[GreenKeys] Fwd: The Flying White House 1947

[Nick England]

I'm still doubtful that this ART-13 is running AM with AFSK. Looking
back at the original photo (Thanks for posting a great mystery photo,
Don!!!), I see there is a switch lever for the add-on box with the
co-ax connection on the right hand side - the lever positions are
marked NORMAL (up) and TTY (down). Along with the "CAUTION: USE BLOWER
ON RTTY SERVICE" label, that sure looks like exactly what you'd have
for an ART-13 modified for FSK service.

The AN/SGC-1 was an AFSK TU used extensively on UHF, but I haven't
come across any evidence of use on HF. The Navy had FSK adapters for
their older HF CW/AM transmitters - some were just a simple reactance
tube modulator, others quite sophisticated replacement master
oscillators.
http://www.navy-radio.com/rtty-keyer.htm

Later, AFSK became pretty standard on SSB of course, but that's
another case altogether.

On another note, the gadget beneath the receivers appears to be a
diversity RTTY converter, judging from the markings on the Meter B
switch. That doesn't square with the AGA-1 description either.

cheers,
Nick K4NYW
www.navy-radio.com


On Wed, Feb 15, 2012 at 10:43 PM,  <WA5CAB at cs.com> wrote:
> OK.  I had a TT-30/AGA-1 once upon a time.  Still have the manual but I
> think that George has machine now.
>
> The TT-31 must therefore have been the functional equivalent of the
> TT-40/SGC-1.  My guess is that the black panel with two meters above and to
> the left of the operator could be the TT-31.  Running the T-47 for extended
> periods in AM with high modulation levels would account for the addition of
> the blower..  However, an encrypted AFSK system doesn't account for the
> coaxial cable going into the right end of the transmitter.  As the audio
> would have been on the secure side of the system, there would be no need to
> run it shielded
>