851S-1 Receiver


THE COLLINS 851S-1 Receiver

The Rockwell-Collins 851S-1 Receiver (Collins PN 622-4272- XXX) is the latest offering in our expanding line of user-oriented receiver products. The 851S-1 features continuous rate sensitive tuning.

Versatility and growth capability are offered through many available options such as variable BFO, automatic frequency control, presets, and remote control. These options permit user configuration of the 851S-1 to satisfy individual system and mission requirements. Fast synthesizer channeling time and flexible remote control formats further enhance the receiver's capability. The companion remote control unit, HF-8095, provides true continuous tuning with the feel and characteristics of the 851S-1 receiver.

The 851S-1 receiver provides 100 Hz (10 Hz optional) incremental coverage of the 0.250 to 29.99999 MHz frequency range. Extended coverage down to 12 kHz is possible with installation of the VLF module. The triple-conversion signal translation scheme provides clean and spurious free operation with excellent if and image rejection. In its basic configuration of USB or LSB (A3J), CW (A1) and AM (A3/A3H) operation, the 851S-1 makes an excellent manually controlled surveillance receiver either for a receive-only site or a full communications station.

In-station use is not an operational restriction on the 851S-1. Conversion from an 851S-1 local control receiver to an 851S-1 FSK or RS-232C(CCITT V.24)/MIL-STD-188C remote controlled receiver is done by a simple 3-card addition. An 851S-1 can be remotely controlled by an HF-8095 Remote Control Unit up to 8 km (5 miles) over field wire, or unlimited distances over standard telephone circuits or radio links with the FSK interface. Using the RS-232C (CCITT V.24) strapping on the interface cards allows external modems and processors and voice grade lines to be used for controlling multiple receivers. Such a system can control up to 16 receivers per control bus. Optional 10 Hz tuning increment capability is available for fine tuning by remote control.

A selection of other user-installed circuit cards are available to expand the performance features and increase the versatility of the receivers. Various bandwidth if filters may be added to complement the standard 2.7 kHz sideband and 16 kHz AM filters, internal oven standard or provisions for an external standard to replace the temperature-compensated crystal oscillator. Additional options which may be added to the 851S-1 include phase-locked digital variable BFO, ISB, 10 Hz tuning increments, automatic frequency control, preset channels, and half-octave filters.

Design and Performance Specifications

The 851S-1 was designed in accordance with the requirements of the following documents:
International Telecommunications Union (ITU) - Radio Regulations.
International Radio Consultants Committee (CCIR) - Performance Recommendations of the XII Plenary Assembly.
Electronics Industries Association (EIA) Standard RS-232C - Data Interfaces.
Comite Consultatif Iternationale Telegraphic et Telephonie (CCITT) re V.24 - Data Interfaces.
Military Standard 188C - Data Characteristics.
Military Standard 810C - Environmental Test Methods.

Options and Accessories

A group of options and accessories has been chosen to facilitate installation, operation, and maintenance. Collins is prepared to suggest those options and accessories that will be useful in the customer's installation and that will work directly in the system without requiring attritional interface units. Recommendations can also be made for other items not normally listed, but which may be desired in a unique system installation.

IF Filters
Up to five additional mechanical or crystal filters can be added to the receivers. Implementation is by a simple plug-in card. Stick-on decals, supplied with the optional filters, can be placed at the bandwidth switch position marks on the front panel for filter identification.

External Standard
This standard enables the receivers to be operated from a 100 kHz, 1 MHz, or 5 MHz external frequency source of desired stability. Implementation is by plug-in module substitution and the addition of an RF connector on the rear of the chassis.

Oven Standard
This is an internal oven frequency standard with a stability of 1 x 10-8 over the specified operating temperature range. Implementation is by simple plug-in module substitution.

Frequency Standard Switch
This module enables the receiver to operate from an external frequency source or from an internal oven standard. When an external reference (100 kHz, 1 MHz, 5 MHz) is applied, the synthesizer is locked to this reference. Should the external reference malfunction or the signal be interrupted, the frequency standard switch automatically switches to the internal standard, preventing loss of lock. A 100 kHz reference output is provided from the frequency standard switch to the rear panel.

10 Hz Tuning Increments
Expansion of the frequency tuning increments from the standard 100 Hz steps to 10 Hz steps is by addition of a plug-in module to the synthesizer and modification to the frequency display.

Remote Control
The remote control option is implemented in the 851S-1 receiver by the addition of three plug-in circuit cards. The option provides serial remote control of the receiver from the HF-8095 accessory remote control, or from a remote processor. User selectable parameters include selection of FSK, EIA RS-232C (CCITT V.24), or MIL-STD-188C compatible signalling levels. Serial control data rates are also selectable between 75 and 19,200 baud (75 to 600 baud for the FSK signalling method). The remote control serial data format is based on asynchronous eight-bit (byte) data characters and provides for addressing up to sixteen receivers connected to a co on data bus. An additional user selectable seven-bit (USASCII) data character format for remote processor control applications is also available

Independent Sideband (ISB)
The 851S-1 may be configured for ISB reception by the addition of the channel B IF amplifier. In the ISB mode, the lower sideband (LSB) signal is processed by the channel B IF. The LSB 450 kHz will be available at the rear panel and the LSB audio becomes channel B audio (line, headphone, speaker).

Half-Octave Filters
Additional front-end selectivity may be obtained through the use of 10 half-octave filters. The frequency bands are: 0 to 0.56 MHz, 0.56 to 2.0 MHz, 2.0 to 3.0 MHz, 3.0 to 4.0 MHz, 4.0 to 6.0 MHz, 6.0 to 8.0 MHz, 8.0 to 12.0 MHz, 12.0 to 16.0 MHz, 16.0 to 24.0 MHz, and 24.0 to 30.0 MHz.

Digital Variable Beat Frequency Oscillator (DVBFO)
The DVBFO is a synthesized, phase-locked oscillator which provides a variable injection to the IF product detector. Tuned from the front panel, the VBFO offset range is +/-9.99 kHz in 10 Hz steps. Typical applications include tuning of narrow CW filters and teletypewriter configurations.

Automatic Frequency Control (AFC)
The APC card enables the receiver to lock to and track a carrier frequency. When enabled, a carrier within +50 Hz of the tuned frequency will be captured by the receiver. This carrier may then be tracked +/-1 kHz from the tuned frequency provided that the carrier does not shift more than 10 Hz per second. The AFC function is intended to be used with carrier suppression of not more than 20 dB below pep.

Preset Channels
The preset option provides sixteen channels of preset frequency and mode parameters which may be quickly selected with a front panel preset channel select switch. The preset channel parameters are user-programmable from the 851S-1 front panel controls, and are stored in nonvolatile semiconductor memory for retention during power off periods of one year or longer. When configured with the preset option, the remote control option cannot be implemented in the 851S-1 receiver. For remote control preset operation of the receiver, the preset option may be installed in the HF-8095 accessory remote control, with the 851S-1 equipped with the remote control option.

VLF Translator
The VLF Translator module extends the small signal sensitivity performance of the standard translator down to 12 kHz (vlf/lf).


The HF-8095 Control, Receiver, Collins PN 622-3489-001 permits complete frequency, mode, bandwidth, RF gain, AGC, and ISB audio channel remote control of up to 16 851S-1 Receivers. Monitor information (frequency, mode, bandwidth, fault summary) is provided and displayed on the control front panel. Control is by four-wire, voice grade communication line with unlimited distances, depending on line characteristics. Control is complete with FSK modem, ready for connection to communication line for single receiver control. Control output can also be strapped for EIA RS-232C (CCITT V.24) or MIL-STD-188C data characteristics for use with external modems (and processors) to control multiple receivers. The HF-8060 Preselector, Collins PN 622-3386-001, is an automatically tuned bandpass filter. It provides front-end selectivity and overload protection as well as improving cross modulation and out-of-band intermodulation performance.

The CA-8010 Desk Top Cabinet, Collins PN 622-3416-001, is a desk top mounting enclosure for 851S-1 Receiver and HF-8095 controls. It has standard EIA mounting characteristics and includes fold down tilt stand. Size: 210 mm (8.3 in) h, 536 mm (21.1 in) w and 457 mm (18 in) d. Weight: 6.8 kg (15 Lb). Color: gray.

Headphones and Headsets
The AC-8050 Standard Headphones, Collins PN 622-3412-001, are standard headphones with 600-ohm impedance, equipped with sound blocking ear muffs.

The AC-8051 Lightweight Headphones, Collins PN 622-3413-001, have 500-ohm impedance and comfort designed ear pieces.

Special Test Accessories
The TS-8010 Card Extender Kit, Collins PN 622-3431-001, provides adapters to extend cards and modules beyond the chassis for power-on troubleshooting.


The following patents cover advanced design techniques used in this receiver:
Proportional Digital Control for Radio Frequency Synthesizer - Max Peterson - Patent Number 3,665,323
Digitalized Frequency and Phase Discriminator - John Andrea - Patent Number 3,431,509

Under the hood...

[Inside View]


  Size .................... 178 mm high, 483 mm wide, 531 mm deep 
                            (7 in. high x 19 in. wide x 20.9 in. deep).

  Weight .................. 17.2 kg (38 lb).


  Temperature ............. 0 to 50 C (+32 to +122 F), full performance;
                            -20 to 0 C (-4 to +32 F), reduced performance;
                            -57 to +70 C (-71 to +158 F), nonoperating.

  Humidity ................ MIL-STD-810C, Procedure II, figure 507.1-2;
                            two 48-hour cycles of 0 to 95 percent,
                            0 to 50 C, without condensation.

  Altitude ...............  Up to 3660 m (12,000 ft), operating.
                            Up to 12,190 m (40,000 ft), nonoperating.

  Shock ..................  Bench handling - MIL-STD-810C, Procedure V,
                            method 516.2. Transportable - MIL-STD-810C,
                            Procedure 1, method 516.2, figure 516.2-2; 15 g
                            duration 11 milliseconds, three shocks in each
                            of all three planes.

  Vibration ..............  1.5 g, 5.5 to 55 Hz - MIL-STD-810C, proc X,
                            method 514.2.


  Modes of operation .....  A3J (USB or LSB), A3/A3H (AME), A1 (CW), and
                            optional A3B/A9B (ISB).

  Frequency coverage .....  250.D kHz up to 29.99999 MHz. Low end sensitivity
                            specified at 250 kHz. Usable to 15 kHz with
                            reduced sensitivity.

  Frequency stability ....  Not less than 5 x 10-7 over specified temperature.
                            Drift rate of not more than 3 x 10-8 per week.
                            Optional oven standard provides not less than
                            1 x 10-8 over specified temperature.
                            External standard option provides stability of the
                            100 kHz, 1 MHz, or 5 MHz external standard used.

  Tune increments ........  100 Hz with optional 10 Hz.

  Channeling speed .......  2 ms, nominal; 5 ms, max.

  DVBFO ..................  Optional +/-9.99 kHz in 10 Hz steps.

  Sensitivity (SSB) ......  0.25 to 1.6 MHz, 2 uV "hard" for 10 dB (s+n)/n;
                            1.6 to 29.9 MHz, 0.7 uV "hard" for 10 dB (s+n)/n.

  Intermod distortion ....  In band, -40 dB from either of two input tones,
                            0.1 V per tone. Out of band, 2nd and 3rd order,
                            -80 dB from either of two input signals, 10 mV
                            per tone, 50 kHz or more off center frequency.

  Spurious responses .....  Less than 0.5 uV "hard" equivalent input signal,
  to internal signals       1.6 to 29.9999 MHz.

  Spurious responses .....  IF rejection -90 dB min. Image rejection -90 dB
  to external signals       min. Other spurious -80 dB min at 20 kHz or more
                            off center frequency.

  Audio outputs ..........  Line: 600 ohms 10%, bal; 0 dBm, nom; adj,
                            -20 to +10 dBm.
                            Headphone: 600 ohms, nom; +10 dBm min.
                            Speaker: 8 ohms, nom; 2 watts, min.

  Audio hum ant noise ..... -40 dB on line audio output.

  Gain .................... 0 dBm line audio out for 3 uV input, SSB mode.

  AGC threshold ........... 3 uV max.

  AGC control ............. 6 dB max rise in audio out for signal increase
                            from 3 uV to 0.3 V.

  AGC time constants ...... 5 ms nominal, attack. 0.1-second fast decay and
                            1-second slow decay.

  Squelch ................. Operates on audio signal-to-noise ratio.
                            Applicable only to speaker output.

  IF output ............... 20 mV at 450 kHz into 50 ohms for 3 uV input

  Bandwidths .............. 16 kHz, 2.7 kHz USB, and 2.7 kHz LSB, or 3.2 kHz
                            USB, and 3.2 kHz LSB. Optional add-on filters
                            include 6.0, 3.0, 1.0, 0.5, and 0.2 kHz.

Antenna input impedance ... 50 ohms, nom; unbalanced.

Rf overload protection .... Up to 100 V rf input, power on or off.

Primary power ............. 115/230 V ac +10%, single phase, 47 to 420 Hz;
                            80 watts, max.

Duty cycle ................ Continuous.

Rf input filter ........... Standard: LC rf input filters, (3 bands).
                            Optional: half-octave LC filters, (10 bands).

Rf preselector ............ Optional: Use of HF-8060 preselector provides
                            additional front-end selectivity and overload
                            Selectivity: Not less than 47 dB at +/-10% from
                            tuned frequency.
                            Overload Protection: Protected up to 500 volts 

Remote control ............ Optional: The 851S-1 may be remote controlled.
                            Interfaces are either FSK or RS-232C
                            (CCITT V.24)/MIL-STD-188C.

Block Diagram...

[Block Diagram]


The 851S-1 is a desk-top or rack-mounted receiver featuring solid-state design. It mounts in a standard EIA 483 mm (19-inch) rack or in an optional desk-top cabinet. Provisions are made for slide mounting as an option.

All controls for manual operation are located on the front panel. A rotary tuning control provides for frequency selection, and toggle switches allow selection of AGC time, speaker channel, and local or remote control. Controls are provided for audio gain, headphone channel, squelch, RF gain, bandwidth, mode, and meter monitor. The power on/off switch is a pushbutton type. The selected frequency and optional VBFO offset frequency are displayed by a large (0.3 in) red-orange LED display. A front panel meter monitors audio line levels and rf input signal level. LED indicators provide visual indications of equipment fault, rf overload, and preselector fault and overload conditions. A front panel speaker and headphone jack are also provided.

The 851S-1 construction consists of a main chassis with card cage subassembly, utilizing plug-in modules. Adequate testpoints are provided on the modules to aid troubleshooting. Dust covers are provided to allow rapid access for maintenance. The dust covers allow air circulation and all cooling is by natural convection and conduction.

The receiver maximizes the use of ribbon cable and printed circuit interconnect. All external electrical connections (except for front panel headphones) are made at the rear connectors and terminal strips.

Refer to functional block diagram.

The primary function of the 851S-1 receiver is to receive rf signals and process them into audio signals. The standard configuration provides 100 Hz incremental coverage of the 0.250 to 29.99999 MHz frequency range (usable to 15 kHz with reduced sensitivity) in the USB, LSB, CW, and AM modes.

The continuous tuning scheme uses a Rockwell-Collins patented optical tuning switch to generate direction and rate of tuning. This information is decoded and supplied to the fast tune synthesizer, which then provides the proper injection signals. The combination of 100 Hz (10 Hz optional) tune increments and a fast tune synthesizer gives the operator a sense of continuous frequency tuning.

The receiver input signal is passed from the antenna through a low-pass filter and routed to one of the three diode switched bandpass filters. After bandpass filtering, the signal is routed through an AGC controlled attenuator stage and a series low-pass filter to a balanced grounded gate FET mixer. The signal is mixed with a variable injection frequency signal from the synthesizer of from 79.35 to 109.35 MHz. The frequency of this variable injection signal is based upon the selected operating frequency to produce the 109.35 MHz first conversion if signal.

The 109.35 MHz signal is amplified and passed through a 109.35 MHz crystal filter (with 16 kHz bandwidth). The filtered signal is amplified and applied to a second mixer. At this stage, the 109.35 MHz signal is mixed with a 118.8 MHz fixed injection signal from the synthesizer to produce a 9.45 MHz second conversion if signal. This signal is amplified, passed through an AGC controlled attenuator stage and then further amplified. The signal is then applied through a 9.45 MHz crystal filter (with 16 kHz bandwidth) to a third mixer.

The 9.45 MHz if signal is mixed with a 9.9 MHz fixed injection signal from the synthesizer to produce 450 kHz third (final) conversion if signal. The 450 kHz signal is then applied through one of two (or both in ISB) 450 kHz mechanical sideband filters (2.7 or 3.2 kHz bandwidth) or a pad if 16-kHz bandwidth is desired. Various optional if bandwidth filters are available if other operating bandwidths are desired.

The 450-kHz signal is then amplified in an amplifier where if AGC is applied to control the receiver gain. The IF signal path is branched and routed to a connector on the rear chassis, applied to an SB/CW audio detection circuit or to an AM/AGC detection circuit.

The single sideband or CW signal is applied with the 450 kHz BFO signal to the product detector to produce an audio signal. The optional VBFO may be used in place of the fixed 450 kHz injection in the SSB/CW mode. The desired offset is tuned from the front panel covering a range of +/-9.99 kHz in 10 Hz increments and is phase-locked to the frequency standard. The IF signal is demodulated by an emitter follower envelope detector to produce AM audio and AGC.

When the optional ISB mode is selected, USB and LSB signals are simultaneously received and processed. The channel A (USB) AGC detector develops an RF AGC voltage which is applied, along with another RF AGC voltage developed by the channel B (LSB) AGC detector, to the 109.35 MHz mixer and to the 10.35 MHz IF amplifier. These two AGC signals represent the relative strengths of the USB and LSB signals. The AGC produced by the stronger signal predominates and automatically adjust the receiver front-end circuits for both USB and LSB reception. Independent AGC circuits control the USB and LSB signals at the IF frequency to produce maximum signal intelligibility.

All the audio signals are applied to the audio amplifier and gating circuits. Specific enable signals determine which audio signal (mode) is to be amplified, AM enable, CW enable, etc. The audio is amplified and an output from a 600-ohm audio output transformer is applied to a rear chassis terminal strip. Audio is also applied through the front panel volume control (AF gain) to a speaker amplifier circuit. This signal is amplified to provide a 2-W average output into an 8-ohm speaker. A separate output is available for headphones.

Part of the audio output is also applied to a squelch control circuit. Active filters and signal/noise detectors sense the amount of noise (high-frequency components) and signal (low-frequency components) in the audio signal. The outputs of the detectors are compared in a signal/noise comparator. A predominance of high-frequency noise will activate threshold detectors, which generate a muting control for the speaker. The squelch threshold may be adjusted with a front panel control. The squelch circuitry applies to the speaker output only and does not include the line audio or headphone outputs.

Overall gain of the receiver may be controlled by the front- panel RF gain control. This analog voltage is applied to both the RF and IF sections of the receiver.

The control interface permits remote serial control and monitoring of the 851S-1 by an HF-8095 Remote Control Unit. The interface will receive and transmit FSK data or data at logic levels compatible with EIA Standard RS-232C (CCITT V.24) or MIL-STD-188C.

The interface circuits perform serial/parallel, parallel/serial data conversions and interface directly to the serial control and monitor data buses. The card accepts parallel monitor data from the receiver and transmits the data in serial form to the control unit or accepts serial command data from the control unit and transforms it into parallel data to control the receiver.

The parallel output latches are tri-state devices which can be placed in the disabled state (high output impedance) when the receiver is in "local" control mode. In local control mode, the front panel controls, which are connected in parallel with the parallel output card lines, will be activated to control equipment functions.

An RF overload protection circuit is incorporated on the antenna input line. The circuit monitors the rf present on the input and if it approaches a level that would cause damage to the receiver, a relay is opened to disconnect the receiver from the antenna. The circuit is automatically reset on removal of the strong signal. The occurrence of an overload condition illuminates the front panel "RF OVERLOAD" indicator. When prime power is removed, the antenna input is open circuit.

Performance monitor data is provided in the remote control word format. These monitors may be used to monitor receiver operation and isolate fault conditions when they occur. Functions covered by the performance monitors include: AGC and audio performance, AFC lock, frequency and VBFO synthesizer fault, power supply fault, and receiver and/or preselector overload.

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Most recent revision Sunday, June 18, 2000