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Racal RA 1792 technical specifications

Racal RA 1792
Frequency Range 150 kHz to 30 MHz
Modes of Reception USB/LSB (R3E, H3E, J3E, R2A, H2A, J2A)
AM (A3E)
CW (A1A)
ISB (B8E) optional
FM (F3E)
Auxiliary - provides demodulated signal centered on optional fixed BFO offset frequency
Tuning Continuously tunable synthesizer in 10 Hz steps over the entire frequency range. Frequency setting either by numerical keypad or by single tuning knob with continuously variable tuning rate from 1 kHz per turn to approximately 20 kHz per turn, depending on the speed of rotation.
Pre-programmed Channels EAROM memory unit may be programmed with up to 100 channel frequencies and mode which may be recalled by keypad or tuning control.
Channel Scanning Automatic scanning of up to ten channels in any decade of the 100 stored channels. Dwell time on each channel variable in ten steps from 0.1 to 10 seconds; pre-selected by numeric keypad.
Frequency Stability Dependent upon frequency standard used:
  1. The following optional internal standard may be supplied:
    1. Temperature Compensated Crystal Oscillator (TCXO): ±2 in 10ºC from -10ºC to +55ºC.
    2. Type 9442:
      1. Temperature: ±3 in 109/ºC
      2. Long term: ±3 in 10 9 per day after 3 months continuous operations.
  2. External standard input: 1 MHz, 5 MHz, or 10 MHz level 0dBm into 50 ohms.
Antenna Input
  1. Wideband, 50 ohms to 75 ohms nominal.
  2. The receiver will withstand without damage input signals of 50 V EMF continuously.
  3. Re-radiation:
    1. 0 to 30 MHz: not greater than 10µV PD.
    2. 30 to 100 MHz: not greater than 200 pW.
  1. CW and SSB (A1A, R2A, A3E, R3E, J3E): In a 3 kHz bandwidth, signal-plus-noise to noise ratio is better than: 150 kHz to 1 MHz: 10 dB with 3 µV (EMF) input, 1 MHz to 30 MHz: 10 dB with 1 µV (EMF) input.
  2. AM (A3E): in a 6 kHz bandwidth, signal-to-noise to noise ratio is better than: 150 kHz to 1 MHz: 10 dB with 10 µV (EMF) input, 70% modulated at 1 kHz, 1 MHz to 30 MHz: 10 dB with 3 µV (EMF) input, 70% modulated at 1 kHz.
IF Selectivity
USB +250 Hz to +3.2 kHz at -6 dB
-400 Hz to -4.3 kHz at -60 dB
LSB +250 Hz to +3.2 kHz at -6 dB
-400 Hz to -4.3 kHz at -60 dB
CW1 300 Hz at -6 dB
3 kHz at -60 dB
CW2 1 kHz at -6 dB
6 kHz at -60 dB
AM1 3.2 kHz at -6 dB
12 kHz at -60 dB
AM2 6.0 kHz at -6 dB
20 kHz at -60 dB
AM3 16 kHz at -6 dB
50 kHz at -60 dB
Note: a maximum of six filters may be installed, in addition to a 16 kHz bypass.
Cross Modulation With a wanted signal of 1 mV EMF in a 3 kHz bandwidth, an unwanted signal 30% modulated removed not less than 20 kHz, must be greater than 500 mV EMF to produce an output 20 dB below the output produced by the wanted signal.
Reciprocal Mixing With wanted signal of less than 100µV EMF in a 3 kHz bandwidth, an unwanted signal more than 20 kHz removed is generally greater than 65 dB above the wanted signal level to give a noise level 20 dB below the output produced by the wanted signal.
Blocking With a wanted signal of 1 mV EMF, an unwanted signal more than 20 kHz removed must be greater than 1 V EMF to reduce the output by 3 dB.
Intermodulation Products In band:
Two 100 mV EMF signals within the IF passband will produce third order intermodulation products not greater than -50 dB relative to the level of either tone at the IF output.

Out of band:
With two 30 mV EMF signals, separated and removed from the wanted signal by not less than 25 kHz, the third order intermodulation products are not less than 90 dB below either of the interfering signals.
Spurious Responses External (including image and IF rejection):
External signals, removed more than 20 kHz from the wanted frequency, must be greater than +80 dB relative to 1 µV EMF to produce an output equal to that produced by a 1 µV EMF signal at the wanted frequency.

The presence of an internally generated spurious response generally will not degrade the specified receiver sensitivity by more than 3 dB.
AGC Range:
An increase in input level of 110 dB above 2 µV EMF will produce an output change of less than 2 dB.

Time constants:
Short, medium and long - preset to be automatically selected by mode switching, but can be set indipendently by pushin-bottons. AGC lines are available at rear of receiver to permit remote control.
IF Gain Control Control range 110 dB:
Gain control may be switched either to manually set receiver gain or AGC threshold.
  1. Variable by main tuning control, ±8 kHz, synthesized in 10 Hz steps
  2. Pre-selected fixed offset may be selected for use with external demodulator.
Pre-set Operating Conditions Bandwidth, AGC time constant and BFO offset may be preset for each mode so that they are automatically recalled when the mode is selected.

'Auxiliary' mode may be set up for any mode, bandwidth, AGC constant and BFO offset. In the ISB mode, diferent AGC time constants may be stored for the two sidebands.
1st LO Output 10 dBm ±3 dBm into 50 ohm load, on read panel.
IF Output 455 kHz, nominal 100 mV into 50 ohms.
Muting 60 dB minimum by grounding rear panel connection.
AF Output
  1. Line output, 10 mW maximum into 600 ohms balanced, adjustable by internal preset level control.
  2. Phone output, 1 mW maximum into 600 ohms unbalanced.
  3. 200 mW maximum to internal loudspeaker which may be switched in or out of operation.
  4. Connection for external loudspeaker, 200 mW into 16 ohms; 400 mW into 8 ohms.
Metering Front panel display switched to indicate RF level or AF level output to line
BITE All measured supply voltages to be within ±20%

Varactor line voltage: -
20 MHz Reference Loop: 6 to 11 V DC
BFO Synthesizer: 8 V ±0.5 V DC
LO Synthesizer: 3.5 to 15 V
Power Supply AC: Selections for 110, 120, 220 oer 240 V operation; +10% -15%. 45 to 65 Hz

DC: Receiver may also be operated from an 18 to 32 V DC source when receiver is equipped with optional DC power supply.
Power Consumption Approximately 60 VA for AC operation; approximately 40 Watts for DC operation.
Display Illumination Presettable.
Environmental Conditions
  1. The equipment is designed to operate under the following climatic conditions:
    Operating temperature -10ºC to +55ºC
    Storage temperature -40ºC to +70ºC
    Relative humidity 95% at +40ºC
  2. The equipment is suitable for mobile operation.
  3. The equipment is suitable for air transportation in unpressurized conditions and for operation up to altitudes of 3500 metres above the sea level.
Dimensions Height - 133 mm (5.29 in)
Width - 483 mm (19 in.)
Depth - 458 mm (18 in.)
Weight 14 kg (31 lbs.)

Radio Emission Codes

Radio Emission Codes are specified using three symbols as shown below:
First symbol - Type of modulation of main carrier
Second symbol - Nature of modulating signal
Third symbol - Nature of transmitted signal

The principal symbols are listed below:
First Symbol Type of Modulation
Double sideband, AM
Indipendent sideband, AM
Vestigial sideband, AM
Amplitude/Angle modulation
Frequency modulation
Phase modulation
Single sideband full carrier
Single sideband suppressed carrier
Pulses, amplitude modulated
Pulses, width or duration modulated
Pulses, phase or position modulated
Unmodulated carrier
Pulses, unmodulated
Single side band reduced or variable carrier
Second Symbol Nature of Modulating Signal
No modulation signal
On/Off modulation (keyed CW)
Modulation sub carrier (keyed MCW)
Analogue modulation (voice)
Two or more channels on one frequency offering keyed telegraphy
Two or more channels on one frequency offering telephony (voice)
Third Symbol Type of Information Being Transmitted
Telegraphy for aural reception
Telegraphy for automatic reception

All data from the original Maintenance Manual of HF Receiver RA 1792 (83000, 82129 and 85830) edited by
Racal Communications Limited, Western Road, Bracknell, RG121RG england, Ref TH 3416.

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