MFJ MFJ-864 User Manual

MFJ-862 SWR/Wattmeter

MFJ-864 HF/144/440 SWR/Wattmeter



General Information:

The

MFJ-864

power and indicates SW R for the
The MFJ-864 has 2 power scales f or each band s elected with the front panel
rotary switch. The low power scale reads f rom

watts reflected
watts reflected

HF/144/440 SWR/Wattmeter measures forward and reflected

1.8 - 60, 144

. The high power reads from
. SWR is indicated from

1:1

to

, and

440 MHz

0-30 watts forw ard

0-300 watts forw ard

.

5:1

ham bands.

and

0-6

and

0-60

MFJ-864 Theory of Operation:

The MFJ-864 senses RF energy traveling along a 50 ohm stripline. A
forward and reflected stripline couple to the 50 ohm stripline to make a
directional coupler. A voltage is produced in the forward and reflected
striplines that is proportional to the current and voltage traveling along the 50
ohm stripline. This signal is rectified by a diode and smoothed by a capacitor.
Because the directional coupler's sensitivity increases with frequency,
trimpots are used to adjust for different frequency and power settings (high or
low power).

Connections:

Connect your HF transmitter and antenna to the
connectors labeled
VHF/UHF transmitter and antenna to the
connectors labeled

important that you use good quality coax and connectors that are
designed for HF and VHF/UHF!

TRANSMITTER

XMTR

and

on the rear panel. Connect your

ANT

144 / 440 MHz VHF/UHF Sensor

and

ANTENNA

1.8 - 60 MHz HF Sensor

on the rear panel.

It is

If you want to measure the power c apability of a transm itter/am plifier or to re­calibrate the MFJ-864 you should connect a quality dummy load (50 ohm s)
that is designed for VHF/UHF to the antenna jack.

1

MFJ-862 SWR/Wattmeter

F

I

F

I

The MFJ-864 has a lighted m eter. To pr ovide power for the meter light, a 12
Vdc supply such as the MFJ-1312B should be used. Use a standar d 2.1 mm
coaxial plug with the center conductor positive and the sleeve ground.

Using the MFJ-864:

To measure forward and reflected power turn the selector switch to the
correct frequency and power setting. Transm it and read the power from the
meter. Each unmar ked hatch on the scale is an even division between the
two marked num bers. SW R is read directly from the sc ale where the meter
needles cross.

If a more exact reading for SW R is needed you may use the equation for
SWR. Measur e the forward and reflected power and put the values into the
following equation:

SWR = 1 +

Pr = Reflected Power

Calibration:

Note that the readings for forward and reflected power (and thus SW R) are
less accurate if the power levels you are reading are not near the calibration
power level or within the correc t power range. For an acc urate reading of 10
watts forward use the low power scale. If your transmitter only transmits 10
watts, re-calibrate the low power scale at 10 watts for maximum accuracy.

The MFJ-864 has been calibrated at the factory for 10 and 100 watts. If re­calibration is necess ary you will need a 50 ohm dum my load, good quality 50
ohm coax, and a transm itter of known power or another accurate wattmeter
to use as a standard.

Connect the transmitter to the
of coax between the
a known power level and adjus t the f o rward or r ef lec ted sens itivity pot, for the
power scale and frequenc y you are using, until the correct r eading is shown
on the meter.

G

H

Pf = Forward Power

TRANSMITTER

ANTENNA

Pr

J

Pf

K

connector and a good length

connector and the dumm y load. Transmit at

1-

G

H

Pr
Pf

J

K

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MFJ-862 SWR/Wattmeter

Meter Calibration

If the zero adjustment of your wattmeter should ever need to be re-adjusted,
it is a simple procedure. T he meter should be re-zeroed whenever a pointer
is more than 2 pointer widths from the "0" mark.

To re-zero the pointer, first you must remove the meter from the chassis.
Remove the screws from the meter tabs from either the front or the ins ide of
the unit. Next carefully remove the
clear plastic front by grasping it on both
sides.

Use a pair of needle nose pliers to turn
the zero adjustment lever. Turn
clockwise to lower the needle or
counterclockwise to raise the pointer.
Adjustment is very sensitive and
should require little force. Replac e the
meter cover and reinstall the meter into
the chassis.

Technical Assistance:

If you have any problem with this unit first check the appropriate section of
this manual. If the m anual does not reference your problem or your problem
is not solved by reading the manual you may call MFJ at 601-323-5869. You
will be best helped if you have your unit, manual and all information on your
station handy so you can answer any questions the technicians may ask.

You can also send questions by mail to MFJ Enterprises, INC., P.O . Box 494,
Mississippi State, MS 39762; by FAX to 601-323-6551; through Compuserve
at 76206,1763; or by email to [e-mail]. Send a
complete description of your problem, an explanation of exactly how you are
using your unit, and a complete description of your station.

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MFJ-862 SWR/Wattmeter

Schematic:

4