[TowerTalk] 75 or 70 Ohm twinlead or ladderline cable - does it exist?

[Jim Lux]

On 3/25/14 4:50 PM, Jim Brown wrote:
> On 3/25/2014 4:40 PM, Tom Osborne wrote:
>> I wonder if we are talking about the same 'twisted pair?'
>
> Probably not.
>
>> The wire I was talking about was the old telephone wire they had back
>> in the 50's and 60's that came from the pole to the house.  I think
>> most of it was probably number 12 or so copperweld wire.  It had a
>> funny insulation - almost like tarred rubber on some of it.
>
> I'm talking about twisted pair generally -- much of the world runs on
> twisted pair of one sort or another. Small signal audio typically uses
> #24 - #28, as does CAT5/6/7. Loudspeaker wiring in pro systems uses #10
> - #13, depending on the length of the runs. If I were feeding an antenna
> with twisted pair and didn't care about visibility, I'd use #10 for low
> loss. But if visibility was an issue (i.e., a stealth antenna), #22 with
> a good quality enamel would work for moderate power levels.
>

That makes sense.. the insulation thickness is probably the same, 
regardless of the wire diameter (within reason), because that's driven 
by mechanical ruggedness and voltage breakdown concerns... a 50 mil 
jacket over a 10AWG wire is very believable and would get you into that 
50-60 ohm range without too much trouble.