[TenTec] 450 ohm Feed Line - N5BEA

Wed Apr 14 22:02:30 EDT 2004

I have used one of the "ladder lock" devices for several years and quite
successfully I might add.  I do support the center of the 256 ft center fed
wire with a wooden arm from the top of the 60 ft. tower.  I seem to recall
it is a piece of 2 x 4 pressure treated material with a pair of suitable SS
U bolts and SS eye hook.   It stands the center support off of the tower
some 18".   The feed line is supported via 18" pieces of 3/4" PVC.  Cut a
slot about 1.5" deep in one end, drill a 3/16" hole about 3/8" from the end,
slide the feed line in the slot.  I use a machine screw to squeeze the slot
tight.  The PVC is attached to the tower leg via a suitable U bolt at the
other end.  I space these stand-offs about every 10 ft down the tower.    I
do twist the feed line some 4 to 6 turns in between the stand offs to
minimize wind whipping and twisting.  Plus it assists in maintaining balance
in the antenna system.  All of this has been in the air, wind and weather
for some 7 years now at the present QTH without a failure or replacement of
any parts.

The feed line exits the tower via a home made spark arrestor made from a
pair of Champion small engine spark plugs mounted on a metal plate which is
attached to the tower leg via a SS U bolt.  It then enters the house via a
wooden opening in the gable, is swung from the wooden roof rafters with some
home made PVC stand offs, to the point it drops through the ceiling behind
the tuner and operating position.  Again, I twist the feed line in between
the supports in the attic.

I use a high power 1:1 current balun, external to the Tentec 238 tuner.  I
run legal limit, all bands 160M - 10M, all modes with out any problems,
meaning no telephone, TVI or RFI anywhere in the house.  And yes, the TV
antenna is side mounted on the same tower some 20 feet from the top.  The
nearest VHF TV stations are 65+ miles away.

I have found that 4:1 baluns can cause some difficult Z matching issues
under certain circumstances.  I don't advise using 4:1 baluns unless one
needs the Z step up values.

All of this works for me and has in several locations over the past 45+
years.

73
Bob, K4TAX

----- Original Message -----
From: "Jason Buchanan" <jsb at digistar.com>
To: <tentec at contesting.com>
Sent: Wednesday, April 14, 2004 8:06 PM
Subject: Re: [TenTec] 450 ohm Feed Line - N5BEA

> ac5e at comcast.net wrote:
>
> I am thinking about getting one of these gizmos to make life simple:
>
> http://radio-ware.com/llock.htm
>
> But regardless of what I use to tie the antenna wire to the ladder line,
> am I going to get myself into trouble if I tie the center feedpoint of
> the antenna to my metal mast?  I plan to use a 2 foot plastic standoff
> along the entire length of the mast to hold the ladder line away from
> the metal mast but at the very top of the pole I will need to secure the
> dipole to something very strong to support 260 feet of wire and I'm
> wondering how much of a problem this is if it's secured near the mast,
> or directly to it at that one point...
>
> > One note. There is a misapprehension that ladder line either won't
radiate or it won't radiate (or pick up noise) if it has a 180 degree twist
every 10 feet or so. Let me state unequivocally that any sort of twin lead
will radiate, the wider the spacing between the wires the more it will
radiate, and anything that unbalances the line will increase the amount of
radiation. Twisting the wire MAY result in cancellation - and it MAY reduce
the amount of noise pickup. But it's likely to have no effect at all.
>
> How much danger is there if I bring the ladder line through the wall of
> the house, along the ceiling of the garage (which is the 2nd story
> floor) and into the shack?  The shack is roughly in the middle of my
> house on the ground floor.  The ladder line will have to traverse at
> least 30 feet from the outside of the house to the inside to reach the
> shack.
>
> Am I going to spew RF all over the inside of the house as the ladder
> line leaves the back of the tuner in the shack, through the garage
> (which is underneath a bedroom because there is a bedroom above the
> garage) and then outside?
>
>
>
> Thanks!!
>
> 73 Jason N1SU
>
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