[Elecraft] Thanks! OT: Vertical doublets / baluns / tuners

Wed Mar 24 21:15:00 2004

For the most part, common zip cord insulation has ABSOLUTELY AWFUL
dielectric losses.

It may have a characteristic impedance as low as 25 ohms.

The velocity factor is utterly unpredictable, with no guarantee that
it's the same on both sides of the wire.

One 35 foot piece of the stuff I measured on 14 MHz had over SIX DB
return loss from a far end short, and its characteristic impedance
varied by ham band.

You have been WARNED about zip cord (read dummy load class) for
antennas and feedlines.

For field day stuff and especially QRP field day, stick with the tried
and true.

In a life or death emergency, if it's the only thing around use it.
Just don't ever PLAN to use it. There's always a better choice.

At one time one could purchase "kilowatt" 72 ohm twin lead. It turned
out that the stuff was just zip cord without the groove in it. Wasn't
good for more than 50 feet and that only on the low bands. That's why
you never hear about it any more.

73, Guy.

----- Original Message ----- 
From: "Joe - aa4nn" <[email protected]>
To: <[email protected]>
Sent: Wednesday, March 24, 2004 8:31 PM
Subject: Re: [Elecraft] Thanks! OT: Vertical doublets / baluns /
tuners

> Hi 'Crafters, I  have an experiment here with a doublet.
>
> Take 50ft of zip cord.  Split apart 22 ft to make the overall
horizontal
> length be 44 ft.  The remaining unsplit 28 feet is the vertical
parallel
> feedline to the shack.  Center height is 17 feet, two ends are at 10
feet,
> inverted "V".  I have a 12 inch stub of RG8X with 5 ferrite beads on
it.
> PL259 on one end of the stub and alligator clips on the other end.
I use
> the alligator clips to connect to the zip cord feedline and I attach
the
> PL259 to the KAT100 tuner.
>
> Now this KAT100 tries its best to tune, and on 10m through 40m it is
not
> bad.  But am I not missing something.  Wouldn't some kind of maybe a
4:1
> balun be needed to go between the balanced parallel feedline and the
> unbalanced tuner output.  ??
>
> I'm looking for a simple K2 Field Day setup.  Thanks.
>
> de Joe, aa4nn
>
>
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