Vic K2VCO wrote:
There is no difference if the balun is on the input or output side of an
unbalanced tuner. See
That's only true of an ideal balun. A real current balun has a finite
common mode impedance, which is typically designed to be about 10 times
the nominal operating impedance. If you put it between the ATU and the
antenna, it will be working into the actual antenna impedance, which off
resonance will quite high and reactive. Under those circumstances, the
ratio between the common mode and differential mode paths may not be
very large.
I assume that you are using the balun because the antenna is balanced.
If not, just use the KAT2 directly.
The requirement that I'm trying to meet is that the K2 chassis not be RF
hot and that, if I connect the mains ground, there is no significant RF
in that ground. RF choking the ground has the same problem that the
choke impedance will not be large compared with an off resonant antenna.
That requires driving an antenna that is, at least approximately,
balanced - in reality it's not possible for me to get true balance,
because the antenna has to be indoors.
A choked earth doesn't remove the need for something to carry the return
current, and whilst it may get called an artificial earth, it is really
part of a semi-balanced antenna, and unless it is massive compared with
the "antenna", will probably be more balanced that unbalanced.
internal tuner to find a match. I then added some capacitors in series
with the feeders to cancel the reactance. I used a compromise value
In other words, you added a balanced tuner on the antenna side of the
balun! I'll accept that there may be solutions that do coarse tuning on
the antenna side, to get the impedance into the right ball park, then
use the unbalanced tuner, on the equipment side, to do the fine tuning,
but what you are describing is still doing a lot of the tuning antenna side.
--
David Woolley
Emails are not formal business letters, whatever businesses may want.
RFC1855 says there should be an address here, but, in a world of spam,
that is no longer good advice, as archive address hiding may not work.
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