MFJ-204B ANTENNA BRIDGE
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Thank you for purchasing the MFJ-204B Antenna Bridge. The MFJ-204B provides
an inexpensive and simple way to tune your antenna to match the feed-line and
transceiver from 160M thru 10M. The MFJ-204B also can be used to adjust the
matching device to the impedance of the feedline and enable you to obtain
proper load to your transmitter at any frequency using an antenna tuner
without having to key your transmitter while tuning
A 9V battery or a 12V DC adapter (MFJ-1312) can be used to power the MFJ204B.
To install the battery, remove all screws on both sides of the box and open
the case. Place the battery in the holder and connect the battery snap.
The RESISTANCE control is marked with letters from A thru G. These letters
correspond to the resistance value on the calibration chart on the bottom of
the MFJ-204B. Each mark is individually calibrated for better accuracy. A
frequency counter can be connected to the Frequency Output of the MFJ-204B to
get an accurate reading.
USING THE MFJ-204B ANTENNA BRIDGE
I. Measure antenna impedance at the antenna feed point.
1. Turn on the MFJ-204B.
2. Set the Band switch on the MFJ-204B to the desired band.
3. Turn your receiver to the desired frequency.
4. Connect a short piece of RG-58U or RG-8U with PL-259 (use your
wattmeter patch cable if desired) to the Coax Antenna connector
of the MFJ-204B.
5. Hold one end of the coax patch cable close to the antenna input of
your transceiver. Do not make physical connection.
6. Tune the TUNE control on the MFJ-204B until the oscillator can
be heard on the receiver. Make note of this TUNE control setting on
the
MFJ-204B. DO
NOT re-adjust.
7. Disconnect the patch cable.
8. Relocate the MFJ-204B close to the antenna feed point. Connect the
MFJ-204B to the antenna feed point with a RG-8U or RG-58U. Make
this cable as short as possible.
9. Turn the RESISTANCE control until a maximum dip on the meter can be
achieved. Note that a complete dip to "0" on the meter may not be
possible. In any case try to obtain the minimum meter reading.
10. Read the antenna resistance on the RESISTANCE control.
II. Adjust the antenna for resonance frequency.
1. Follow step from 1 thru 9 on section I.
2. If the resistance does not read 50 ohm, set the RESISTANCE control
to 50 ohm.
3. Adjust your antenna until the meter of the MFJ-204B reads minimum. At
this point the feed point impedance of the antenna is 50 ohm at the
frequency which was selected.
III. Using the MFJ-204B to tune an antenna tuner.
1. Turn on the MFJ-204B.
2. Set the Band switch on the MFJ-204B to the desired band. 3.
Turn your receiver to the desired frequency.
Summary of Contents for mfj-204b
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