"J. C. Mc Laughlin" wrote in message
...
Dear Mikek (no call sign):
Assuming that the inductor is 3 +j310 because it must have some loss and
calling the capacitor -j717, my trusty calculator estimates the antenna
looks like 159 -j526. The real part seems high - probably due to ground
losses.
From what I have read it seems very high, could I have 130 ohms of ground
loss?
I don't think so.
I'll be looking into the ground, I think it is just a 6 foot rod, I put it
in years ago.
I'll add FWIW, I connected the AC ground from a receptacle and it made zero
change.
However, the idea that even such a simple an antenna can be modeled as an
R and C over the AM broadcast frequency range seems unlikely.
Ya, that's not the plan, I'll check it every 100 khz and make a graph, with
R and C.
An instrument such as the AIM4170C would provide Z with greater confidence
and do so at each frequency of interest. However, in the broadcast band
it is not clear that such a set of impedances can be used for something
useful. What is the actual goal?
I put the antenna up for multiple use, but to start, I want to use it with a
crystal radio,
the measurements may help me figure out the series cap (range) needed to
make an
R match to the tank circuit over the band.
And it's a project that forces me learn some math.
Thanks, Mikek
Regards, Mac
"amdx" wrote in message ...
I put up a long wire antenna, it is an inverted C.
The antenna is resonant at 3.55 Mhz.
I want to characterize it an the AM broadcast band.
I have made a measurement at 500 Khz and I had to install a parallel
capacitor
to get my variable inductor to bring phase to zero.
I don't know how to do the math to find the impedance of the antenna
with the L and C in the circuit.
Can someone look at my drawing and give me the math so I can figure out
the impedance. Then I can get the numbers at other frequencies for the
band
and calculate those impedances.
See drawing here. I want to calculate the Unknown Impedance.
I need the R and the C of the antenna.
http://i395.photobucket.com/albums/p...naat500Khz.jpg
Thank you, Mikek
J. C. Mc Laughlin
Michigan U.S.A.
Home: