[Milsurplus] Re TA -12 tx

[Mike Hanz]

As usual with the Bendix sets, it's not as easy as that.  The TA-12B, C, 
and D basically differ only in frequency range.  All are 28v using an 
MP-28BA modulator.  Only the uncommon TA-12F uses 12v, and it is paired 
with an MP-28CA modulator.

73,
Mike

Mike Feher wrote:

>I was under the impression that the suffix on the TA-12 denoted the
>operating voltage of either 12 or 24. The same with the MP-28s as I have one
>of each. 73 - Mike 
>
> 
>Mike B. Feher, N4FS
>89 Arnold Blvd.
>Howell, NJ, 07731
>732-886-5960
> 
> 
>
>-----Original Message-----
>From: milsurplus-bounces at mailman.qth.net
>[mailto:milsurplus-bounces at mailman.qth.net] On Behalf Of Mike Morrow
>Sent: Friday, November 19, 2004 1:02 PM
>To: Mike Hanz; pete williams
>Cc: milsurplus
>Subject: Re: [Milsurplus] Re TA -12 tx
>
>pete williams wrote:
>
>
>>The TA-12 (Bendix) was obviously used with a  receiver (RA-10? ?) ..
>>How was the companion rx muted when going to transmit ? ----- there
>>does not appear to be any PTT facilities with the tx or the external
>>modulator/dyno. Pins 12. 13 and 16 are mic inputs  to the  dyno /mod
>>but no tx/rx facilities obvious.
>>
>
>Mike Hanz wrote:
>
>
>>It's a bit circuitous, Pete.  The wire from microphone tip in the MS-18B 
>>jack box goes to pin 16 in the modulator/power supply through an MS-14B 
>>junction box.  Microphone sleeve runs through the same junction box and 
>>ends up at pin 2.  That's how it gets the PTT signal.  The set isn't as 
>>self contained as some other designs because you really need some kind 
>>of junction box to tie everything together.  See 
>>http://members.cox.net/aafradio/flightdeck/bendix1.htm for the piece 
>>parts.  Unfortunately, you also need an MT-51 control box to select CW, 
>>MCW, or phone - you can't do it from the TA-12 front panel.
>>
>
>I've never understood why those Bendix adjunct items are so hard to find.
>TA-12B/C transmitters and the associated RA-10D/DB receivers, and MN-26C
>RDFs are everywhere, many in near new condition.  MT-53B LF coils aren't too
>hard to find either.  But the MP-28BA modulator/dynamotor units are fairly
>hard to find.  The MT-51, MR-9, and MN-28C (as opposed to the common but
>oddball 28Y) control boxes are harder still.  Same thing with the RTA-1B
>10-channel HF transmitter-receiver.  It's pretty easy to find them in great
>condition, but not the rack and control box.
>
>Regarding the TA-12/RA-10 receiver muting system, I seem to recall that the
>only muting of the receiver comes from the antenna relay which grounds the
>receiver antenna lead on transmit.  Navy airborne sets seem to use that as
>the only muting method for the receiver, such as in the systems comprised of
>the ARB/ATB, ARB/ATC, ARB/ATD.  The USAAF systems using the BC-348 did an
>"honest" job of receiver muting by grounding the receiver antenna lead and
>removing high voltage from some of the receiver front end tubes.  Of course,
>that meant that these USAAF systems needed an external MONITOR-NORMAL switch
>to restore that HV in the receiver to allow netting the receiver to the
>transmitter.
>
>73,
>Mike / KK5F
>
>
>
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