[Collins] Astatic Mike Element

[Dr. Gerald N. Johnson, electrical engineer]

Other better microphone elements will fit the D-104 case, even an
electret. I used a Shure R-5 communications element with restricted
bandpass which avoids the excess high frequencies of the original D-104
(made for AM with receivers using a rounded shoulder passband that
rolled off highs) which can overdrive the audio stages and balance
modulator of some tube radios. The Shure R-5 is no longer available, but
there should other microphone elements of similar sizes. A little bit of
foam or fiberglass pad behind the element can hold it to the screen and
retain the appearance of the D-104 but give far better performance.

73, Jerry, K0CQ, Technical Advisor to the CRA
-- 
Entire content copyright Dr. Gerald N. Johnson, electrical engineer.
Reproduction by permission only.