[AMRadio] Xtal mike


John Coleman wa5bxo at pctechref.com
Mon Mar 14 18:38:55 EST 2005


	This is correct, and a lot of the "pre-amped" microphones or very
good and some or not.  I used an old dynamic microphone case and pulled the
guts out of it.  It had been in a flood.  Then built a preamplifier and
condenser microphone on a small PC board and installed it in the old
microphone case.  I actually used two condenser microphone cartridges from
Radio Shack.  I don't remember the number but they were about dime size
round and thick.  I think I used three transistors but I don't remember the
circuit as that was several years ago.  My wife, Vickie, helped dye the new
spit cloth and glued it in.
See the picture at 
http://wa5bxo.shacknet.nu/HAMPICTURES/Pictures/Ham%20Radio/Mic.jpg
The LEDs were a small optical add-on.  

John, Coleman
WA5BXO

-----Original Message-----
From: amradio-bounces at mailman.qth.net
[mailto:amradio-bounces at mailman.qth.net] On Behalf Of Grant Youngman
Sent: Monday, March 14, 2005 2:32 PM
To: 'Discussion of AM Radio'
Subject: RE: [AMRadio] Xtal mike

Most any HI-Z mic will do.  You can use a crystal mic, you can use a dynamic
mic with an impedance step-up transformer, you can use most any mic with a
preamp, etc. 

Nothing magic about "crystal" per se.  As others have said, the D-104 can be
a good choice, but it is a buyer-beware situation.  The elements are
degraded by high heat and humidity, and eventually plain old age takes its
toll, and if that has happened the mic will sound thin and "tinny".  It's
hard to tell what you're getting if you buy one off the 150 deg F hood of a
pick'em-up truck at a 'fest (in fact, if you do that you have a high
probability of getting a bad element).  

Astatic/Omnitronics  no longer manufactures or supplies D-104 elements to
resellers, but apparently they still have new ones, and will (for a price)
replace them if you send them the mic.

Grant/NQ5T

> Excuse me...'senior moment'...I need one...anyone have one for sale?


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