The SWR on the coax when you are using a 20m vertical on 40 would be
astronomical. I ran a quick EZNEC analysis of a 1/4 wave 20m vertical
with its base on the ground and got an impedance of 6.9 - j348. This
comes out to an SWR of about 187:1, which you would measure at the rig
as only 18:1 due to the massive 13.3 dB loss in the coax. 100 watts in
would give you something like 5 watts to the antenna.
Short answer: put the tuner at the base.
Of course, using a 20m antenna on 40 is about the worst case imaginable!
73,
Vic, 4X6GP
Rehovot, Israel
Formerly K2VCO
http://www.qsl.net/k2vco/
On 7 Aug 2016 05:58, rick jones via Elecraft wrote:
Ok sorry for not providing enough info! Consider this scenario: I
have a portable vertical with 4 counterpoise wires that is resonant
on 20. Lets say I want to tune the antenna up on 40. I can have a
tuner right at the base of the antenna OR I can just use a balun at
the base of the antenna and use the built in ATU in the K3. Is there
a difference in how much power is getting to the antenna? I assume
the tuner at the base is the best option which always makes me doubt
the usefulness of having an ATU built in to a rig in terms of getting
the most power to the antenna. Am I on the right track? Thanks! Rick
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