On 07/29/2011 05:14 AM, highlandham wrote:
Kenneth Scharf ,WA2MZE wrote :

The only window in my shack faces the front of the house. The window is
a a special hurricane resistant shatter proof glass. Also the window is
25 feet behind the location of the operating position in the shack room.
Access to the window is not possible, and the XYL won't hear about
feedline visible in the front of the house. I have a 2" plastic conduit
running from the operating position to the attic crawl space that
currently has on run of RG/8U for my vertical, with room for one or two
more runs. Running the twinlead next to the coax would probably not be a
good idea.
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Living in a bungalow ,hence having a ground floor shack ,I run DC cables
, 2 coax lines and twin feeder (450 Ohms ,the wide variety) all in the
same plastic duct (about 2 metres long) to the loft from where coax is
fed to an outside 2m beam and and a discone antenna (the latter used for
local 2m FM operations) and the twin feeder to a doublet (all fed
through a double cement block wall)
The 12 V DC cables run from solar charged batteries located on the loft.

With all those cables running through the same 2 metres long plastic
duct I don't experience any problems with RF operations with the twin
feeder.

BTW the plastic duct is a piece of square 65 x 65 mm gutter drain pipe
,widely used here in the UK.

Frank GM0CSZ / KN6WH
The two inch plastic conduit runs from the shack up through a wall into
the ceiling and into the attic. The overall length must be about 15-20
feet. There would be another 20 feet through the attic to reach the
vent turbine and the roof. The twinlead if it ran though the pipe and
the attic would probably twist many times. It might work, but it goes
against all 'textbook' logic.

In any event, I'm thinking of building the transmatch as a 'T' network
using the two 500pf 2kv variable caps and the roller coil. I will
insulate the bottom end of the roller coil from ground to leave the
option open of running the T match with a balum on the input side, but I
intend to try the coax choke on the far end of an unbalanced feed first.

As for the T match, it seems to be the sole surviver among transmatch
circuits. Both the 'ultimate' and the 'spc' are simply alternate forms
of the 'T' match that do not have any benefits.