MFJ MFJ-249, MFJ-259 Calibration Procedure Guide

MFJ

BOX APPEARANCE

1.

Check appearance of box in the following areas: a.
Missing or partly missing letters and numbers. b.
Scratches.
c. Deformed bends

d. Missing pin nuts

e.

Bad paint
f . Uneven cuts
g. SWR and Resistance indicators for correctness and scratc hes.
h. UTC 150 Counter Mo dule fo r scr a tches.

1. Check the following for tightness.
a. Seven (7) screws on the box face.
b. Six (6) screws on back
c. Four (4 ) scre ws o n back o f UTC 15 0 Co unte r Mo dule, (un der main c irc uit bo ar d)
d. Antenna S0239 bolts and nuts (2), and nuts on the two (2) "Input" & "Gate" push button

switches.
e. Knobs (Check for alignment, proper height, and tightness).
indicators bracket screws.

Check circuit board for the following:

a. Excess flux.

b. Bridge d so lder join ts.

c. Cold so lder join ts.

d. Loose wiring.

e. Ball t y pe s o ld er joints.

f . Unsolde re d jo ints .

2. Inspect Antenna jack and push button switches solder connectio ns.

of impressions

of

circuit bo ard.

Circuit Board inspection 1.

Tightn ess C hec k

f . SWR

& Resistance

Adjusting Counter Module.

1. Make sure unit is Off an d ins ert po wer plug int o powe r
jack. (Power = 12 vdc, Plug center is positive)

2. Set Frequency switch to 113 --170 range and tuner to maximum
clockwise position.

3. Turn unit on . D isp la y s ho u ld s how some frequenc y. Usually ar o u nd 17 0
to 174 MHz. Tough a hole in the back of the board adjust R32 until
display reads it h ighes t freq uenc y, (w ill v ary acco r ding to how L6 is
set).

4. Hook up an external frequency counter to the antenna jack.

5. Check to see if t he mod ule fre que nc y ma tc hes t he ex ter na l fre q ue ncy
counter fre que ncy . Mod ule fre que ncy s ho uld be stab le to w ithin .00 digits .

Setting the A.G.C. voltage.

pp

1.

Range switch should be in the 113 – 17 range.

2.

Tune disp lay to r ead 1 65 - 166 MH z.

3.

On back side of bo ard me asur e t he vo ltage o n p in 2 of ICI . It s ho uld be 300 - 4 00 mV.
Check voltage on p in 3 o f ICI and ad ju st R18 t ill vo lta ge matc hes pin 2 or is w ithin . 003 mV of it Volta ge o n

4

pin 3 shouldn' t drop belo w that of p in 2 because unit may bec ome unst able.

Setting Ranges

1. Set range 113 -170 b y adjusting L6. Yo u must spread or c lose L6 to o btain frequency. I deal
range would be: 112 -174 MHz.

2. Set range 62. 5 -1 13 by adjus tin g L5. Yo u mus t sprea d or c lose t he co ils on L 5 to obta in
frequency . I dea l fre que nc y wou ld be : 61 .8 - 114. 8 MH z.

3. Set range 26.2 - 62.5 by ad justin g L4. You must use a alignmen t tool for th is induc tor. Ideal
range would be: 25.5 - 63.25 MHz

4. Set range 10 - 26. 2 by adjust ing L3. Yo u mus t us e a a lign men t too l for th is in duc tor. I deal
range would be: 9. 97 - 27.0 0 MHz.

5. Set range 4 -10 by ad justin g L2. You m ust use a align ment to ol for
this induc tor. I dea l ran ge wo uld be : 3. 97 -10. 12 MHz

6. Set range 1.8 -4 by adjus ting L 1. You must use a a lignmen t tool for th is indu ctor.
Ideal range wou ld be: 1.76 - 4. 12 MH z

7. Recheck both top a nd botto m of all ra nges.
Note: When the back is put on the box all to p range s will dro p in freque ncy and also ba ttery lead placeme nt will
change fre que ncies due t o adde d ind ucta nce of the met al a nd w ire. If a ny do ubt, mark box wit h a st ick er and
have unit returned to you for inspection when back is put on. Each unit has a different spread in ranges. The
top of the ranges has the biggest drop when the back cover is put on.

SWR & Resis ta nce me ter s a djus tme nt

1. Set range switch to 1.8 - 4.00 MHz range. Plug a 100 ohm dummy load
into the antenna jack.

2. Adjust R17 for a "2" reading on the SWR meter. Exact reading should
be -. obta ined. Mete r s hou ld be s tab le.

3. Replace the 100 ohm dummy load with a 50 ohm dummy load.

4. Adjust R 31 till res is tanc e meter rea ds 50 o hms. Exact r ead ing s hou ld be
obtained. Me ter.s hould be s table .

5. Replace 50 ohm dummy load with the 100 ohm dummy load again and check
to see if resistance meter reads close to 100 ohms.

Note: The u

scale. Getting the 50 ohm reading when the 50 ohm load is in place is more important.

er scale of the resistance meter is less accurate then the lower end

of the

Checking "Input & Gates "

1. Check Input to unit by inputting a signal from another 2491259 Analyzer into the
Frequency Input BNC. Press input button till a "B" appears
in the upper right corner of the display module. This is the input mode and the display
should display the input frequency from the external frequency generator. Leave in the
mode for abo u t 15 se co nds to be s ure it does n' t fa de o ut or d is appe ar.

Warning: The frequency counter has a CMOS input device that can be easily dam aged. To

avoid dam age , obse rv e the fo llow ing :
Never exceed 5 vo lt s pe ak inp ut vo lt a ge.
Never input a signal with unit off.

2. Test "Gate " but to n to be s ure t hey c hange in or de r. The f ollo w ing s hould be dis pla yed as
button is de pr esse d; 0. 0 1, 0.1, 1.0 , 10. In th at or der. Make s ure they do n' t s kip or der .

Battery Leads Test

1. Place a short acro ss o ne of ba ttery co nnec tors.

2. Touch y our powe r p lug to the othe r b atter y co nne cto r by pla cin g the t ip of yo ur po wer plu g to
the large female socket and resting the outside contact of your power plug against the small
male con nec to r. U n it should come on.

3. Check other battery connector in the same manner.

Final Step

1. Turn unit po wer s wit ch off be for e sen ding to ba ck ins ta llat ion step.
Note: Wh iie no t re a l im p or ta nt , it 's goo d to leave the range switch and tuner in t he s ame position on each

unit. I place the range switch in the 113 - 170 position and the tuner fully clockwise, and power switch
off.