MFJ-269 Instruction Manual HF/VHF/UHF SWR Analyzer
11
The out-of-range frequency warning displays are:
IN C R EA SE
D EC R EA SE
FR EQ U EN C Y
Be sure the
“FREQUENCY MHz”
selector is in the correct extreme counterclockwise position for UHF
operation. Adjust the
“TUNE”
control for the correct frequency range.
4.0 Main (or Opening) mode
Main
CAUTION: THERE IS A ‘‘UHF’’ SWITCH LOCATED AT THE UPPER LEFT-HAND
SIDE OF THE ANALYZER. THIS SWITCH SHOULD BE PRESSED AND
LOCKED FOR UHF OPERATION ONLY WHEN UHF OPERATION IS DESIRED
AND ONLY AFTER THE UNIT IS POWERED UP. FOR INFORMATION ON
UHF OPERATION, SEE SECTION 3.4
WARNING: Never apply RF or any other external voltages to the ANTENNA port of this
unit. This unit uses zero bias detector diodes that are easily damaged by external
voltages over a few volts. Be sure the power supply is correct, as described in section
2.0, before operating this unit.
A basic understanding of transmission line and antenna behavior and terminology is very important in
understanding information provided by the MFJ-269. Most explanations are available in the ARRL Handbooks,
and they should suffice for amateur applications. Avoid relying on popular rumor, or unedited, poorly edited, or
self-edited handbooks or articles.
4.1 General Connection Guidelines
a.) The
ANTENNA
connector (Type “N” female) on top of the MFJ-269 provides the RF measurement output
connection. This port is used to measure SWR or perform other RF impedance measurements, with the exception
of the Frequency Counter mode.
Warning:
Never apply external voltages or RF signals to the antenna connector.
b.) Remember to use proper RF connections. Keep leads as short as possible when measuring components or any
system or device that is not part of the entire system. When measuring 50 ohm coaxial systems or antennas,
interconnecting transmission lines may modify impedance and SWR. Use properly constructed 50 ohm coaxial
cables of known quality.
c.) Advanced 3 modes allow user selection of custom impedances in case the system under test is not a 50 ohm
system.