[HBR] Microphone Available

[Mike Hanz]

TC Dailey wrote:
> There are two mics that I came across while a Radioman in the Navy.  The 
> Navy BLACK one has the button on top, and a rubber strain relief on the 
> bottom..... the other famous one is a UNIVERSAL... you can see a picture of 
> one in their ad, in the 1945 ARRL Handbook... the button on this one is 
> OVERSIZE, and on the side... many of these were grey, green, or a mix..... 
> but not black.
>   

You've done a great job at describing the two primary aircraft 
microphones available before and during the war.  There's an overview on 
them at http://aafradio.org/flightdeck/Peripherals-mikes.html for those 
who are into minutia.  The gray T-17 was an unprotected aluminum casting 
that probably characterized the majority of T-17 mikes we encounter 
today.  An NOS version will look almost white in color.  A green color 
simply indicates that it had an oxidation protectant applied over the 
aluminum...I have a couple of those here in the shack.  The black 
versions were Bakelite based, and not quite as indestructible as the 
metal versions (but pretty near!) 

The problem with the hand held microphones was the need to use a 
hand...  The search for a hands-free alternative during the war led down 
several paths, but my favorite in the shack is the H-46/UR - 
http://aafradio.org/flightdeck/Peripherals-headsets.html has an overview.

> Most microphones used in WW-II were ALL carbon-granule types - they're just 
> TOUGH.  If it doesn't work really well, or has poor audio quality, SMACK THE 
> SNOT OUT OF IT on a table or the floor.  (works for old telehone 
> "transmitters" too)... this loosens the carbon granules and it'll start 
> working correctly again.

Well, to a degree.  I have encountered cemented buttons that would not 
come back regardless of the shock administered, and believe me, I have 
ways of administering significant force pulses here in the machine 
shop!   :-)   Response to the rap method varies all over the place, and 
sometimes it's bet to bite the bullet and simply replace the element 
with another one.  It is perhaps interesting that two of the WWII 
references on microphones here have test procedures that administer a 
calibrated series of raps to the microphone before testing.  The carbon 
mikes were extremely reliable but they didn't hold a candle to the 
British dynamics when it came to intelligibility.

73,
Mike  KC4TOS