Electronic counter heterodyne method, block diagram
c. A harmonic generator produces all harmonics of 10 MHz.
selector cavity is manually tuned until the selected harmonic, mixed with the
input, produces a different frequency that is fed through an amplifier to the
A level meter indicates when the harmonic selector reaches the proper
To find the frequency being measured, add the reference
frequencies to the electronic counter display.
This addition usually involves
nothing more than placing one or two digits before the counter reading.
d. The transfer oscillator method (fig 3-11) provides an extremely wide
measuring range with counter accuracy.
used in conjunction with a 50-MHz electronic counter.
The transfer oscillator
(1) When you are measuring, adjust the fundamental frequency to the point
accomplished by beating harmonics against the input signal in a mixer and varying
the fundamental frequency until the difference frequency is zero. The results are
observed on a built-in scope.
(2) The counter can read out the unknown frequency which equals the
fundamental frequency multiplied by the harmonic number.
The proper harmonic
number, selected by the front panel harmonic preset switches, automatically expands
the counting period of the counter.
This expansion results in a direct
presentation of the input frequency in the readout of the counter.
(3) The transfer scope includes a phase lock that is designed to
synchronize itself with the input signal.
Changing the transfer oscillator
frequency to maintain a precise 1-MHz beat frequency compensates for any frequency
change in either the input signal or the transfer scope.
The automatic method (fig 3-12) makes it possible to obtain instantaneous