I cannot get the inverted L to provide a dip on my MFJ 259 analyzer anywhere
in the 160 meter band. I get dips at 8.2 MHz (R=36 ohms X=0) with reactance
on each side of X=0. At 5 MHz R=40 ohms X=0 with reactance on each side of
X=0. I cant get any significant dips neat the 80 or 160 band. However,
when I approach 1.750MHz the resistance drops to 6 ohms and X is off the
scale...at 1.825 I'm at 10 ohms and X is off the scale. Its as if my 140+
feet of wire is resonant on 8MHz.>>>>>>>>>>>>>>>
Given you have dips on 8.2 and 5 MHz, the MFJ is working normally.
With the tower so close to the Inverted L they are like one big coupled
system. I expect the "system" is resonant in the AM BCB, and that is why
you cannot find the low dip.
I would look for resonance around 5MHz / 3 and or at 8.2MHz /5 MHz. So look
around 1650 kHz or.
Another way to find the base frequency for Marconi resonance when a system
is out of band is to subtract the closest two dips and divide by two. (This
is what I use in the MFJ 259 firmware to find distance to fault.)
8.2 MHz - 5 MHz = 3.2
3.2 / 2 = 1.6
So you have two different methods pointing to 1.6 MHz as the resonance. This
tells me your combination antenna is on 1.6 MHz.
It might not move like you think because the tower is fixed at a certain
frequency, and probably well down in the BCB, but you can try making length
1.6/1.8 = .889 times what the L is now, or 129 ft. I wouldn't expect it to
move perfectly, but it should move.
***Ignore trying to determine resonance with a shunt wire. You are wasting
time, because that is a complex system. A shunt system consists of a
transmission line stub mode plus a common mode resonance, so you see the
combination of the two effects. It will NOT tell you where the tower is. ***
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