Operating instructions

MFJ-933 Loop Tuner

Instruction & Technical Manual

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FAST-START INSTRUCTIONS

Step 3

Pre-set the MFJ – 933 Loop Tuner controls to the following settings for the 14.2

MHz operation (settings are approximate, but should be reasonable):

• TUNING control to position “4 ½ ”.

• MATCHING control to position “9”.

Step 4

Tune the transceiver or receiver to the 20 meter band and frequency of interest

and “Ear-ball” fine-tune the MFJ-933 Loop Tuner

controls for maximum noise

and S-Meter reading. “Ear-balling,” like “Ball-parking” is a term often to describe

the listening process as used to hear a “peak” in reception before actually

applying a transmit signal to the tuner. The tuner will produce a peak when the

exact position for the controls and switches is found.

Step 5

Apply 10 to 20 Watts of power to the MFJ – 933 Loop Tuner and adjust the

TUNING and MATCHING controls for minimum SWR. Readjust the controls until

you see no further improvement in minimum SWR.

Step 6

Once you are satisfied that the adjustments and settings are correct for minimum

SWR and maximum antenna current, you can advance the power to 150 Watts if

desired. Be sure that MPE distance standard is met. Should any arcing be

detected, stop transmitting and check connections and proximity to objects that

may be suspect. If arcing seems to be inside of the MFJ – 933, Loop Tuner,

lower output power and re-check for arcing.

As a courtesy to our fellow hams, for safety and to keep within FCC regulations

you should use the minimum power needed for communications. 20 to 50 watts

often provides very reliable communications. The difference between 50 and

100 watts is less than ½ S-unit and is not noticeable on the receiving end.