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Old January 24th 06, 03:18 PM posted to rec.radio.amateur.antenna
dansawyeror
 
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Default 8405a working and measuring resonance?

Thanks. I have two coupler systems, one with very good directivity and one with
only moderate directivity. The antenna is resonant at about 141.6 MHz. There is
a difference of about a couple of hundred kc between the systems.

Now on the the "R" measurements. Both systems indicate an antenna resistance of
over 30 Ohms. This antenna has been modeled with three different models. They
all indicate a Rr in the range of 5 Ohms. The antenna is grounded by a 3 foot by
5 foot screen mesh. While this is not infinite, it should provide a good ground.
Do you have a suggestion of where to look for the discrepancy?

Dan

Frank wrote:
"dansawyeror" wrote in message
...

Frank, this is consistent with what I am observing. The claim is for a
given frequency when a 0j load (in the range of 10 to 40 Ohms) and an
unknown load (assumed to be in the range of 10 to 40 Ohms) show the same
phase shift then the unknown is 0j also. It is not necessary that the
loads be the same value, only within the range. (I will have to experiment
with loads over 60.)

So far nothing has surfaced to contradict this.

Thanks - Dan



Dan, essentially your assumptions are correct providing you have no error
terms such as poor directivity.

Frank