View Full Version : Microphone Wiring
05-02-2007, 07:40 PM
Could anyone help with a mic wiring issue? I have look all over the net and do not see a wiring diagram that would allow me to wire a D-104 to a Kenwood TM-271A radio. Any suggetions or maybe point me in the right direction? Thanks.
First, get a copy of your Kenwood TM-271A owner's manual -- this will have the pin assignments for your microphone connector.
Second, idenifty which D104 base you have - Astatic made this microphone model for almost 70 years! #
The D104 model uses a crystal or ceramic microphone element. #The D-104 "crystal" element -- it is very sensitive to heat, shock (vibration) and abuse -- which can cause failure of the element. #This is often why they are readily available - as "not working" from ex-CB operators.
Replacement crystal elements from Japan by Kobitone (Mouser) are readily available.
Crystal elements are Hi-Z (~ 50Kohms) -- BUT modern solid-state transceivers are Lo-Z (~ 600 ohm). #Matching is required for suitable operation - this can be accomplished with a transformer OR the Astatic pre-amp base.
BTW, the low audio of the TM-271A is very well documented on the Internet.
05-03-2007, 02:20 PM
Lessons learned! I have the D-104 (lollipop) on the tug-8 base. Thanks for the help. All I had to do was add a short peice of cat-5 wire to each mic wire so it would fit in the modular plug. Works great but I have to keep the gain low (about 25%) to prevent overmodding.
Yes, sounds like too much gain from your TUG_8 pre-amp (in base of Astatic).
That pre-amp does have a volume control !
BOOKMARK these WEB PAGES!
Parts listing for D-104 micrphones
That pre-amp also handles the Hi-Z (Astatic D-104 crystal element) to Lo-Z (Kenwood mic input) matching for you.
ALSO, by using category 5 UTP your cable is not shielded -- which may cause problems with stray RF getting into your audio chain (D-104 pre-amp, radio audio stage).