General Operation And Troubleshooting - MFJ Box Fan -1780 Instruction Manual

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MFJ-1780 Box Fan    Loop Antenna

5 - Cycle the loop to the top of it's tuning range by pressing the Fast Tune "UP" button. The FREQ

"UP" LED should light until the loop reaches the highest frequency and extinguish (approx. 20-

45 seconds). release the "UP" button.

6 - Repeat the two previous steps using the Fine Tune "DOWN" and "UP" buttons. The "DOWN" or

"UP" LED should flash off and on while the loop is tuning then extinguish when the upper or

lower tuning range is reached.

IF ALL OF THE TESTS WORK YOU ARE READY TO APPLY RF TO YOUR NEW ANTENNA.

CONTINUE WITH THE FOLLOWING:

7 - Adjust your transmitter to any desired frequency between 14.0 and 30 MHz and apply a small

amount of unmodulated carrier to the loop between 1 and 15 watts.

8 - Press the Fast Tune "DOWN" Button while carefully monitoring the reflected power if a power

meter is being used, or the SWR if an SWR meter is being used. The frequency "DOWN" LED

should light and the capacitor should turn. While carefully monitoring the meter used, watch for a

sharp dip on the meter. When a dip is located, release the Fast Tune "DOWN" button quickly.

9 - If you pass the dip simply use the Fine Tune buttons in the reverse direction to bring the capacitor

back to the tuning position with the lowest SWR.

Note: The tuning of this antenna is very sharp due its high Q and narrow bandwidth

Now you have successfully tested and operated your MFJ Box Fan Loop installation. You should now

be familiar enough with the controller box and its controls buttons.

Please remember the followings while tuning your antenna

MAKE SURE THERE IS NO ONE close to or touching the antenna. Make sure the antenna is

away from power lines and metallic objects. Use only low power during the tuning process.

THE TUNING OF THIS ANTENNA IS VERY SHARP due to the extremely high "Q" of the loop.

The same thing that makes the loop work so well is what makes the tuning so sharp. If you move more

than a few KHz in frequency you will probably want to adjust the SWR. After you use the antenna

experience will help you decide when to use the Fast Tune or Fine Tune buttons.

TO PROPERLY TUNE THE LOOP ANTENNA on Fast Tune, the controller box must have between

100 mW and one hundred watts of RF power at the desired operating frequency applied to it, with one

to 15 watts being the best power range. Although very little power can be radiated until the loop is

tuned, please use the least power necessary during tuning.

avoid causing interference.