Solid State Shortwave Receivers For Beginners - The Listeners Guide

Using the Unit
Anyone familiar with calibration oscillators will probably be.
wondering what use a 200kHZ/1MHZ oscillator is when the S.W.
bands extend from about 1.6 to 30MHZ. Although it may appear
that this unit is of little use, this is not the case, as although the
fundamenta1 frequencies of oscillation are 200kHZ and 1MHZ, it also
provides outputs at harmonics of these frequencies. Harmonics are
simply the multiples of the fundamental frequency. Thus the 200kHZ
oscillator also produces signals at 400kHZ, 600kHZ, 800kHZ, and so
on. The 1MHZ oscillator produces signals at 2MHZ, 3MHZ, 4MHZ,
etc.
The 1MHZ oscillator will produce fairly strong calibration
signals to beyond 30MHZ, but the 200kHZ one will only provide
signals up to a few MHZ. This does not matter if one looks at it from
the practical viewpoint, as it is not really possible to calibrate the
tuning dial of a simple general coverage receiver at 200kHZ intervals
at high frequencies anyway. The calibration points would simply be
too close to one another. The upper limit of the useable 200kHZ
harmonics will depend upon the sensitivity of the receiver being
calibrated, and upon the individual components used in the oscillator.
An upper limit of something in the region of 10MHZ should be
obtained.
Before the unit can be used, it is necessary to adjust the outputs
to the correct frequencies. The easiest way of achieving this is to set
the unit up against B.B.C. Radio 2 on the long waveband, which
transmits on precisely 200kHZ. The unit should be set up in this way
prior to being used, each time it is used.
Initially the audio modulation should be off, and S1 should be -
in the ‘200kHZ’ position. Connect a lead to the output socket, and
place this near an operating receiver tuned to L.W. Radio 2. By adjusting
C4 it should be possible to produce the characteristic whistle of a
heterodyne between the fundamental signal of the calibration oscillator
and the carrier wave of Radio 2. Carefully adjust C4 to zero beat the
heterodyne. The calibration oscillator will then be working accurately
at 200kHZ.
It is a good idea to try adjusting the receiver’s tuning control
slightly. This should not affect the pitch of the hetenodyne. If it
should be found to do so, it means that the output from the calibration
oscillator is being received on a spurious response of the receiver.
It is then necessary to readjust C4 in an attempt to locate the
calibration signal on the receivers main response.
Next try to pick up the output of the oscillator on a S.W.
receiver. It should not be necessary to connect the output of the
calibrator directly to the receivers aerial terminal, and this could
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