[TowerTalk] Routing Ladder with Parallel Coax?

[Jim Lux]

On 4/5/14 11:43 PM, Tony wrote:
> All:
>
> My shacks location makes it difficult to keep ladder line away from
> other cables that enter the house. Someone suggested I use 2 runs of
> RG-11 coax in parallel to route the coax inside the house and then
> connect the two to the ladder line outside.
>
> The coax shields would connect to the tuner ground and the center
> conductors to the tuner output terminals. The shields are left open at
> the end where the coax center conductors connect to the ladder line.
>

this works, but the losses are higher than traditional window line. 
Mostly because the Z is lower (say, 100 ohms with two 50s or 150 ohms 
with two 75s), so the current is higher than with 450 or 600 ohm line. 
At HF, IR losses dominate over dielectric loss.

So you ask, why do you want to use a balanced line?  For a lot of 
people, it's because the loss is substantially lower, so you can put the 
tuner in the shack, where you can turn the knobs, and not get bitten by 
the mismatch.

If this is the case, then a 100 ohm doubled coax isn't going to get you 
where you want to be.


There's actually a dual 93 ohm coax out there (for IBM networking in 
decades gone by).