MFJ-259B Instruction Manual HF/VHF SWR Analyzer
3
Component limitations are another source of inaccuracy.
Diodes detecting very small voltages are non-
linear. The accuracy of the MFJ-259B is enhanced by the use of special microwave zero-bias Schottky detectors
with matching compensating diodes. Each unit is individually compensated to provide the best possible linearity
with both high and low impedance loads, making the A/D converter's 1/2 percent resolution the primary
limitation.
Connection lengths are another problem.
Connection lengths between components in the bridge and the
bridge and output connector upset readings, especially when the impedance is very high or very low. The MFJ-
259B minimizes this problem by using surface mount low capacitance microwave components with nearly zero
lead length.
Unlike instruments that present readings outside the reliable range as exact numbers, the MFJ-259B gives a
display warning. If (Z>650) appears on the display, the impedance is greater than 650 ohms and outside the
reliable instrument range.
1.2 Typical Uses
The MFJ-259B can be used to adjust, test, or measure the following
:
Antennas: ...................................SWR, impedance, reactance, resistance, resonant frequency, and bandwidth
Antenna tuners:..........................SWR, bandwidth, frequency
Amplifiers:.................................Input and output matching networks, chokes, suppressors, traps, and components
Coaxial transmission lines:........SWR, length, velocity factor, approximate Q and loss, resonant frequency, and
impedance
Filters:........................................ SWR, attenuation, and frequency range
Matching or tuning stubs: ..........SWR, approximate Q, resonant frequency, bandwidth, impedance
Traps: .........................................Resonant frequency and approximate Q
Tuned Circuits: ..........................Resonant frequency and approximate Q
Small capacitors:........................Value and self-resonant frequency
RF chokes and inductors: ..........Self resonant frequency, series resonance, and value
Transmitters and oscillators:......Frequency
The MFJ-259B measures and displays the following:
Cable length (feet)
Impedance phase (degrees)
Resonance (MHz)
Cable Loss (dB)
Inductance (uH)
Return loss (dB)
Capacitance (pF)
Reactance or X (ohms)
Signal Frequency (MHz)
Impedance or Z magnitude (ohms)
Resistance or R (ohms)
SWR (referenced to 50 ohms)
The MFJ-259B is useful as a non-precision signal source.
It provides a relatively pure (harmonics better
than -25 dBf) signal of approximately 3 Vpp (approximately 20 milliwatts) into 50 ohm loads. The MFJ-259B
internal source impedance is 50 ohms.
Note
:
A more complete description of the MFJ-259B's features and proper measurement methods
can be found by reading the sections on the particular measurement you wish to make.
Consult the table of contents for the various applications.
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