You're likely to get mixed results using standard network cables on 
something using six conductors even if the RJ-45 connectors fit.  The 
reason why should be obvious to a ham: Inside the cat-5 cable are 
twisted pairs which provide balanced transmission lines for the 8 
conductors (actually only 4 of them got used until the era of 
gigabit ethernet, but that's another story!)  In order to be able to 
use cat-5 to control any radio not wired for 8 conductor ethernet 
cables, you're going to need to connect the pairs appropriately.

If ethernet has wire pairs A, B, C, and D, with wire 1 being striped 
and wire 2 being solid, you get wiring like this:

1: A1
2: A2
3: B1
4: C2
5: C1
6: B2
7: D1
8: D2

Electrically, it doesn't matter which pair is which, or which wire is 
solid or striped so long as you match the wires on both ends with 
your continuity tester!  But there is a color standard, which we'll 
ignore for the sake of argument.  Pairs C and D are completely unused 
by 100Mbit ethernet, so you occasionally see power lines run that 
way, but I wouldn't suggest it on gigabit lines!  *grin*

Probably something using six conductors will take an RJ-45 connector, 
but will tend to only use the middle six contacts.  It's easy to see 
then that whatever signal happens to be passed on lines 2 and 7, 
using a regular ethernet cable, would be unbalanced.

Two likely possible wirings:

1: NC
2: A1
3: A2
4: B1
5: B2
6: C1
7: C2
8: NC

or more likely perhaps:

1: NC
2: A2
3: B1
4: C2
5: C1
6: B2
7: A1
8: NC

This is assuming straight connection.  Don't assume that!  Somewhere 
I had a brilliant little old-school phone wall plate that broke out 
an RJ-45 connector to 8 screw terminals.  Today, you'll find people 
mostly use keystone jacks and a punchdown tool, simply because doing 
so untwists very little wire, which helps avoid unbalancing your 
balanced lines!  Remember, we're talking at least 100Mbit/sec here, 
which means those twisted pairs are carrying VHF signals.  Moreover, 
the signals are bidirectional!

If you can find out your radio's control head pinout, it'd be much 
easier to wire a cable's pairs appropriately.  You'd be surprised how 
well a twisted pair of wires eliminates the need for a shield if you 
have the right signals running in the right pairs.  If not, shielded 
twisted pair does exist for industrial environments.

Joseph


On Fri, Sep 02, 2011 at 10:19:50PM -0500, Gary Smith wrote:
>Thanks to everyone who responded to my questions.  I'm not ready to put one
>in a vehicle yet but this info will help when I am.
>
>73, Gary-N5GD
>
>
>-----Original Message-----
>From: For blind ham radio operators [mailto:[log in to unmask]]
>On Behalf Of colin McDonald
>Sent: Friday, September 02, 2011 12:50 PM
>To: [log in to unmask]
>Subject: Re: TM-V71A question
>
>well if the control head cable is 6 pin, then you can't use cat5 because
>cat5 is 8 conducter, and RJ45's are 8 pin.
>You have to use that flat telephone or network type cable with 6 conducter,
>and the RJ12 six pin jack...which is the same size as the RJ45, but only has
>
>six pins instead of 8 on the plug.
>I would imagine you can probably find shielded 6 conducter cable though just
>
>like you can get shielded 8 conducter which is cat6.
>
>73
>Colin, V A6BS
>----- Original Message -----
>From: "Butch Bussen" <[log in to unmask]>
>To: <[log in to unmask]>
>Sent: Friday, September 02, 2011 8:53 AM
>Subject: Re: TM-V71A question
>
>
>> There have been mixed results using regular cat 5 cable.  Kenwoos uses 8
>> pin network cables, rj 45 I think.  Kenwood's over priced cable does have
>> the audio shielded.  The network cable is worth a try though.  The 71 uses
>> a rj 45 on the radio and a smaller, I think six pin on the control head.
>> You could possibly use the short pig tail that comes with the radio and
>> adapt to rj 45 cable.  The way Kenwood packages their stuff amazes me.
>> They actually make two kits, one has long power cord, long mike and
>> control cables but no mounting bracket.  Tlhe $50 one just has bracket and
>> control cable.  Go figure!!!
>>
>> 73
>> Butch
>> WA0VJR
>> Node 3148
>> Wallace, ks.