[Elecraft] Antenna Question for KX1

[Trevor Day]

In message <20060429224957.E1F31859C1C at mailman.qth.net>, Paul Webb 
<m0bmn at yahoo.co.uk> writes
>Hi All
>
>
>
>I have been playing with my KX1 in the back yard the last week or so and
>found that about 26ft of wire in the hot side of the bnc connector and about
>the same to the cold side gets me a good match with the built in ATU on
>40,30,20m
>
>Now if I use the same wires but add 20ft of coax between the radio and these
>wires I find it very hard to get a match on any band, do I need to use a
>balun at the end of the coax?
>
>Any thoughts
>
>Paul

Hi Paul,
I believe you are on a hiding to nothing attempting to reproduce the 
results via a length of coax cable.  Remember those initial results were 
obtained with the ATU connected directly to the antenna.  Everything 
after the ATU is effectively the antenna and is likely to radiate, 
including the coax. Adding a balun will do absolutely nothing except to 
change the electrical antenna length (where the antenna in this case is 
the coax and the original wires), your coax will still radiate and you 
are likely to get poor results.

With this sort of antenna the ATU must *always* be at the antenna end of 
the feeder, whether that be directly after the ATU in the KX1 as in your 
initial trials, or at the antenna end of the 20 foot of coax as you 
attempted later.  The only exception to this is when the antenna 
presents an electrical quarter wave or odd multiple thereof.  In those 
cases, no ATU is necessary.

Trev G3ZYY

-- 
Trevor Day
UKSMG #217
www.uksmg.org