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Old July 6th 15, 04:22 PM posted to rec.radio.amateur.antenna
Wayne Wayne is offline
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First recorded activity by RadioBanter: Jul 2006
Posts: 409
Default An antenna question--43 ft vertical



"Jeff Liebermann" wrote in message
...

On Sun, 5 Jul 2015 17:08:56 -0700, "Wayne"
wrote:
I'm off on a different approach.
I have an RF ammeter mounted in a box. The box is in the shack between
the
ATU and the antenna.
I simply adjust the ATU for max current on the ammeter.


Rewind. I just noticed that you're planning to put the RF ammeter
between the ATU and the antenna. That will work, but with
approximately 1200 ohms antenna impedance, you are going to see
50/1200 = 0.04 times the antenna current that you would see on the 50
ohm line between the xmitter and the ATU. If you're running lots of
power, that might work, but offhand, methinks not.


Also, you can't adjust the ATU for maximum current. It adjusts itself
based on it's own internal VSWR sensor. All you can do is watch the
light show and listen to the relays clatter. You might be able to
have some control if it were a motorized antenna tuner. Certainly a
manual antenna tuner would work.


This isn't something planned. I have been using the ammeter between the
tuner and antenna for many years.

With an automatic tuner, there is no feedback from the ammeter to the tuner.
In that case it is simply an indicator that current is present.

Some of my antennas have SWR outside the capabilities of my automatic tuner.
A manual tuner is used in that case.

With a manual tuner, I don't look for a specific reading, just a peak in the
current from the tuner to the antenna.