MFJ-259 Instruction Manual
HF/VHF SWR Analyzer
4
Feedlines with very low losses, such as air insulated transmission lines, will not have much
loss even when operating at extremely high SWRs. High loss cables, such as small
polyethylene dielectric cables like RG-58, will rapidly lose efficiency as the SWR is
increased. With high loss or long feedlines it is very important to maintain a low SWR over
the entire length of the feedline.
Any SWR adjustments have to be made at the antenna, since any adjustments at the
transmitter end of the feedline can not affect the losses, nor the efficiency of the antenna
system.
Measuring SWR
The MFJ-259 will measure the impedance ratio (SWR) of any load referenced to 50 ohms.
The SWR can be measured on any frequency from 1.8 to 170 MHz. No other devices are
required.
The "ANTENNA" connector (SO-239 type) on the top of the MFJ-259 provides the SWR
bridge output connection. To measure SWR, this connector must be connected to the load or
device under test.
WARNING:
Never apply power to the "ANTENNA" connector.
To measure the SWR of a 50 ohm coaxial line simply connect the line to the "ANTENNA"
connector. The counter input should be set to "A". Press the "Input" button until the "A"
appears on counter display.
To measure the SWR on a predetermined frequency adjust the "TUNE" and "FREQUENCY"
knobs until the counter displays the desired frequency. Read the SWR from the "SWR"
meter.
To find the lowest SWR adjust the frequency until the SWR meter reaches the lowest reading.
Read the frequency of the lowest SWR directly from the counter display.
Note:
The internal oscillator of the MFJ-259 will not produce an entirely stable reading on
the frequency display due to short term drift in the oscillator. This drift is normal and
does not affect the accuracy, results or usefulness of this instrument since a null will
even be maintained on the highest Q (narrow bandwidth) antennas or loads.
It is perfectly acceptable to ignore decimal place readings more than two places to the right of
the decimal point in the counter (ten's of kilohertz) above 15 MHz and three places to the right
of the decimal point (kilohertz) below 15 MHz.