[Elecraft] KAT1 (K1) & end-fed halfwave wire antenna

[Bob Fish]

Hi Mike,
Another option is to wind a transformer on a toroid with a 3:1 turns 
ratio which will give you a 9:1 impedance transformation. If your 
antenna has a high impedance,
which an end fed half wave will naturally have, the transformer will 
drop the impedance down into the range of your auto tuner. The other 
advantages of this are, on other bands where your antenna impedance is 
lower your impedance will still be matchable for your tuner. Also, if 
you ground the low end of the primary and the secondary windings of the 
transformer, it should make your antenna quieter in terms of noise.  I 
read somewhere that it makes your antenna less attractive to lightning 
by not having that positive static charge on it, but I am not sure about 
that part. I have an end fed half wave which I like, but I have a 
homebrew tuner.

73,

Bob  K6GGO


Mike Markowski wrote:
> The other day I posted an antenna question about making a K1 antenna 
> that avoids halfwave multiples (& thanks again to the guys who replied 
> offlist).  From the calculations in that note and some modeling by 
> another op it seems the ~18m/60' is probably the length to try there.
>
> But end-fed halfwave antennas have some advantages, especially the 
> fact that as a voltage fed antenna they have less of a need for a low 
> impedance ground to keep rf losses low.  On the other hand, they offer 
> very high impedance to the tuner.  The KAT1 manual says to look out 
> for "rf problems" at exact half wavelengths but doesn't come out and 
> say if it can or can't handle it (even if just at certain ranges of 
> length).
>
> A longtime ham told me some ATUs used to have a switch to move a cap 
> to one end of the matching network or another to offer a wider 
> matching range.  So if the KAT1 can handle the impedance, great.  If 
> not, maybe I can put a coil in series and tap it at the 50 Ohm point 
> of the coil. I'm not sure if it's worth the effort, especially since 
> it'd be nice to keep portable ops as simple as possible.  But if 
> there's a noticeable performace increase...  Has anyone tried either 
> method?  (That is, direct connection of halfwave end-fed or tapping an 
> inductor.)  Thanks for any ideas.
>
> 73,
> Mike  ab3ap
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