Hi Will -
The MFJ 259 suffers from RFI (BCI). Most likely the squirly behavior would have
been different at another time of the day. I have heard, but don't know for
sure,
that the newer 259B model inproves this situation with a higher-powered
oscillator. The 259 is VERY handy, and I use it a lot, however, when things
don't
seem to make sense, I check things with the rig at the several watt level.
Regards,
Ken, K6HPX
AA4NC@aol.com wrote:
> 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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