[Elecraft] K2, KAT2 and displaced choke balun feed

[Robie Elms]

Roelof,

I have used the arrangment you are asking about several times and it has 
worked well for me.  One key point is that baluns are not effective under 
some load conditions, usually when they are transforming high 
impedence/highly reactive loads.    So if you encounter problems matching 
the antenna on some bands you can "adjust" the load that the balun sees 
(from the antenna) by adding a short piece of transmission line between the 
balun and the antenna.  This technique uses transmission line properties to 
"transform" the impedence to a value that the balun is more capable of 
handling.  You may find that you need to add a piece to you transmission 
line on one or two bands.  The specific lengths depend on your specific 
installation.  The ARRL Antenna Book is a good place to learn about 
transmission line properties and how to use them.  There are many other 
sources of this information as well.

I hope this information helps.

Robie - AJ4F



----- Original Message ----- 
From: "Roelof Bakker" <roelof at ndb.demon.nl>
To: <Elecraft at mailman.qth.net>
Sent: Wednesday, August 15, 2007 8:44 AM
Subject: [Elecraft] K2, KAT2 and displaced choke balun feed


> Hello all,
>
> I have just finished K2 # 6177 and with all HF bands to my disposal, I am 
> looking for a more convenient way to feed my doublet wire antenna with 
> open feeder. My shack is in the dining room (my wife is very forgiving) 
> and the antenna feed-in is on the window sil at the opposite side of the 
> room. Hence I use 6 metre coax to get there.
>
> Has anyone tried a K2 and KAT2 fed into a substantial length of 50 ohm 
> coax
> with a choke balun mounted at the other end, connected to an open line
> feeder? So far I have used a manual balanced tuner on the window sil, but
> that implies getting up and walking to the tuner when changing bands.
>
> Thank you in advance,
>
> Roelof Bakker, pa0rdt
> G-QRP-C 6019
> QRP-ARCI 8405
> Middelburg, Netherlands
> JO11tm
>
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