MFJ MFJ-269 - Page 37

MFJ-269 Instruction Manual HF/VHF/UHF SWR Analyzer
37
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-269 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-269 can be used to adjust tuners. Connect the MFJ-269 "ANTENNA" connector to the tuner's 50 ohm
input and the desired antenna to the normal tuner output. This connection can 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-269 or the station equipment to the tuner.
Transmitting Equipment Must Never
Be Connected To The MFJ-269.
1.
Connect the MFJ-269 to the tuner input.
2.
Turn on the MFJ-269 and adjust it to the desired frequency.
3.
Adjust the tuner until the SWR becomes unity (1:1).
4.
Turn off the MFJ-269 and re-connect the transmitter.
7.5 Adjusting Amplifier Matching Networks
The MFJ-269 can be used to test and adjust RF amplifiers or other matching networks without applying operating
voltages.
The tubes and other components should be left in position and connected so that stray capacitance is unchanged.