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MSR-904A
Precision surveillance receiver - under construction

MSR-904 is a precision VHF-SHF surveillance receiver for signals between 30 MHz 1 and 18 GHz, optionally expandable 2 to 40 GHz, developed around 1982 by Micro-Tel in Huntsville (MD, USA). It succeeded the MSR-903 receiver and was intended for interception of microwave links, satellite downlinks, telemetry signals, bugs, etc. The MSR-904A is an enhanced version of the MSR-904.

The receiver is housed in a 19" rackmountable enclosure with strong grips and the front and at the rear. The well-organised control panel is painted in the typical Micro-Tel mint colour.

Most functions are controlled by push-buttons rather than by rotatory selectors, and a digital frequency readout is available at the right. At the left is a small CRT that offers a panoramic view of the spectrum around the selected frequency. Two fast-responding LED bars are used as signal strength and tuning indicators. The frequency is set with the large dual-speed dial at the right.
  
Micro-Tel MSR-904A surveillance receiver

...

  1. Requires option (3).
  2. Requires option (8) and external FE-904 frequency extender.

Micro-Tel MSR-904A surveillance receiver Micro-Tel MSR-9044 surveillance receiver MSR-904A front panel MSR-904A Rear panel
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Micro-Tel MSR-904A surveillance receiver
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Micro-Tel MSR-9044 surveillance receiver
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MSR-904A front panel
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MSR-904A Rear panel

Controls
The diagram below shows the front panel of the MSR-904A, which is divided into three sections: the panaramic display and the attenuator at the left, the controls at the center and the tuning dial with frequency readout at the right. The power switch is at the bottom left. A suitable pair of headphones should be connected at the bottom right, where also the AM/FM selection is located.


The MSR-904 is the first receiver that does not feature the typical rotary selectors for band, bandwidth, scanning, etc. Instead, the functions are selected by means of neatly arranged push-buttons with a built-in LED indicator. The scanning mode is also selected with push-buttons, whilst the scanning adjustments are made with the five knobs along the bottom edge.


All connections (except for the headphones) are at the rear side. The AC mains should be connected to the 3-pin military socket to the right of the fan. Select the appropriate mains voltage before connecting the receiver to the mains. At the top left are the two antenna inputs (here protected with a red plastic cap). At the top right are the IF outputs and additional output for driving an external oscilloscope. Various sockets are available for remote control purposes.


Interior
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Restoration
...

Specifications
  • Frequency
     see frequency bands
  • Noise
    20-22 dB
  • Readout
    5-digit LED display, 1 MHz resolution, accuracy ±1%
  • Tuning
    Electronic
  • Modes
     see tuning modes
  • Preselection
    ≥ 500 MHz: tracked YIG filter, < 500 MHz: low-pass filter
  • Tuning indicator
    9-segment LED bar
  • 3rd order intercept
    +5dBm
  • AFC
    10:1 correction
  • Signal indicator
    10-segment LED bar
  • LO antenna leakage
    ≤-70dBm (above 12 GHz: ≤-60dBm)
  • RFI
    Fully RFI-shielded
  • Image rejection
    >70dB, 60dB above 12 GHz
  • IF rejection
    >80dB
  • LO sample
    -10dBm nominal
  • RF inputs
    Type N, 50Ω nominal
  • IF gain control
    60dB range (automatic or manual)
  • IF bandwidths
    0.1, 1, 5, 30 MHz (other bandwidths optionally available)
  • IF attenuator
    99dB in 1dB steps
  • IF reference
    RF level measurement to ±1dB accuracy with calibration chart
  • Demodulator outputs
    AM (2Vpp 50Ω), FM (2Vpp 50Ω), Audio (5mW 600Ω)
  • Oscilloscope
    Hor: 3Vpp DC 1000&Omega. Blanking: +5V pulse at 5000Ω
  • Digital control
    Parallel data, TTL compatible (frequency, band, mode, etc.)
  • Power
    115/230V AC ±10%, 50-400 Hz, 120W
  • Temperature
    0-50°C
  • Size
    19 x 17 x 5¼ inches
  • Weight
    40 pounds
Frequency bands
  1. 30 MHz - 500 MHz
    Requires option (3)
  2. 500 MHz - 18 GHz
    Standard
  3. 18-26 GHz
    Requires option (8) and external FE-904
  4. 26-40 GHz
    Requires option (8) and external FE-904
IF outputs
  • 250 MHz
    Remote tuner output: 40 MHz bandwidth, ≤+5dBm
  • 160 MHz
    Internal 250/160 MHz convertor, may be phase locked. BW: 20 MHz 1
  • 70 MHz
    Output at rear 2
  • 21.4 MHz
    Leveled output, -20dBm ±3, dynamic range 50dB
  1. Requires option (4B).
  2. Requires option (4C).

Tuning modes
  • CW
    Duals-speed frequency control
  • ΔF0
    Variable, 0 to ±5% around current center frequency
  • F1-F2
    Scan between F1 and F2, variable marker
  • Band
    Scan of push-button selected band with frequency marker
  • Ext
    External tuning voltage input (0-10V)
Options
  • 1
    MSR-904A receiver (500 MHz - 18 GHz)
  • 2
    LO sample for synthesizers or counters
  • 3
    Low frequency Coverage 30 MHz - 500 MHz
  • 4A 1
    21.4 MHz IF output
  • 4B
    160 MHz IF output, phase lockable with synthesizer
  • 4C
    70 MHz IF output, phase lockable with synthesizer
  • 5
    Special IF bandwidths (custom)
  • 6
    IF reference, measure RF amplitude to 1dB with calibration chart
  • 7 1
    Auto-stop
  • 8
    Provision for 18-40 GHz
  1. Standard on MSR-904A (ordered separately on MSR-904).

Add-ons
  • AP-904
    Antenna pre-amplifier 30 MHz - 18 GHz 1
  • FE-904
    Frequency extender 18-26 GHz and/or 26-40 GHz
  • DC-904
    Digitally refreshed CRT
  • FCS-904
    Frequency counter/synthesizer
  • MPC-1100
    Computer controller
  • IO-1000-904
    IEEE-488 bus interface unit
  1. Requires option (8) for MSR-904A.

Documentation
  1. MSR-904A - 0.03-18 GHz digitally controllable microwave surveillance receiver
    Brochure. Micro-Tel (Adams-Russel). February 1989. 1

  2. MSR-904A - Specifications
    Micro-Tel. Date unknown. 1

  3. Operating and maintenance manual for Micro-Tel MSR-904A
    Micro-Tel (Adams-Russel). April 1983. 2 parts.

  4. Operating and service manual for Micro-Tel MSR-904A
    Micro-Tel (Adams-Russel). September 1983. 3 parts.
  1. Obtained via Terry O'Laughlin, Black Radios website.  More

References
  1. Simon Schrödle, Micro-Tel MSR-904A microwave receiver
    Website: Simons Dialogs, September 2014.
Further information
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Crypto Museum. Created: Tuesday 17 October 2017. Last changed: Tuesday, 24 October 2017 - 05:28 CET.
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