[MFJ-Ameritron] MFJ-249 Modifications.

[KD7JYK DM09]

I've been looking at the modification for the MFJ-249 antenna analyzer shown
on the following page:

http://njdtechnologies.net/modifying-an-mfj-259b-antenna-analyzer-to-operate-on-630-meters/

I opened up my MFJ-249 antenna analyzer today to get an idea of what it does
and how.  I also found a .pdf file of the manual and a relatively poor
quality- but good enough, schematic.

It's pretty straight forward.  The oscillator is a free-running L/C network
covering six bands, inductors ranging from a single turn of tinned wire to
four slug tuned inductors of varying value.

Frequency readout is via a counter covering a few Hz (according to the
manual) to about 200 MHz.  Band selection is by a six-position switch, the
inductors are easy to see.  The tunable inductors are easy to get to
without taking the unit apart, just take the back cover off.

I didn't have a tuning tool so I didn't diddle the oscillator to see what it
was capable of without modification.  I bought four diddle sticks today.

I didn't look too closely for placement of a switch for the inductor mod,
but I'm thinking on top of the unit with the other controls fed with RG-174.
I find the 249 fussy so I think it'd be wise to shield the leads.

While I'm at it...  Each time I use my analyzer, I screw an Archer 5W dummy
load to the top and sweep the band in question looking for a flat response
before connecting to the device under test.  I'm thinking of adding a
"Calibrate" switch with a precision non-inductive 50 Ohm resistor as well!

Thoughts?

Kurt