I have a question about the low frequency accuracy of the MFJ 259 antenna
analyzer. I spent CQWW weekend doing some antenna work while KS4XG did a 15m
SOSB effort from here. Since the station was in use, I used my MFJ box to do
the testing on a 160m inverted vee I was building. I spent most of an
afternoon doing the up/down clip/add, etc. number and could never really get
the antenna in the ballpark according to the 259. The best I got was a 2.5:1
SWR dip at 1810 with the Z reading 125 ohms. The bandwidth was extremely
narrow. It went off scale on both sides within 20 Khz. I finally gave up on
the antenna, thinking there must be a bad connection or bad coax run.
After the contest was over, I had a chance to look at this antenna in the
shack. Two Autek WM1 wattmeters and the internal wattmeters in an FT990 and
IC736 showed the antenna to be quite resonant! The SWR curve looked reasonable
for an inv. vee with a 1:1 dip at 1830 and about 100 Khz bandwidth. I now
suspect that I wasted my time all afternoon - the antenna was probably fine as
originally installed. I was just being fooled by problems in the MFJ 259.
I haven't had the 259 very long, but until now it seemed to track quite
accurately with my other meters. I looked at some other antennas with it
today, and everything looked fine. It's just this 160 inv. vee that it can't
deal with.
Has anybody had any similar problems with their 259s ??
73,
Will AA4NC / W4MR
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