Topband: How to measure the resonance of a tower?

DM4iM hamradio at
Tue Jan 18 14:02:22 PST 2011


R and J are:

Freq 1.820

R=54.6  jX=10.4 with dipole at operating height, connected to the system 
and tuned.

R=35.0  jX=-4.8 with dipole at operating height and disconnected at 
shack end.

R=16.2  jX=-35.6 with dipole disconnected and grounded.

No chance now to put down the dipole , it's 11 pm local.

Unmatching the dipole ( like setting the antenna tuner to a bad  match) 
doesn't change much.

Homing the elements of the SteppIR<>set to 20m also doesn't change much.

So the dipole has a big impact on the shunt fed tower.

Will remove the dipole tmw. and check again.
Any ideas how to detune the dipole?

Am 18.01.2011 22:19, schrieb W2XJ:
> You really need to be able to measure R and J. Move the shunt connection
> to establish the correct R and then tweak C to remove reactance. The
> flatness of the antenna will in part be determined by tower height and
> to a lesser extent the length and number of ground radials.


Martin DM4iM

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