[Milsurplus] Re: aircraft transmitter & dynamotor

Sun, 26 Oct 2003 21:23:42 EST

Hue,

In sets that use the same dynamotor for both the receiver and transmitter, 
the dynamotor runs as long as the equipment is turned on.  SCR-183, 283, 522, 
AN/ARC-1, 2, 4, 12, GF/RU are all like this.  In sets with separate dynamotors 
for receiver and transmitter, the transmitter dynamotor runs continuously when 
the mode switch is set to CW or MCW and runs only when the microphone PTT 
button is pressed when the mode is set to AM (voice).  SCR-177, 193, 245, 274, 
284, 287, 506, 508, 608, 808, AN/ARC-3, 5, 8 (AN/ART-13 + BC-348), AN/GRC-19, 
ATA/ARA, ARB/ATB, ATD + ??, GP-(*) + ?, etc. are all like this.  For that matter, 
medium power AC operated sets are as well.  The BC-610 transmitter HV supply 
is on continuously if the mode switch is in CW and is keyed by the mic PTT 
button in Voice.

Not quite certain how to answer your other question, though.  If you had a 
voice-only set, or a multi-mode set in the voice mode I guess you'd say "Help!". 
 Or if you had your wits about you, "Mayday".  Certainly, trying to key a 
transmitter in CW when the mode switch was set to Voice would quickly trash the 
dynamotor and starting relay, not to mention that the chirp would be 
horrendous.

In a message dated 10/26/2003 7:57:37 PM Central Standard Time, 
[email protected] writes: 
> I have some questions on how WW2 aircraft transmitters and dynamotors
> worked together. I have to admit i've never really followed out the full
> system schematics in the manuals to see the big picture. Maybe some of
> you who have replicated full system setups can help me out.
> 
> 1. When does the transmitter dynamotor kick in? It cannot be spun up
> every time the talk button is pressed, right? And it would be a waste of
> power and longevity to have it run fulltime. But i don't recall any switch
> on the control boxes for receive/ transmit. Maybe when switched to "A1"
> the transmitter dynamotor goes on fulltime for cw.
> 
> I am talking about medium high power HF equipment. I mean like SCR-287,
> Bendix RTA-1, etc.  
> I can see how in some vhf set with only a few watts, like the ARC-4, you 
> could 
> run the transmit B+ all the time, no trouble.
> 
> 2. How about sending distress messages, cw, via the push to 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 dahs. I mean a 
> mic like the RS-38.
> 

73
Robert Downs - Houston
<http://www.wa5cab.com> (Web Store)
<[email protected]> (Primary email)
<[email protected]> (Backup email)

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