[aprssig] D700 microphone cable

Stephen H. Smith WA8LMF2 at aol.com
Thu Aug 26 23:24:33 EDT 2004

Chuck Gooden wrote on 8/26/2004, 8:50 PM:

 > I am considering using a CAT5 network cable and
 > an RJ45 line coupler to mount the microphone up on the dash.  Has
 > anyone done this? Were there any problems?
 > Is the connector on the microphone for the D700 an RJ45
 > connector?  Will ferrite cores be necessary on each end?

Yes it is an RJ45 connector.  The problem is that most CAT5 cables 
aren't shielded (in the U.S. at least -- I hear shielded CAT5 is common 
in Europe).    I made an shielded "extension cord" for my D700 mic by 
getting a surface-mount female RJ45 jack (the kind in a square beige 
housing that screws or sticks to the wall with an adhesive pad)intended 
to place LAN outlets near desks.

This type of jack normally has color-coded internal punchdown terminals 
for the individual conductors of the CAT5 cable.  Crimp a normal 8-cond 
plug on the end of the cable going into the radio.   Before you punch 
down the conductors at the other (jack) end of the cable, slip a piece 
of braided outer conductor removed from RG58 coax over the outside of 
the cable.

[ You can get the outer-conductor braid off coax very easily by slitting 
the black outer jacket lengthwise with an X-acto knife and peeling it 
off.  Then push the braid together from each end. The shield braid 
diameter will increase slightly and slide right off the center conductor 
and insulation very neatly. ]

Attach a short pigtail with a small ring terminal to the braid at the 
radio end and ground it to the radio chassis (one of the locking nuts on 
the D700 DB9 serial port is a convenient place to grab ground -- 
sandwich the ring terminal between the DB9 plug (if used) and the 

Verify that the cable is wired straight through; i.e. pin 1 at one end 
is pin 1 at the other.  If you follow the standard LAN cable color 
coding standards for crimping plugs, this should happen automatically.

When you are finished, you can plug the D700 mic into the jack of this 
"extension cord" and plug the other end into the radio mic jack.

Stephen H. Smith                   wa8lmf (at) aol.com

Home Page:                            http://wa8lmf.com

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