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INSTALLING YOUR TUNER: The MFJ-971 tuner may be stacked with a
companion MFJ transceiver and power pack, or used separately.
Two brackets and 8 screws are included in this package to connect
the tuner to the MFJ transceiver and power pack i f you choose to do
so. Locate your tuner to prevent accidental contact with connectors
on the rear panel; even low-power radios can cause serious RF burns
when fed into a random wire antenna. The tuner meter lamp may be
powered from any 12-VDC source. Use a 5.5mm x 2.1mm coaxial plug;
center pin positive (+).
TUNER CONNECTIONS: Set up your MFJ-971 as follows:
1. Connect radio to the SO-239 connector marked TRANSMITTER. 2.
Connect antenna feed to the appropriate tuner output:
(a.) COAX-FEED to the SO-239 connector marked ANTENNA.
(b.) RANDOM WIRE to the red binding post below ANTENNA jack.
(c.) BALANCED FEEDERS to the BALANCED binding posts.*
* WHEN USING BALANCED FEEDLINE, CONNECT A SHORT JUMPER FROM THE
LOWER "BALANCED" BINDING POST TO THE RED "ANTENNA" BINDING POST.
This routes the balun's unbalanced output to the tuner circuit.
3. Connect your tuner and transmitter to a good earth ground.
CAUTION: For reasons o f safety and radiation efficiency, random wire
antennas should be high, clear of obstructions, and at least 1/4
wavelength long. They should also be well insulated from humans,
animals, vegetation, and grounded objects.
OPERATING YOUR TUNER: If your radio has tube finals, set the
transmitter on-frequency and "tune up" into a 50-Ohm resistive load.
Once this i s done, leave your TUNE and LOAD controls set and
connect the tuner. If your radio has solid-state finals, omit this
step (it is already matched to
-
a 50-Ohm non-reactive load).
1. REDUCE TRANSMITTER OUTPUT before making initial adjustments.
2. Set tuner's TRANSMITTER and ANTENNA controls at 12:00 (3-1/2). 3
Switch INDUCTANCE for loudest receiver background noise.
4. Transmit a steady carrier ( a t low power), alternat
=
ely
adjusting TRANSMITTER and ANTENNA controls for minimum SWR.
NOTE: Since these controls interact, try moving the TRANSMITTER
control a small increment, then rotate the ANTENNA control for
minimum SWR. Repeat until you obtain the lowest SWR possible.
5. If you cannot obtain a 1:1 match, increase or decrease
INDUCTANCE and repeat step 4. Also, i f RF arcing occurs
inside the tuner, change INDUCTANCE and repeat step 4).
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