Unlike almost all modern mics, the original D-104 has a shaped frequency response curve for optimum speech quality. It has a broad peak in the 3 kHz range to pick up the sibilance essential for intelligibility, with good roll-off characteristics at the higher and lower frequencies.
Since filter SSB rigs (like the K2) became the norm, I've noticed that more and more "communications mics" are simply the same old "hi-fi" elements packaged for Ham use. They depend upon the filter characteristics of the rig to limit the high and low frequency response, and generally do not provide any rising characteristic in the 3 kHz range that can produce the clear, bright audio that helps intelligibility, especially when copying a signal under rough conditions. Remember that when the D-104 came out, rigs didn't have filters! The speech was shaped slightly by choosing the right combinations of resistors and capacitors in the "speech amplifier" but generally any frequency between a few Hz and 10kHz (or more) that came into the mic went out the antenna, so a mic with proper shaping was an essential element of any good 'phone station back then. It's a great mic and a real icon. If yours has the original element, it may well be a Rochelle salts crystal element. Of so you're fortunate it's survived. They are easily destroyed by physical shock (knocking the mic over or dropping it) and temperature extremes. If you open the "lollipop" top, you'll see the element suspended in rubber inside the ring to help protect it from shock. The Rochelle salts crystal is also water soluble. If exposed to high humidity for any length of time, they dissolve! The element was hermetically sealed when it was made, but it seems that some of the seals fail over time (or curious fingers broke them). Rochelle salts elements were replaced by ceramic elements in most microphones at some point in the late 50's and 60's , but I don't know if Astatic ever went to a ceramic element for the D-104. Ceramic elements are lot more stable and strong, but not virtually indestructible like most modern dynamic and electret mics! Without specific data, I'd assume it's a Rochelle salts crystal and treat it like "royalty". After all, among mics, the D-104 definitely qualifies. Ron AC7AC -----Original Message----- I have been reading about the different microphones used by fellow K2 owners. A fellow ham encouraged me to try a vantage, (1960s) D-104 crystal mic for the K2. I had been using a Kenwood MC-48B and it was working OK. I knew that the straight D-104 mic would not work with the K2 as crystal mics are hi Z and the modern solid state Mic inputs are low Z. One model of D-104 however has an amp in it's base and it works fine. I get better signals quality report with the D-104 then my previous mic. I don't mind that the mic towers almost a foot over my K2 as I have big hands anyway. Just another Idea. Don...KA7L _______________________________________________ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
