[ARC5] T-17 Metal 1942 or Plastic 1944 for 1949 GRC-9?

[Richard Knoppow]

      My T-17 is about like yours, its plastic and made by Universal 
Microphone.  The holes do not have to be large to admit sound. Also, the 
small holes are part of the acoustic network of the microphone, they 
provide some damping to the diaphragm. Evidently more than one design of 
carbon element was used in the T-17 so the cap design may reflect this. 
The RS-38 has the same arrangement, three small holes in a line.
     It would be interesting to know where the design originated. 
Several companies made hand held carbon mics for radio use by the mid 
1930s, perhaps the T-17 was adopted from one of them.  The general 
design suggests the advanced engineering of Western Electric.


On 9/14/2016 6:47 AM, Don Merz via ARC5 wrote:
> The metal 1942 one I have has a pattern of just 3 pin-sized holes. Hard
> to see how that helps much. It was made by WE. The black plastic 1944
> T-17-B version has seven much larger holes at the mouthpiece.
>
> I also have 3 more of these in bad shape. Two metal ones are dated 1935
> (!) and 1939, MFR not identified. They I have a 1944-issue T-17-D
> version in olive drab plastic.
>
> The metal ones ALL have the 3 tiny pin holes in the mouthpiece
> regardless of date. Both plastic ones have the 7 larger mouthpiece holes.
>
> 73 Don merz N3RHT

-- 
Richard Knoppow
1oldlens1 at ix.netcom.com
WB6KBL