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).
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