Chris,

The problem with low cost analyzers is that they use broadband detector
diodes. Strong local AM radio stations will cause an output from these
diodes and generate erroneus results. In fact, MFJ suggests a highpass
filter before the instrument in order to alleviate this problem (in
areas with strong local AM stations). MFJ discusses this issue in the
MFJ-259B manual which is a free download @
http://www.mfjenterprises.com/manuals.php.

However, a German ham has modified his unit for operation from 40 kHz
to 1.8 mHz. This is not a trivial mod and it is described on page 88
of his manual @
http://www.darc.de/distrikte/f/27/MF...andbuch1v4.pdf

Unfortunately it is all in German so you will have to use Google to
translate the appropriate sections. BTW - this is the most
comprehensive user manual for this analyzer available anywhere.
Includes testing, calibration, schematic diagram, numerous mods,
operating tips and techniques, and how to build accessories.

Hope this helps - Roger