MFJ-1784
Giant Box Fan Portable Loop Antenna
Instruction & Technical Manual
3.1
CONTROLS & CONNECTIONS
The controller box (Figure 6) can be installed at any position that allows easy access to it and the
transceiver. The coax line between the controller and antenna should be good quality 50Ω cable
and be kept as short as practical to reduce losses. If you use quality low-loss cable the exact
lengths used are not important and will not effect the operation or SWR of the system. If you are
using a lossy cable between your antenna and controller and have problem tuning, the easiest way
to correct the problem is to get better quality cable. The MFJ-1783 controller box requires an 18
VDC 500 mA, ungrounded power supply. The power jack accepts a 2.1 mm coaxial plug with the
center conductor positive. The provided DC power supply will supply the correct power to the
controller box. There is also an internal battery bay with space for two 9V batteries. If you chose
to use a different power supply than the one provided, the power supply must not share a common
ground with anything else in your radio system.
Figure 6: Super Hi-Q Loop Remote Control
The controller supplies the control signals to the loop antenna through the coaxial feedline. These
signals are low voltage and low current so that the length of the coaxial line does not affect the
operation of the motor. It is important that the feedline remain water-free and that there are no
short circuits between the center conductor and the shield of the feedline.
The controller box has seven buttons and two LEDs on the front panel. The first three from the
left are Power, Meter Range, and lamp toggle. The remaining four buttons are assigned to UP and
DOWN labels that correspond to the frequency of the SWR minimum. The button groups are as
follows: FAST TUNE and FINE TUNE. The FAST TUNE group is used to quickly reach the
approximate tuned position. The FINE TUNE group slowly pulses the motor to allow for minute
adjustments. The SWR notch is very narrow, especially at lower frequencies. The control unit has
the added funtionality of an automatic fast search. When either the UP or DOWN fast buttons
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Summary of Contents for MFJ-1784
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