wrote:

Here's what I'm doing and I'd like some feedback.

Antenna will be an 88ft doublet 30-40ft high supported at the center by
a ladderlock and fed by 450ohm windowline. The windowline will drop
down to within 8ft of the ground (above kiddie reach) where it will be
connected to a W2DU style choke balun based on RG213 and Palomar BA-8
ferrites. This will be enclosed in a ~12" length of electical conduit
which will be supported to relieve the windowline of further strain.

The coax will connect at the bottom of the choke enclosure via
PL259/SO239 to a ~10ft length of RG213 down to earth level driploop and
up into a small lockable mushroom enclosure containing a ICE300
supported on a 5/8"x8ft copper ground rod. Also contained in the
enclosure will be an LDG RT-11 tuner which will be mounted on the
backside of the ground rod from the ICE300. A small RG213 jumper will
connect the ICE and RT. The shell of the shielded DB-9 control line
will have a small braid to bond it to the ground mounting point as
well.

Assuming you are going to use this system on 20m, EZNEC says
the 10' piece coax will see 166-j960 ohms for an SWR in excess
of 100:1. Depending upon where the voltage antinodes are located
and how much power you are running, that may be enough to cause
arcing at the coax connectors.

Why not run the ladder-line all the way to the tuner? Hint: SGC
says not to tie transmission line to the outputs of their SG-230.
--
73, Cecil http://www.qsl.net/w5dxp


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Hi Cecil

Output power for my use will never exceed 100W, more typically 5W or
less. The RT-11 is only rated to 125W. But your caution on impedance is
just the sort of feedback I was looking for. I was considering running
the windowline all the way to the ground but was concerned about the
neighbors' kids getting their hands on it. My alternative was to run a
bit of conduit upwards to shelter the windowline until it was out of
reach, ~8ft. I was concerned however about how large such a PVC conduit
would need to be to avoid problems with the windowline. Would 2" be big
enough since its non-conducting?

tnx
jtm

Jim Miller wrote:
Hi Cecil

Output power for my use will never exceed 100W, more typically 5W or
less. The RT-11 is only rated to 125W. But your caution on impedance is
just the sort of feedback I was looking for. I was considering running
the windowline all the way to the ground but was concerned about the
neighbors' kids getting their hands on it.

Look at the bright side - you could teach them something about
the physics of RF. :-)

My alternative was to run a
bit of conduit upwards to shelter the windowline until it was out of
reach, ~8ft. I was concerned however about how large such a PVC conduit
would need to be to avoid problems with the windowline. Would 2" be big
enough since its non-conducting?

If the PVC is kept away from conductors, 2" should be just fine.
--
73, Cecil http://www.qsl.net/w5dxp

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