MFJ-269C Instruction Manual LF/HF/VHF/UHF SWR Analyzer
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1. Terminate the line or antenna in a non-inductive resistance somewhere around the expected value.
2. Connect the transmission line or antenna directly to the MFJ-269C Antenna connector. Adjust the
frequency (near the expected operating frequency) until the lowest resistance and lowest reactance is
measured.
3. Record the impedance value.
4. Adjust the frequency until the highest resistance and lowest reactance is measured.
5. Multiply the highest resistance by the lowest resistance, and find the square root of the result.
Example: The highest resistance is 600 ohms, the lowest is 400 ohms. 400 x 600 = 240,000. The
square root of 240,000 is 490. The impedance is 490 ohms.
Using a potentiometer or resistor decade box:
1. Connect the MFJ-269C to one end of the system (in this case you can use a broadband matching
transformer).
2. Adjust the frequency and note only the SWR change.
3. Adjust the termination resistance until the SWR remains as constant as possible with very large
frequency changes around the operating frequency range.
4. The resistance of the termination resistor is the surge impedance of the system.
The electrical length of the Beverage can be determined by using procedures outlined in Advanced 2.
7.4 Adjusting Tuners
The MFJ-269C can be used to adjust tuners. Connect the MFJ-269C Antenna port connector to the
tuner's 50-ohm input. Connect (or select) the desired antenna to the tuner output. This connection may be
made with a manual RF switch to facilitate rapid changeover, provided that switch has better than 50-dB
port isolation.
WARNING: ALWAYS CONNECT THE COMMON (ROTARY CONTACT) OF THE SWITCH TO THE
TUNER. THE SWITCH MUST CONNECT EITHER THE MFJ-269C OR THE STATION
EQUIPMENT TO THE TUNER. TRANSMITTING EQUIPMENT MUST NEVER BE
CONNECTED TO THE MFJ-269C.
1. Connect the MFJ-269C to the tuner input.
2. Turn on the MFJ-269C and adjust it to the desired frequency.
3. Adjust the tuner until the SWR becomes unity (1:1).
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