Twisted pairs are likely to be useful for wiring a control head 
further from the radio than the manufacturer-supplied cable, for the 
same reason we use them for other forms of data transfer.

I've used twisted pair wiring in audio applications for ages—it's a 
great way to eliminate interference.  Minimize ground loops directly 
bonding equipment, and use twisted pairs for audio signals.

At all costs, I avoid the overpriced junk they sell at hi-fi shops!  
Too many dissimilar metals, shields about as effective a piece of 
tissue paper, and silly notions like you can run 10 gauge wire into a 
solid 22 gauge pin connector with about 1mm of contact with a little 
spring clip and somehow improve the quality of your connection that 
way.  And lets not even begin to discuss the low-melt-point plastics 
they use and the cold solder joints you're going to wind up with to 
avoid turning your connectors into puddles.

Though you've got a point about using RJ-12 connectors.  Most every 
six conductor jack I've seen fits an RJ-45.  RJ-12 connectors might 
be required if that's what the jack will take.  As you say, typically 
RJ-12 cables are flat, but then so are typical RJ-11 cables between 
your wall and telephone.  IN the wall, though, if your home was built 
in the past 20 years, I'd guess you have at least six-strand cat-3 
twisted pairs to resist interference better.

In the past decade or so, more often than not, eight strand cat-5 
gets used by contractors, and even by telephone companies.  The phone 
doesn't require cat-5, certainly, and few residential systems need 
wiring for four lines!  It's just that today you can get spools of 
one for the same price as the other, and if you need only carry one 
spool of wire, it gives you more room in the van for other things.

I'm pleased to say my company was ahead of the curve on that one, but 
today it's pretty much standard practice.

Joseph - KF7QZC


On Sat, Sep 03, 2011 at 03:14:03PM -0600, colin McDonald wrote:
>but you can get six conducter cable with the six pin RJ12 jacks on
>it...they're not twisted pair, so if you have a need for six pin control
>jacks and six conducter control cable, you don't need to use cat5 or 8
>conducter cable.
>If you have a need for 8 conducter cable using RJ45 8 pin jacks, like for a
>microphone or something, then the twisted pairs in the cat5 aren't going to
>alter anything very much.  Twisted pairs become relevant when used for high
>speed data transfer, or telephone applications where impedance must be
>continuous down the cable.  For the tiny amount of signal passing through a
>mike extention cable, it would have absolutely no effect weather you were
>using part of a twisted pair or not for audio or PTT or up/down or fantom
>power or whatever.
>It's a totally different relm than networking or telecommunications, so the
>specifics of the cable are pretty much a moot point beyond how many actual
>conducters they contain.
>But you are right, one must insure that the pin outs match up at either
>end...and using a standard ether net cable, cat5, with RJ45's on each end
>will insure that you have a straight through pin to pin connection.
>With the kenwood radios, both the control cable, and the mike extension
>cable are straight through.  So, if you have cable that has pin to pin
>connection, like pin 1 on one end connects to pin 8 on the other end and so
>on, it'll work.
>If you have a cable that goes pin 1 to pin 1 and so on, it's not a straight
>through cable and will not work.
>
>73
>Colin, V A6BS
>----- Original Message -----
>From: "T. Joseph Carter" <[log in to unmask]>
>To: <[log in to unmask]>
>Sent: Saturday, September 03, 2011 6:04 AM
>Subject: Re: TM-V71A question
>
>
>> 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