[Elecraft] K2 KAT100 and BL2 questions

[Don Wilhelm]

Brian,

That antenna is commonly referred to as "two half waves in phase" and 
has 2 to 3 dB gain broadside to the radiator.

Yes, its feed impedance is high, but if the feedline is somewhere near a 
quarterwave (or odd multiple thereof) long at the frequency of interest, 
the feedline impedance at the shack end will be low.

A bit of 'playing' with a program like TLW (download for ARRL website) 
will indicate what the feedpoint impedance at the shack end might be for 
the various bands of interest.

The KAT100 matching range does not usually favor extremely high 
impedances, and because the 'delta LC' is fixed, the matching range will 
be greater on higher bands than lower ones.  To completely answer your 
question, we would need to know the length and type of your feedline and 
the band of operation - but I believe I have included enough information 
that you can now figure it out for yourself.

73,
Don W3FPR

Brian Lloyd wrote:
> Does anyone know if the KAT100 has enough range to match a radiator 
> that is close to (or is) an end-fed 1/2 wave? What I am thinking about 
> is feeding a dipole at twice its resonant frequency so that it is 
> effectively two end-fed  1/2 wave sections and then feeding with 
> ladder line. Now the ladder line will probably act as a transformer to 
> change the matching equation. (I know it won't change the SWR but the 
> magnitude of the resistance and reactance components will change.)
>
> This also brings up a question I asked much earlier but didn't get a 
> good answer to. Will the Elecraft BL2 4:1 balun intended for 300/75 
> ohm operation still work properly when feeding the equivalent of two 
> end-fed half-wave antennas? If I recall these would represent about an 
> 8000 ohm impedance. I was thinking of locating the balun very near the 
> tuner and using window line to the doublet. I am concerned about 
> losses and arcing (100W) in the balun in that specific instance.
>
> -- 
>
> 73 de Brian, WB6RQN
> Brian Lloyd - brian HYPHEN wb6rqn AT lloyd DOT com
>
>
>
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