[TowerTalk] stub tuning

[Jim Jarvis]

Tom Osborne wondered why he was not seeing stub resonance
when the stub was installed in the antenna system.

-0-

Suggest you put a 50 ohm dummy load in place of the antenna,
and using a Tee connector to connect the stub, measure vswr looking at the
system,
at F and 2F, with the stub connected and disconnected.

You might also try measuring signal strength at F and 2F, using
the mfj 259B as a source...and a scope or meter w/RF probe, or
a receiver loosely coupled at the dummy load.  You should see the
attenuation.

In my private msg, I questioned the stub's purpose, which I assume
to be cutting 20m's second harmonic on 10.  Had I been more awake,
I would have observed that it doesn't matter. Simply look for changes
at F and 2F, whatever they are, as you connect or remove the stub.

If you want to be thorough, make measurements at F & 2F with steps out
to +/- 100KHz. Then, replace the dummy load with the real antenna system
and do it again.  You'll see shifts.

If you did this using your exciter as the source, on minimal power, it
would probably have more value.

n2ea
jimjarvis at ieee.org