[Elecraft] KAT100 with Ladder Line

[w2bvh]

I've been using Cecil Moore's (W6RCA)  "No-Tuner" with 450 ohm ladder 
line for about 7 years along with a K2 / KAT-2 and it has been a 
pleasure to use and pretty effective.

It's basically a box of 5 4pdt relays out in the yard that switches 
in/out combinations of 16, 8, 4, 2 and 1 foot lengths of 450 ohm ladder 
line to the main 450 ohm feedline to get a close match in the shack, and 
the KAT2 does the rest. The input to the relay box is fed with RG8X with 
a bead balun on the coax right at the box input.  The idea is to switch 
just enough extra line in to get a current antinode at the antenna 
feedpoint for the frequency of operation. For a 80 meter half wave 
antenna (with 10 meter fan element tacked on), the main 450 ohm feedline 
is about 85-90 feet long. I've worked/confirmed ~140 countries using 
this antenna with 12 watts or less (mostly 5 watts). And I'm not much of 
a dx fanatic.

73,
Lenny W2BVH




Geoffrey Mackenzie-Kennedy wrote:
> On Thursday, November 15, 2007 at 7:00 PM, Goody K3NG wrote:
>
>> Using any balun with an unbalanced tuner to feed balanced line can be 
>> bad news (your mileage may vary, standard disclaimers apply).  Under 
>> highly reactive loads, a balun used like this can become quite 
>> lossy.  There's a couple articles in publications and on the Internet 
>> on this, but Cebik's article is one that comes to mind ( 
>> http://www.cebik.com/link/l-bal.html ).  It's better to run a real 
>> balanced tuner like a Johnson Matchbox, the MFJ Balanced Line tuner, 
>> or others, if you can.
>
> ---------------------------------------------------------
>
> Well put Sir!
>
> As a comment to the List, the usual type of cored current balun 
> presented with a reactive load might appear not to be introducing loss 
> because QSOs can be made, but as the members of our QRP fraternity 
> well know contacts both 'local' and DX can be made using very low 
> power given the right propagation conditions. Proof of this loss can 
> be had by increasing Tx power up to the power rating of the balun at 
> which point the balun could well explode if it has not already at a 
> lower power, it will certainly becomes hot to touch. As K3NG says your 
> mileage might vary because the antenna's feedpoint impedance as 
> transformed by your feeder and seen by the balun might by happy fluke 
> be non-reactive, feeder length and feeder impedance are factors, 
> leaving only the R to deal with. If R turns out to be 200 ohms, then a 
> 1:4 balun would work well with a Tx which wants to see a load of 50 +j0.
>
> FWIW I agree with K3NG that the classic balanced tuner such as used in 
> the Matchbox is the best system to use when feeding a balanced line, 
> good efficiency and versatile.
>
> 73,
> Geoff
> GM4ESD
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