Instruction manual

MFJ-207 Instruction Manual HF 10-160M SWR Analyzer
APPENDIX A
HOW TO ZERO BEAT THE MFJ-207 AGAINST THE RECEIVER
The Freq. Out jack on the MFJ-207 has a sine wave output which can be used to accurately check the frequency
at which the MFJ-207 is adjusted to.
To zero-beat against the receiver, loosely couple a wire from the RCA jack (Freq. Out) to the antenna connector
on your radio.
First, try a small length of wire from the Freq. Out connector of the MFJ-207. Just leave it dangling free, not
touching the Antenna input of the receiver. Place the far end of the wire near the receiver but do not connect it
to the receiver’s input unless you simply cannot hear the signal at all. The output of the MFJ-207 is a high level
and damage to the front end of some radios may occur with a direct connection, so you assume all risks in
making a direct connection.
Turn the radio on and tune to the frequency in question. For example, if you want to check your 40 meter
dipole on 7.235 MHz, set the radio for 7.235 MHz. Turn the RF gain and the Audio of you radio down as the
level of the MFJ-207 is strong. Put your radio in the CW mode. If you have a BFO adjustment on your radio,
be sure to set the BFO to ON and to 0 (zero).
Set the MFJ-207 to band C. Adjust the tune dial on the MFJ-207 until you start hearing a tone in the radio’s
speaker. As you slowly turn the TUNE dial, the frequency will start at a very high pitch, and then decrease to
zero pitch. The point where the tone goes to zero hertz is the “zero-beat”. That means the MFJ-207 is set
exactly to the setting on the radio.
Now make a note of where the dial is set on the MFJ-207 so you can re-set the frequency if you accidentally
bump the TUNE control.
You can now disconnect the wire and re-connect the antenna to the MFJ-207.