Fw: [TenTec] TWINCOM feedline ?????????????

[Robert & Linda McGraw K4TAX]

> I've seen various posts where 2 pieces of coax was used to run between the
> balanced output of a tuner and through walls and windows to get to a
> balanced feed line.  In general, this approach totally un-necessary and
I've
> found that it usually doesn't work very well either.  Should one find it
> necessary to run a balanced feed through a window, as long as the frame is
> not metal there is no problem.  Just run the line through and close the
> window.  However, in the case of a metal frame, I suggest using a couple
of
> 1/2" thick strips of adhesive backed weather strip, one on the bottom of
the
> window sash and one on the frame.  Run the feedline through and close the
> window.  Of course it won't close all the way so some concern and method
of
> security must be devised.  A stick propped from the top of the sash to the
> top of the frame prevents the window from being opened in a double hung
> window arrangement.  Same true where one has awing type windows, just put
a
> couple of strips of weather strip between the pane and the frame.
>
> For those that choose to use the twin coax method, by connecting the
shields
> together at the antenna feed point and again at the tuner end produces a
> "shorted turn" and yes, one will have trouble loading the arrangement.  It
> is strongly suggested that one connect shields at one end only if you
choose
> to use this method, ideally at the tuner end.  Be reminded that the loss
in
> coax goes up drastically with higher SWR values even at HF frequencies.
> This is the main reason for using "open wire" feed systems in a severe
> mis-match situation.  The dielectric loss is very low, even with high SWR
> values.  As to power handling abilities, since dielectric loss is low on
> open wire feed systems, the practical power limit is simply the IR loss of
> the conductors.  With coax operating with high SWR values, it must be
> de-rated in terms of power handling to account for heating due to
dielectric
> loss.  The heating is being generated by RF which is not
> radiated.........except as heat.
>
> I'm not sure about the true intrinsic value of the TITANEX feedline.
Looks
> expensive and not likely to work very well.
>
> 73
> Bob K4TAX
>
>
> ----- Original Message -----
> From: "George Osier" <gosier@twcny.rr.com>
> To: "Ten Tec Group" <TenTec@contesting.com>
> Sent: Monday, October 14, 2002 5:20 PM
> Subject: [TenTec] TWINCOM feedline ?????????????
>
>
> > Hello All !!!!!
> >
> > While looking thru antenna makers listed on the net I went to TITANEX
> > ........ Incredible antennas !!!!!
> >
> > But what caught my eye was TWINCOM feedline that looks like a
combination
> of
> > normal cord used for appliances and coax .................. 250 ohm but
> > similar in respects to ladder line ....... seems like it would be a good
> way
> > to get closer to the performance of ladder line ????????????
> >
> > Anyone ever use this stuff and what did you think ????????????
> >
> >
> > 73s
> >
> > George Osier , N2JNZ / QRP
> >
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