Below are some hints from one of my past towertalk postings.
Dave Hachadorian, K6LL
Yuma, AZ
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2. Using an ohmmeter, measure the dc resistance from the
outer
shell of the 10 meter capacitor to the outer shell of the 15
meter capacitor on each element half. It should be less than
about 0.5 ohm if all connections are clean and tight
(Actually, I've seen M2 antennas with <0.1 ohm typical).
This one measurement tests every connection in the element
half. Remember to subtract the resistance of the ohmmeter
leads.
3. Here's a hint from Jim, N6IG:
"I realized that if you were to measure the DC
resistance between the element halves of the rear
driven element, you should see a DC loop along the
straps, out the front driven, up the matching bars
and through the balun coil."
4. Make sure that the phasing straps are not shorting
to each other or touching the boom or anything else,
with the antenna in the installed position. Make sure
the phasing straps are secure, and that the swr does not
undergo major changes when the straps are flexed with a
broomstick.
5. Try replacing the balun with another 4:1 balun, or try
putting a 200 ohm resistor across the balun, and seeing if
the swr on an analyzer comes out to 1.0 across the bands.
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