[Milsurplus] aircraft transmitter & dynamotor

[Morrow, Michael A.]

Hue Miller wrote:

> 2. How about sending distress messages, cw, via the push to=20
> talk button on the pilot's mic?  That would be real hard,
> right? From my limited trials trying this, the rate would be
> extremely slow, and rife with errors. I think also you really
> have to exagerate the dah length to distinguish the dits and=20
> dahs. I mean a mic like the RS-38.

Having tried the transmitter control box CW key on the GF, SCR-183/283
(BC-232), SCR-274-N (BC-451-A), and C-87/ART-13 controls, I think
sending CW from the pilot's position would be easier using the PTT
switch on a T-17 or RS-38, compared to using the control box key.  The
C-87 key, in particular, has a nasty feel.  Even better might be to use
the "throttle switch" PTT button if one is installed.  The key at the
control box just grounds the PTT line, so keying the PTT is electrically
the same as using the CW key.

I'd guess that most WWII military airborne CW usage would have been
slow, regardless of keying method.  My SCR-274-N manual recommends
keying below 12 wpm.  The AN/ART-13 is a real speed demon, being rated
for keying speeds up to 30 wpm.  I'd guess the SCR-287 was in between,
but probably closer to the SCR-274-N.

I'd love to hear what the CW signal sounds like from a dynamotor-powered
SCR-274-N (or ATA or AN/ARC-5) transmitter that is being keyed by the B+
keying relay in the modulator, as designed.  All transmitter B+ is
applied and removed with each key press and release!  Many hams cheat
this original design by continuously applying B+ and keying the
transmitter select relays in the transmitter rather than the B+ relay in
the modulator, but that is not an "authentic" mode of transmitter
operation if one is interested for history's sake in what the
as-designed system sounds like.

Mike / KK5F