TopBand: z measurements

[W8AV@aol.com]

In a message dated 98-08-06 16:54:47 EDT, you write:

<< I used the following method to measure impedance of antenna: 
 (might be crude, and won't tell you reactances)
 
 I fired up transmitter at low power through the SWR bridge and antenna tuner
 on desired frequency into the antenna. Tune the tuner for 1:1 SWR. Disconnect
 the antenna and replace it with suitable (to handle TX power) resistor bank
or
 potentiometer (noninductive) and set the resistance to achieve 1:1 reading
 again.
 Take ohmmeter and measure resistance, this gives you equivalent impedance of
 antenna under question.
 Used this method to find out impedance of beverages and rhombics in days
 before antenna analyzers. Hope it helps.
  >>

Yuri has a pretty good idea. There is one problem though.  Using this method
you can only determine the resistance of the antenna under test.  You can not
get any idea of what the reactance in the system is.  By using an impedance
bridge you can determine both the resistance and reactance of the system.
.  When matching a 160 vertical for example. I try to get all the reactance
out of the system so that I have a purely resistive load to the
transmitter/amp.  But I am somewhat of a purist with these antennas since I do
it in the broadcast industry all the time. If you don't care about the
antenna's reactance and are just trying to get a 1:1 match, however, Yuri's
method will work very well.

73............................de Goose W8AV

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