MFJ-926 Remote Automatic Antenna Tuner Instruction Manual
©
2006 MFJ Enterprises, Inc.
2
WARNING
●
Never operate the tuner with its cover removed. Contact with the components inside the
tuner while transmitting will result in painful RF burns.
●
Locate the tuner so that the top antenna terminals are not accessible during operation. The
antenna connection will have high voltage while transmitting.
●
Disconnect the tuner and radio from an antenna before lightning storms. DO NOT
ATTEMPT THIS DURING A STORM
●
Never exceed tuner specifications.
●
Do not transmit with a high SWR for extended periods of time. Check all connections if this
occurs.
Installations
The MFJ-926 can be installed for mobile or base station operation. For mobile operation the antenna
terminal should be connected to a suitable antenna. The ground should be connected to the body/frame of
the vehicle with a short heavy gauge wire or strap. Keep this connection to a minimum. Base station
installations may vary but all installations must have a suitable ground and a wire/antenna of suitable
length depending on the operating frequency.
Connections
1.
Connect the supplied power cable to a 13.8VDC source. The RED wire should be
connected to the positive (+) terminal of the source while the BLUE should be connected
to the negative (-) terminal. Check the polarity of the cable with a voltmeter before
connecting the auto-tuner. The 13.8VDC source must be capable of delivering a
minimum of 1 amp of current continuously. If the voltage is to low the tuner will not
power on.
2.
Connect your transceiver to the SO-239 connector on the antenna tuner using a good
quality 50 ohm coaxial cable. The coax should be kept to a minimum length.
3.
Connect a wire antenna / mobile whip to the antenna terminal on the top of the tuner.
The antenna must be a suitable length for proper tuning. Lower frequencies will require
longer antennas while higher frequencies require shorter lengths. If the antenna wire is to
short the tuner will not match the impedance of the antenna to the transmitter.
4.
Connect a suitable ground to the ground point on the bottom of the tuner. Read the
section below on ground systems.
Ground System and Counterpoise
The MFJ-926 must be connected to a good electrical ground. A good ground can prevent accidental
shocks, interference to other electronics and keep RF out of out of your shack. Use a heavy gauge wire or
metal strap to connect to a large as possible metal object. In addition to a good ground, a counterpoise
wire must be installed at a quarter wave length of the operating frequency.
Caution:
1.
To insure the proper tuning, the antenna must have enough length (See Antenna Length Section
below).
2.
Do not install a balun, it will cause a tuning problem. Calculation of undesirable antenna length:
Length of half wave = 300 / operating frequency (MHz) x ½.
