signal in a mixer and varying the fundamental frequency until the difference
frequency is zero. The results can be observed on a built-in oscilloscope.
The counter is able to read out the unknown frequency, when the fundamental
frequency is multiplied by the harmonic number, by use of the front panel
harmonic preset switches.
The proper harmonic number will automatically
expand the counting period of the counter.
This expansion results in a
direct presentation of the input frequency in the readout of the counter.
The transfer oscillator includes a phase lock that is designed to
synchronize itself with the input signal. Any tendency in frequency change
in either the input signal or the transfer oscillator can be compensated.
This compensation is accomplished by changing the transfer oscillator
frequency in order to maintain a precise 1 MHz beat frequency with the input
signal.
Figure 11.
Transfer oscillator method.
11
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