From kd7jyk at earthlink.net Thu Nov 26 02:33:44 2015 From: kd7jyk at earthlink.net (KD7JYK DM09) Date: Wed, 25 Nov 2015 23:33:44 -0800 Subject: [MFJ-Ameritron] Test. References: <000901cc3418$db18b230$2f01a8c0@HOMEPC> Message-ID: Last message I have through the group is dated: "Sunday, June 26, 2011 12:25" Kurt From kd7jyk at earthlink.net Sun Nov 29 23:33:09 2015 From: kd7jyk at earthlink.net (KD7JYK DM09) Date: Sun, 29 Nov 2015 20:33:09 -0800 Subject: [MFJ-Ameritron] MFJ-249 Modifications. References: <000901cc3418$db18b230$2f01a8c0@HOMEPC> Message-ID: 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