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K4RKY
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.

W9GB
05-02-2007, 07:53 PM
First, get a copy of your Kenwood TM-271A owner's manual -- this will have the pin assignments for your microphone connector.
http://www.kenwoodusa.com/product....pr=2235 (http://www.kenwoodusa.com/products/ListProduct.aspx?k1=3&k2=9&k3=10&pr=2235)

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.
http://bama.edebris.com/manuals/astatic/d104

http://www.circuitcellar.com/library/print/1001/nisley135/index.asp

http://members.cox.net/n4jk/d104.htm

http://members.aol.com/tcsopr/d104mic.htm
Restorations
http://k9toa.net/id12.html

BTW, the low audio of the TM-271A is very well documented on the Internet.

K4RKY
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.

W9GB
05-04-2007, 01:17 PM
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!
http://www.barovelli.com/radio/astatic/astatic.htm

Parts listing for D-104 micrphones
http://www.rrcom.com/pictures/astatic/partsforbasemic.html

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).

w9gb

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