Using the MFJ-945E:

The INDUCTOR switch on the MFJ-945E represents maximum inductance at position A and a
minimum inductance at position L. Less inductance is needed at higher frequencies than at low
frequencies for the same impedance. The TRANSMITTER and ANTENNA controls both
represent maximum capacitance at position 10. For optimum operation of the MFJ-945E, the
transmitter must be tuned to a 50 Ohm output impedance at the operating frequency.  
Always tune the transmitter at a low output power! 
Do not readjust the transmitter loading control setting after loading it to a 50 Ohm load! After properly tuning the transmitter, tune the MFJ-945E for a minimum SWR as described below:

When using the MFJ-945E for receiving only, tune as described in Steps 1 and 2.

1. Set the TRANSMITTER and ANTENNA controls to position 5. The tuning capacitors are half opened at this setting.

2. Rotate the INDUCTOR control until maximum noise is obtained with your tranceiver in the receiving mode.

WARNING: Never transmit while changing the INDUCTOR setting!
3. While transmitting a steady state carrier (CW), alternately adjust the ANTENNA and TRANSMITTER controls for minimum SWR. Since both of these controls interact, the two controls can best be adjusted by turning the TRANSMITTER control a small increment at a time, then rotating the ANTENNA control for minimum SWR. Repeat this procedure until minimum SWR is obtained.

4. If an SWR of 1:1 is not obtained, increase or decrease the INDUCTOR control and repeat Step 3. If arcing should occur between the capacitor plates, increase or decrease the INDUCTOR control one position, then repeat Step 3. NOTE: If you can’t obtain a 1:1 SWR, repeat Step 3 for each INDUCTOR control position.
5. After minimum SWR is achieved, transmitter power may be increased up to 300 Watts. Your MFJ-945E will reduce the SWR of most feed systems to 1:1. In some cases, a 1:1 SWR is not possible. Increase or decrease the length of your antenna to improve SWR.

6. An SWR of 1:1 may occur at more than one set of control settings on your MFJ-945E. When an SWR of 1:1 is obtained, check transmitter power. Ensure that transmitter power is relatively high. If transmitter power has decreased substantially, try another INDUCTOR control setting and repeat Step 3.


An amateur radio operator, Royal Signals veteran, jack of all trades and master of none.

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