Hi Will,
You probably experienced the effects of RF getting into the 259.
MFJ is releasing a "transparent filter" I designed that will cure virtually
all of these problems. Tests at some "unusable locations" have shown this
filter (patent pending) quite successful in eliminating problems.
All analyzers using broadband detectors (and that is every
amateur-radio-type-analyzer) are sensitive to the problem you saw. The
manual has a special section that warns you about these problems.
To test for this problem, put the 259B in the "Frequency Counter" mode and
connect the antenna. If the SWR meter indicates some SWR reading other than
1:1, your test location has this problem to some degree. Whatever SWR you
read during this test will be the lowest SWR the analyzer will read on a
perfect antenna.
> 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.
Another problem that occurs is balance. There can be cases where the
analyzer and shield to antenna connection path will upset some antennas.
Balanced antennas fed with coax sometimes require a good balun to prevent
this problem.
73 Tom
--
FAQ on WWW: http://www.contesting.com/towertalkfaq.html
Submissions: towertalk@contesting.com
Administrative requests: towertalk-REQUEST@contesting.com
Problems: owner-towertalk@contesting.com
Search: http://www.contesting.com/km9p/search.htm
|