
at 300 words per minute.  See:
http://www.prc68.com/I/GRA71.shtml
http://www.prc68.com/I/GRC109.shtml
http://www.prc68.com/I/GRA71_316.shtml  <- UK version

It was used to key HF transmitters which were modified to allow the fast 
keying.  No human can receive code at this speed so it was recorded at the 
receiving end.  Note that the S. Morse patent is for a left-right type (not 
up-down) pencil recorder.  It was later that the telegraph operators found they 
could read Morse by ear that the pen recorders were dropped from service.
http://www.google.com/patents/about?id=Xx5AAAAAEBAJ&dq=patent:1647
Note the sending mechanism is type with bumps, not key is used.
I have cleaned and bookmarked 1647.  It's about 2 MB if you want a copy send me 
an email.

I'm guessing that if you divide the length of a new spool of paper by the 
highest feet per minute rate the time that a full spool will last is not very 
long.  The key benefits of the GRA-71 were to minimize the time of transmission 
to defeat DF locating the source of transmission and that an intercept by any 
human would not be able to do anything since you needed a way to record.

The GRA-71 probably was used as part of a spy radio by the CIA.  They were also 
used in Vietnam by forward observers and the receivers for these probably would 
have been on nearby ships.  [All the battery powered HF combat radios I know 
about are aimed at NVIS propagation.  i.e. they are for ranges of up to a few 
hundred miles, not DX coms.]  I'm not sure how the Navy worked.  For example 
would the RD-110 or RD-112 be on a ship with guns that can hit land targets in 
Vietnam or would it be on some other ship that would relay the information to 
the ship with the guns?

-- 
Have Fun,

Brooke Clarke, N6GCE
http://www.prc68.com