MFJ-259C Instruction Manual
HF/VHF SWR Analyzer
6
2.) Coax Loss: Use the analyzer's second mode to measure loss incurred in random lengths of 50-Ohm cable, 50-
Ohm attenuator pads, 50-Ohm transformers, and 50-Ohm baluns. The top working-display line shows the
VFO Frequency in MHz and the lower line presents the measured Loss in dB. Note that the transmission line
or device under test must be unterminated at its far end during loss testing. If a load or resistive
termination is installed, the measured loss will be significantly higher than the actual loss. Note that this
measurement mode only works for lines or devices carrying differential currents.
3.) Capacitance in pF: Use this mode for checking unknown capacitor values (in pF) and for determining how
much reactance a component exhibits at a particular frequency (Xc in ohms). In Capacitance Mode, the top
line of the working display shows the VFO Frequency in MHz and the measured Capacitive Reactance (Xc) at
the VFO frequency (in ohms). The lower line shows the measured capacitance (C) in picofarads (pF). The
analog Impedance meter also displays Xc reactance in ohms.
4.) Inductance in uH: In Inductance Mode, the top line of the working display shows the VFO Frequency in MHz
and the capacitive reactance (XL) at the VFO frequency (in ohms). The lower line shows the measured
inductance (L) in microhenries (
µ
H). The Impedance meter displays reactance in ohms.
5.) Frequency Counter: The fifth mode converts the analyzer into a discrete frequency counter. Connect the RF
source (DUT) to the BNC connector labeled Frequency Counter Input. As with many counters, the sensitivity
threshold for a locked-in reading gradually decreases with increasing frequency. The measurement threshold
at 0.53 MHz is around 10 millivolts -- and this level gradually increases to around 200 millivolts at 230 MHz.
The "never exceed" limit for safe testing is 2-volts peak-to-peak. The counter's default gate time is 0.1
second, but you may reset it to either .01 second (very fast) or 1.0 second (very slow) by tapping the Gate
button. A 1.0-second gate times provide increased frequency resolution (more digits to the right of the decimal
point), and the .01 gate provides very fast response with less resolution (see sample screens below):
IMPORTANT WARNING: Never apply more than two volts of peak voltage -- or any dc voltage -- to
the Frequency Counter BNC port.
3.4
Blinking “VOLTAGE LOW” display warning
If the external dc source or battery voltage drops below 11 volts, a blinking Voltage Low warning will come up on
the display. Pressing Mode during a low-voltage warning will disable it and allow you to continue testing.
Caution: Measurements made with supply voltages below 11 volts may not be as reliable.