RA.366 PANORAMIC ADAPTER |
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The maximum spectrum width that can be viewed is 1 MHz and this is selected by the MHz tuning control on the receiver.
When the Panoramic Adaptor is operated in the I.F. mode, spectrum analysis facilities are provided for signals in the I.F. passband
of the receiver and are selected by using the kHz tuning control.
In either mode of operation the displayed spectrum can be expanded to permit finite inspection of the selected signal.
Signals appear on the screen of the CRT as inverted "V" deflections; the signal to which the receiver is tuned being seen as a deflection near the centre of the screen. Other signals within the selected spectrum appear to the left or right of centre according to their frequencies, and as the receiver is tuned these deflections will move across the CRT. When a deflection approaches the centre of the screen, its corresponding signal will be heard through the receiver.
A tuning marker signal is derived from the receiver when the adaptor is used in the R.F. mode and marker pips appear on the screen at 100 kHz intervals when the receiver is set to CAL.
There are two type of adaptor RA.366 and these differ only in the power supply unit which is available for the panoramic adaptor. The units are identified as follows:
The 21 MHz signal is combined with 19.4 MHz from the crystal oscillator in the 2nd r.f. mixer. The 1.6 MHz i.f. output from the 2nd
r.f. mixer is passed through a low-pass filter to the i.f. module via the r.f. position of the r.f./i.f. selector switch.
The 1.6 MHz signal from the receiver is selected by the selector switch (r.f. position) on the front panel of the RA.366. In this mode,
the 1.6 MHz signal is amplified and taken via a bandpass filter to the 1st i.f. mixer of the adaptor.
In the "r.f." position of the selector, the mixer combines 1.145 MHz from the i.f. crystal oscillator with the 1.6 MHz signal to
produce 455 kHz.
In the "i.f." position, the r.f. section is switched out of the circuit and the 1st i.f. mixer then combines
the 1.6 MHz signal from the receiver with the sweep oscillator output (1.145 MHz ±40 kHz) to produce 455 kHz. The 455 kHz signal
is amplified and fed through the crystal filter.
The amplified 455 kHz signal is taken via the diode detector to a vertical amplifier
and the Y deflection plates of the CRT.
The horizontal sawtooth generator receives a synchronising pulse from the i.f. sawtooth generator and produces a time base deflection
voltage which is amplified by the horizontal deflection amplifier. The pulse is then fed to the horizontal deflection plates of the CRT.
The horizontal sawtooth generator also supplies a synchronising pulse to the r.f. sawtooth generator to ensure that all three sawtooth
generators are in synchronisation.
The r.f. sawtooth generator provides a sawtooth voltage to the r.f. sweep oscillator at a sweep rate of 4 Hz. This sweep rate is set
by an internal adjustment in the r.f. sawtooth generator. The oscillator sweeps from 23-24 MHz and is fed to the 1st r.f. mixer and
the 1st marker mixer.
An output of 3.6-4.6 MHz is taken from the 2nd V.F.O. of the receiver and is fed, via a low pass filter, to the 1st marker mixer of
the RA.366. A negative blanking pulse is also fed to the 1st marker mixer from a multivibrator which is triggered by the horizontal
sawtooth generator. The mixer combines the 3.6-4.6 MHz with the 23-24 MHz output from the sweep oscillator to produce 19.4 MHz.
The 19.4 MHz output from the 1st marker mixer is combined with 19.4 MHz from the r.f. crystal oscillator to produce a zero beat ±1 kHz
output. This signal is amplified and fed to a multivibrator which produces a wide positive going square wave. The wide pulse width is
necessary to prevent double pulsing of the marker generator by the audio signal on either side of zero beat.
The multivibrator square wave output is integrated to obtain a positive spike which is used to trigger a third multivibrator. This
multivibrator produces a positive square wave marker which is taken to the i.f. and detector module.
The marker pulse and the detected signal are taken simultaneously to the Y deflection plates of the CRT.
As the receiver is tuned (kHz),
the receiver's 2nd V.F.O. frequency (3.6-4.6 MHz) varies the position of the marker pulse relative to the 23-24 MHz horizontal time base.
A D.C./D.C. inverter produces the e.h.t. voltages to operate the CRT.