The spurs come from the second harmonic of the LO and a little from the
second harmonic of the IF. The IF is right about 9 MHz and fixed, so
that spur stays on 18.0 MHz. The LO injection is 9 MHz + the offset from
18 MHz, so if the dial shows 18.100, the spur is on 18.200, outside the
band. The LO spur is the strongest of the two.
Those two are the major spurs. There may be more depending on the
intermod of the mixer and stages following the mixer handling all those
signals.
73, Jerry, K0CQ
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Entire content copyright Dr. Gerald N. Johnson, electrical engineer.
Reproduction by permission only.
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