MFJ-1644 Deluxe Whip Tuner
Instruction Manual
4
Antenna Hints
WARNING:
For operator safety, a good earth ground should be installed and connected to
the case of the MFJ-1644. Make certain the safety ground connects to the
same terminal that connects to the transmitter and other station accessories.
A binding post labeled "COUNTERPOISE" is provided for counterpoise or
other RF ground connection(s). This post
will not
provide a safety ground.
Matching Problems
Most matching problems occur when the antenna system presents extremely high impedance to the
tuner. This occurs when the antenna is approximately a half-wavelength long at the frequency at which
you are trying to tune.
MFJ-1644 Artificial Ground
The MFJ-1644 contains a series L-circuit that is used to tune the RF ground system (either a
counterpoise or a ground wire). Maximum ground current will flow through the MFJ-1644 RF current
meter when the COUNTERPOISE switch is properly set.
Installation of a Suitable Counterpoise / Artificial Ground
The MFJ-1644 includes a counterpoise set of wires that will work well from 80-10 meters. It is
important to keep the last few feet of the counterpoise wires as far as possible (two feet minimum) from
each other and other near-by conductors.
You can also build your own counterpoise system if you desire. A RF counterpoise system can be as
simple as a single wire a quarter wave long or less, or as complicated as several wires cut for different
bands. Always insulate counterpoise wires and keep them from accidentally contacting animals, people,
RF sensitive devices and wiring. For best performance, try to position the counterpoise wires in a
straight line if possible.
A counterpoise wire
must be well insulated
. For best performance, several wires a quarter-
wavelength long on different frequencies should be connected together at the COUNTERPOISE post
of the MFJ-1644.
When counterpoise wires are located indoors, they can be laid on a floor under a carpet, placed in an
attic, or stapled to a basement ceiling. If you place the counterpoise under the carpet or where
someone may contact it, be sure to use well insulated wire and multiple counterpoise wires. Insulate the
far end of the counterpoise wire(s) with electrical tape to prevent accidental contact.
