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MFJ-259 Antenna Analyzer Calibration

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Tony Fegan VE3QF

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Oct 19, 1998, 3:00:00 AM10/19/98
to
I have an MFJ-259 which is a few years old. When terminated with a 50
ohm non-inductive load, the resistance scale reads 30 ohms. The no load
reading is 200 ohms and the short circuit reading is 0 ohms. SWR readings
are quite accurate.
Does anyone have alignment info? I have E-mailed MFJ but so far no
reply. I am doing a demo in a couple of days and would like to fix it before
then.

Thanks for any help, 73

Tony Fegan VE3QF
ve...@amsat.org

AMDX

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Oct 19, 1998, 3:00:00 AM10/19/98
to
Hi Tony,

The Resistance adjustment pot. is R31. I know, you can't see the
pot labeling unless you take it all apart. So, R31 is connected between
pin 7 of the IC. and a 4 pin connector.
I've heard MFJ calibrates a 4 Mhz, If you make your 50 ohm resistor
connections very tight that's probably ok. Try it and then see what
your resistor measures at 1.8Mhz.
BTW, R7 is for SWR it's connected to pin 8 of the IC.
R18 is the output signal level adjustment.
R35 is the input level to the freq. counter.
Let me know if you need more info.
Mike


Richard Earl

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Oct 19, 1998, 3:00:00 AM10/19/98
to Tony Fegan VE3QF
Hi Tony,

Have you tried to measure your "50 ohm non-inductive load" with an
accurate ohm meter other than the MFJ?

perhaps your load is not 50 ohms!

73

Rich

W9JUC

John DeGood

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Oct 20, 1998, 3:00:00 AM10/20/98
to
> I have an MFJ-259 which is a few years old. When terminated with a 50
> ohm non-inductive load, the resistance scale reads 30 ohms. The no load
> reading is 200 ohms and the short circuit reading is 0 ohms. SWR readings
> are quite accurate.

My MFJ-259 developed similar symptoms shortly after I bought it. I
sent it back for warranty repair and the paperwork said they replaced
2 diodes.

It is unfortunate that MFJ doesn't provide schematics!

73, John NU3E

Sean

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Oct 21, 1998, 3:00:00 AM10/21/98
to
Mine 259 reads low on impedance after a few years worth of use
also. I contacted MFJ at Dayton and they sent me the necessary
paperwork to correct it. Where it went to from there, I can't
recall. I have spoke to a few other guys that have them and it
isn't uncommon. Sean.
>
Tony Fegan VE3QF wrote in message
<7%xW1.10369$Ig6.3...@news.rdc1.on.wave.home.com>...

> I have an MFJ-259 which is a few years old. When terminated
with a 50
>ohm non-inductive load, the resistance scale reads 30 ohms. The
no load
>reading is 200 ohms and the short circuit reading is 0 ohms. SWR
readings
>are quite accurate.
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