[ARC5] T-30 throat mic.

[DSP3]

The T-30 is a dual element carbon mic that emulates a single-button 
carbon mic.  They are connected to the same mic circuit in radio sets 
that any hand-held, mask, or otherwise, would be.  The physics are about 
the same as currently used with electronic larynx equipment .  There is 
no adaptor, per se, just the proper two-pin connectors.  PTT was 
provided (typically) on the yoke or on a cord at the crew station.  
Transmitters like the ART-13 have a separate PTT line to accommodate 
this kind of remote PTT.   What Gen. Savage did was also typical.  One 
had to sort of juggle the mic to get the best sound, as heard via 
sidetone.  The P-80 originally used a throat mic with the P-3 helmet, 
until the newer oxygen masks had a mic cavity molded in.  As I've 
mentioned before, the military aviation moved to dynamic mics and 
headsets in the 1960's.  Ground radios followed.  The radio sets, 
themselves, remained carbon-level input with the attendant carbon mic 
bias voltage.  The dynamic adaptors use the carbon bias as Vcc for the 
small amplifiers installed either within headsets or via external 
adaptors such as the old MX-1646.  Aircraft and helicopters with the 
NATO U-90-series 4-pin connectors (also referred to as helicopter plugs 
(sic) )will generally have an adaptor installed somewhere on the 
airframe.  If not, then the headset must have one.   New, commercial 
helicopters may have an entirely different type of connectors and 
utilize proprietary headsets.  They may have been made by David-Clarke, 
but these connectors are not what one generally sees.  At a recent AOPA 
fly-in, I talked with a rep from one of the international rotary-wing 
manufacturers about these new connector schemes.  He simply iterated 
that they were typical to new manufacture and that they supplied the 
required headsets with the aircraft.  I asked the price of a headset for 
the displayed helicopter and he told me that they were about $2500, 
each.  So much for your standard D/C or $1000 Bose!!  Anyway, the T-30 
is nothing special, mic-wise.  I have a couple of new ones in the box 
but will probably never use them.  As a kid, I did try one out on a 
Gonset.  As I recall, it did work OK. Of course, that was in probably 
1958, so the mics were not too old!

Jeep - K3HVG



On 1/12/2015 5:03 PM, Richard Schumann wrote:
> >olding the microphone and keying it in the bargain,
>
> Hmmm...that begs the question as to how the T-30 was keyed....button 
> on the yolk?
>
> Curious minds...etc.
>
> Richard kn7sfz
>
>
>
>
>
>
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> On 1/12/2015 13:52, Mike Hanz wrote:
>> I think enthusiastic deployment in the 1930s was driven *far* more by 
>> the "hands free" feature than intelligibility, Ken.  There were just 
>> too many things for the pilot to do without adding the responsibility 
>> of holding the microphone and keying it in the bargain, especially in 
>> an emergency.  It was another one of those "seemed like a good idea 
>> at the time..."  And, as my UK correspondent indicated, it did seem 
>> to work for some people. Perhaps it was the British accent? :-)
>>
>
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