[GreenKeys] GRC-26

[Duncan Brown]

Thanks to Ken for his description of the GRC-26A.  One additional note; 
in the 1950s the Teletype Corp. equipment was slowly phased out and 
replaced by the new Kleinschmidt line. Some GRC-26As used the 
Kleinschmidt TT-4 page printer along with the Teletype Corp TT-56 (M14) 
reperf & TD.  Later versions used the Kleinschmidt TT-98 page printer 
and TT-76 reperf.  See  http://rattrig.com/AN-GRC-26/26.htm  for 
pictures and equipment listing (also downloadable manuals).  The 
military used "RATT" for "RTTY".

We had a GRC-26D in Viet Nam and it used the KW-7 encryption box.  By 
the mid-late 1960s all Army RATT equipment was wired for encryption 
equipment.  If your circuits didn't require encryption, you got a "dummy 
box" to replace the encryption equipment (so that the cabling was always 
the same).

The AWA Museum has most of the pieces of an AN/GRC-26A (mainly missing 
the O-39/TRA-7 FSK VFO and maybe a junction box).  I hope to build a 
GRC-26A mock-up for the new Museum.

Good luck with your project Ken & have fun,

Duncan Brown, K2OEQ
USASA  31J

Chief TTY operator & repairman
AWA Communications Museum
http://www.antiquewireless.org/
http://www.antiquewireless.org/museum/museum.htm  (present museum)
http://www.antiquewirelessmuseum.com  (future museum)




On 02-Apr-11 19:49, Ken Kinderman wrote:
> In response to few queries as to just what the GRC-26 is, here is a brief
> rundown...
>
> The GRC-26 is a transportable shelter, about 7' x 7' x 14' on the bed of a
> GMC M-211 two-and-half ton truck. It doesn't have to be on a truck. Dropped
> onto the ground, it can be called an MRC-32.
>
> Mine is the -A version. It uses:
>
> - a BC-610H and BC-939 Tuner
>
> - two R-388's two TG-7B's (modifed by B&W into something called a TT-55 but
> still a TG-7B).
>
> - A Model 14 Typing Reperf and the accompanying TD
>
> - A control unit that routes the TTY lines inside the shelter
>
> - A dual diversity frequency shift receive converter that works off the 2 IF
> outputs of the R-388's
>
> - A Frequency Shift exciter O-39/TRA-7, essentially a 90 pound VFO with F.S.
> capability, that feeds the BC-610
>
> - A couple of LS-3 speakers
>
> - An A-11 aircraft clock in a cute little box
>
> - A pair of EE-8 field phones ("Run a pair of wires from the interior of the
> GRC-26A to the cab of the truck in order to communicate with the driver."
> Talk about hands-free driving....)
>
> - Lots of other accessories including "Broom, floor"
>
> - Great big transmitting whip, and provision for three smaller receive whips
>
> - Storage straps on the side of the shelter for poles for two big dipoles...
> the preferred setup for dual diversity
>
> The entire left side of the shelter is taken up with a monster storage
> cabinet.
>
> The earliest version used a pair of BC-342's (110 vac version of the
> BC-312), modified for increased stability.
>
> Later models, down to the -D version used later model TTY gear (RATT as the
> manuals call it), along with R-390A's and a T-368.
>
> The purpose of all versions was the same: basically tactical or mid level
> TTY origination and relay, along with voice capability. Some guys who used
> it in the 50's and 60's report the inclusion of encrytion and code burst
> gear. CW was an afterthought: J-47 key on a leg clamp. Because it used IF
> detection for the TTY signals, it was also possible to voice modulate the
> BC-610H while transmitting and receiving frequency shift TTY. By using
> separate receive and transmit frequencies, full duplex operation is
> possible, using voice and TTY simultaneously. Talk while typing, so to
> speak.
>
> Curiously, you throw it from R to T with a big clunky switch on the C-808
> control unit... the PTT line from the BC-614 speech amp connected to the
> BC-610H is left unconnected. So using either the T-50 or the T-17 for voice
> required flipping the switch and still holding down the mic. button.
>
> As Jack knows, I have been taking my time over the years first with cosmetic
> refurbishing of the shelter itself, then with the radio gear. I bought it
> from Fair Radio years ago and it was a mess externally. But inside, it was
> like a time capsule from 1952, including spare ribbons that still type.
> Nonetheless, the TTY gear hadn't been touched in almost 60 years, so as
> great as those machines are when they are running well, they needed major
> overhaul, which I am just getting around to now.
>
> Anyway, that's the short version of the story. Then there's the truck... ten
> tires and two heavy duty batteries among other babysitting chores...
>
> 73,
>
> Ken
> W2EWL
>