RA.63 SINGLE  SIDEBAND  ADAPTOR

HIGHLIGHTS

Pilot carrier and suppressed carrier reception

Upper or lower sideband selection

50 dB unwanted sideband rejection

Entirely self-contained

The stronger built RA.63H version

The Single Sideband Adaptor type RA.63 enables users to take full advantage of the very high stability of the RACAL RA.17 H.F. Communications Receiver to receive s.s.b. radio telephony. The adaptor is extremely versatile, being capable of receiving all conventional s.s.b. transmissions and d.s.b. radio telephony. Singe sideband reception of d.s.b. signals offers great advantages in that the effects of selective fading are reduced and adjacent channel interference can be minimized by choosing the better sideband.

Switched filters are employed, enabling alternative upper or lower sideband operation. These filters are designed to provide a bandwidth of 2500 Hz with a sharp cut-off to ensure satisfactory suppression of the unwanted sideband and of the residual carrier.

The unit is wholly self-contained, incorporating its own power supply and a.f. circuits. The only connection to the receiver is that to the 100 kc/s i.f. output socket, leaving normal operation of the receiver unchanged provided that a high stability receiver, such as the RACAL RA.17 or RA.117 is used.

Two standard versions of the adaptor are available, the RA.63G for the British market and the RA.63H, which is designed to North American standards. These differ only in mechanical details of plugs and sockets.
A third version is available for use where improved frequency stability is required, designated RA.63D. This version incorporates a crystal controlled 82 kHz oscillator in place of the L/C oscillator.
There is also a RA.63K, but the RA.63D and RA.63K are described in a separate handbook, which I do not have ...

Other variants of the RA.63

RA.63A   For use with receivers having 100 kc/s i.f. outputs. RA.63B   As RA63.A but American type plugs and sockets are used. RA.63C   For use with receivers having 465 kc/s i.f. outputs. RA.63E   For use with receivers having 455 kc/s i.f. outputs. RA.63G   As RA63.A but made stronger by addition of side panels. RA.63H   As RA63.B but made stronger by addition of side panels. RA.63L   As RA63.E but made stronger by addition of side panels.

RA63.A without the side panels

The input to the RA.63 is mixed with the output from a stable L/C oscillator operating at a nominal frequency of 82 kHz. The frequency of this oscillator is variable over a range of +/- 1 kHz and provides the accurate control of tuning essential to take full advantage of the carrier and unwanted sideband rejection given by the sideband filters.

In the RA.63D an ovened crystal is incorporated for extra stability.

The mixer output, centred at 18 kHz, is passed to either the upper or lower sideband filter according to the setting of the selector switch on the front panel. These multi-section filters provide a high degree of rejection of all signals other than that in the wanted sideband.

The chosen sideband from the filter is then mixed with the output at 18 kHz from a fixed frequency oscillator in a product detector, thereby converting the signal to audio frequency. The a.f. stage is provided with a gain control, built-in loudspeaker, headphone jack and a number of independent line outputs. H.T. and heater supplies are included in the equipment, making it entirely self-contained.

The -A, -B, -G, and -H versions of the RA63 adaptor are designed to operate on a 100 kHz signal from the i.f. output of the RA.17 / RA.117 or any other suitable high stability communications receiver.

The unit is completely self-contained having its own power supply and a.f. circuits.
It is designed for rack mounting and may be supported by its front panel which is made of 1/8 inch thick aluminium alloy.

Tubes

• Single Sideband Adaptor RA.63 (brochure)       (Publication No. 276-2)