[Elecraft] KAT500 update

[Don Wilhelm]

Ron,

Yes, that is valid justification for putting the balun at the tuner 
input, BUT it ignores the physics of the tuner itself.  If the tuner is 
actually a balanced design, I have no problem, but many try to force fit 
an unbalanced tuner design after the balun.  That latter part is the 
part that does not fit.  There is no way that an unbalanced network no 
matter how well isolated can preserve the balance - just consider the 
phase of the signal as it passes through each tuner element if you want 
proof.

If you want to use a balun at the tuner input, then please follow it 
with a balanced tuner t maintain that balance.

If you want to use the "rule of thumb" that the balun impedance should 
be 10 times the load impedance, then refer to K9AY's RFI and balun 
information and use those 5 or 6 large cores to provide the proper 
choking impedance for up to 500 ohms antenna impedance (5000 ohms 
impedance for the balun).

73,
Don W3FPR


On 12/8/2011 7:36 PM, Ron D'Eau Claire wrote:
> Is it true that the efficiency of a balun is not affected by the impedance
> of the line in which it is used?
>
> The justification I had seen for putting the balun at the tuner input where
> it will see a load very close to 50 ohms resistive (when the tuner is
> adjusted for a "match") while at the output the balun may see anything over
> a huge range of impedances.
>
> Ron AC7AC
>
>