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MFJ-1623 Instruction Manual
Using the MFJ-1623
CAUTION:
Never Change The Antenna or Inductor Selector Switch Position While
Transmitting! Never Apply More Than 200 Watts To The MFJ-1623.
Preset the controls on the MFJ-1623 as follows:
• ANTENNA to maximum inductance - Position "A".
• MATCHING to minimum capacitance – Position "10"
• NORM/+C switch to NORM
• COUNTERPOISE to minimum inductance – Position "L"
• Hi-Z/Lo-Z switch (back of unit) to Lo-Z.
• SENSITIVITY control fully clockwise (maximum sensitivity)
Most modern solid state transceivers do not require tuning and loading adjustments. If the transceiver
has a built in antenna tuner, be sure it is turned off or disabled. If your transmitter has an adjustable
output circuit, it must be properly tuned to a 50 ohm load at the operating frequency before adjusting
the tuner. This should be done with a dummy load.
Tuning Procedure
WARNING: Never transmit while changing the INDUCTOR SELECTOR.
1) First, tune for maximum receiver noise as follows:
• While listening to your desired receive frequency, adjust the ANTENNA control for
maximum receiver noise.
• Adjust the MATCHING control for maximum receiver noise.
• Adjust the COUNTERPOISE control for maximum receiver noise.
Note: If no noise peak is evident, try adding extra capacitance with the NORM/+C
switch. Then reverse the HI-Z/LO-Z switch and re-try with both positions of the
NORM/+C switch.
2) Apply just enough power on CW (or AM/FM/RTTY) to obtain a noticeable deflection on the RF
CURRENT meter.
3) Carefully adjust the ANTENNA, MATCHING and COUNTERPOISE controls for maximum RF
current as follows.
• Adjust the MATCHING capacitor for maximum RF current.
• Adjust the COUNTERPOISE inductor for maximum RF current.
• Try plus or minus a position or two on the ANTENNA inductor, along with tuning the
MATCHING capacitor to see if higher RF current is achievable.
Window/Balcony Mount Antenna
3
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