Marconi 1475 R1475 Type RG 44 Receiver AP2883G

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Receiver 1475 Type R1475 RG.44. Marconi High-Discrimination Communication RG44 AP2883G

This receiver with its associated power supply unit was a piece of equipment of exceptionally high performance in sensitivity, selectivity and frequency stability.

It incorporated the then most recent advances in electrical and mechanical design techniques, it was suitable for operation from either AC mains or battery.

The receiver used a super-heterodyne circuit with twelve valves and a visual tuning indicator which , in conjunction with the new type of greatly extended tuning scale, permitted accurate tuning to within an audible beat note of any given frequency in the band of 2 to 20 Mc/s.

In appearance this equipment departed from the conventional lines, since the special tuning unit  and scale occupied a considerable portion of the front panel.

Tuning adjustments were effected by means of two large knurled thumb controls, placed for convenience in operating at one end of the tuning drum, at the other end is the wave-change lever, all other controls were arranged in two rows below this.

High-discrimination, direct-reading tuning scale
This took the form of a drum on which the entire tuning scale is printed in spiral form so that the developed length of the scale was nearly 30 feet.
It was graduated at 10kc/s intervals throughout the entire band, the scale separation between marks being 3/16" up to 11.3 Mc/s and more than 1/8" up to 20 Mc/s.

As the drum was rotated by means of the knurled thumb wheel, moving pointers indicate on which spiral the frequency required was to be read. A static horizontal scale associated with the pointers indicated the frequency in whole numbers of Mc/s. Frequency-calibration check points were clearly marked at 600 kc/s intervals on the drum.

Frequency Calibration-scale checking
Facilities were provided in the receiver for checking the accuracy of the scale calibration to very fine limits and for correcting the calibration when necessary.
The harmonics of the crystal controlled 2nd heterodyne oscillator were fed back to the anode circuit of the RF amplifier valve, which was itself switched off so that all other carriers which might cause confusion are excluded from the mixer and subsequent stages.

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By this means whistles were produced at 600 kc/s intervals throughout the tuning range and the positions at which they should be heard were marked on the rotating scale.
If however the carrier whistles do not correspond to the scale check points, they can be made to do so by means of the "Scale Trimmer" control. This control was in effect an inductance trimmer, by means of which a constant percentage control of the1st heterodyne oscillator was obtained. In this way changes due to drift can be corrected through -out the whole of the bands and constant re-checking was therefore un-necessary.

In addition to the precision tuning-adjustment facility a further innovation was introduced in this receiver in the form of a device which enables reception on a fixed frequency between 2 to 7.5 Mc/s,(150 to 40m), (e.g. Guard Frequenc
y) to be carried on simultaneously with the reception of signals on any other frequency (or on the same frequency).

Thus on one receiver a double watch could be kept. This dual channel effect was obtained by the use of a second mixer valve which performed the combined functions of an auxiliary mixer and auxiliary oscillator.
The oscillator was controlled by a standard plug-in crystal, and the HF circuit associated with this channel takes the form of a unit which is plugged into the front of the set.

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When the guard- frequency valve was switched on, a signal on that frequency breaks through, irrespective of the frequency to which the main tuning controls were set.

Frequency Coverage
2 to 20 Mc/s (150 to 15m) in 4 Bands.
Band1 :- 2 to 3.6 Mc/s.
Band 2 :- 3.6 to 6.4 Mc/s.
Band 3 :- 6.4 to 11.3 Mc/s.
Band 4 :- 11.3 to 20 Mc/s.

To suit 60, 150, or 2000 ohm resistance telephones adjustable by tapped output transformer.
600 ohm balanced and un-balanced outputs, high or low level.

Three switch-selected bandwidths available; 5 kc/s,1200 c/s and 300 c/s, including LF filters.

Power Supply Unit
200/250volts AC (50 c/s).

60 watts or 4 amps from 12 volt accumulator. Appropriate tapping's available on transformer.

HT 260 volts DC, 65mA. LT 12.6 volts AC, 2.0 Amps.

The receivers weight
40 lbs -18 3 kg. The supply unit weighs 25 lbs - 11.3kg.

We supply two Manuals for the The Receiver R1475 1475 RG44.
Manual AP2883G containing 59 A4 pages including Circuits, Component lists and Alignment.
Manual T1980
which contains 74 A4 pages including Circuits, Component lists, Alignment and seven pages of modification notes.

Total of 133 Pages.
Manuals are Available Worldwide as a Download.

Manual 133 A4 pages worldwide

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We do all we can to provide the very best that is available for you.
But in the unlikely event that any data should not be as you expected.
A refund is always available. Kind Regards Allen and Alanna.

Manuals are Available Worldwide as a Download

Thank you for your interest. Allen and Alanna G0RIT
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Revised: February 09, 2021