MFJ-266C HF/VHF/UHF Antenna Analyzer
Instruction Manual
Version 2A
13
2012 MFJ Enterprises, Inc
serve as a pickup device. The usable signal range is around 30-dB (30-mV to
1-V rms). Note that the display reading is a RMS level taken directly from
the MCU detector, so it must be multiplied by 1.414 to obtain a peak AC
value (
V-rms x 1.414 = V-p
, conversely
V-p x .707 = V-rms
). Also, despite
the display's 0.1 mV resolution,
readings will be approximations
rather than
precise values because of detector non-linearity.
The
Danger - High FS
display warning means a dangerously strong signal is
being applied and the level should be reduced immediately. Also,
interference greater than 100 mV will almost certainly cause inaccurate
SWR measurements when in Analyzer mode.
7.3 Stimulus Generator as a Signal Source
When operated in Analyzer mode, the MFJ-266C generates a +2 dBm CW
carrier (2 mW). See section 3.6 for setup procedures. Output will vary
slightly, depending on frequency and operating voltage, but typically holds
to within 1-2 dB of the rated power level over the analyzer's frequency
range. Second-harmonic suppression averages -20 dBc. A quarter-wave stub
or low-pass filter may be installed if greater harmonic suppression is
required for a specific application. Frequency stability and carrier purity are
sufficient for testing filters, mixers, low-power amplifier stages, and for
checking antenna patterns when a range antenna is connected to the analyzer
output. The stimulus generator may also be used for producing lower-level
signals with a suitable precision RF attenuator installed in line. When
connecting the generator directly to active circuitry, always insert a coupling
capacitor to prevent DC voltages from back-feeding into the bridge circuit
and destroying the detector diodes. Also, avoid connecting the stimulus
signal directly to sensitive preamps or receiver circuits that could be
damaged by an un-attenuated 2-mW signal.
7.4 Measuring Unknown Capacitance
To measure capacitance, connect the unknown component to the
Antenna
connector (usable range is from approximately 15 pF to 1200 pF). To enter
the
Capacitance
mode, begin with the analyzer turned off, then
press and
hold
the
Up
button while pressing the
PWR
switch (see Section 3.6). The
screen will display the approximate value of the unknown capacitor in pF
along with the stimulus frequency where the measurement is being made.
Note that you will not have full control over stimulus-frequency
Band
selection in this mode. Of the bands offered, the best accuracy is typically
obtained on
Band C
,
w
hich may be selected using the
Up/Down
switches.
Note that any capacitor and lead combination that approaches self-resonance
at the stimulus frequency will trigger the C
= Xc >1.5K
Ω
message and will
be un-measurable. Attempt to re-measure at a lower frequency.
