MR4 Receiver

    Commercial Amateur
135-174 MHz
215-250 MHz
420-520 MHz
MR4 Receiver (installed internally)
$675.00 USD
$675.00 USD
$675.00 USD
$685.00 USD
$525.00 USD
$525.00 USD
$525.00 USD
$630.00 USD


The same receiver as our famous MR4 Rack Mount with out the mounting panel and metering.

MR4 Features

  • 7 large helical resonators for outstanding overload performance
  • Double conversion with 21.4 MHz first IF for 120 DB image rejection
  • 12-pole crystal and ceramic IF filter
  • Automatic fast / slow squelch virtually eliminates squelch tail
  • Squelch hysteresis follows fading signals
  • Shielded oscillator / multiplier chain
  • Metering circuits for signal strength, peak deviation, and discrimination
  • Silver mica and mylar capacitors hold peak performance over temperature
  • Provision for internal CTCSS decoder
  • Feedback and Q-damping insures optimum performance over time and temperature


Radio channels are crowded enough today - tomorrow the congestion will be even worse. That is why every type of the MR4 R is designed for outstanding performance in the harshest RF environments. With 7 large helical filters in the front-end and 12 poles of IF filtering the MR4 R is immune to de-sense at interference levels greater than 100,000 uv. Two of the resonators are placed ahead of the RF pre- amplifier for exceptional overload resistance. The 21.4 MHz first IF and shielded oscillator / multiplier chain make it difficult to even measure an image, and its double balanced first and second mixers reject inter modulation products by 80 DB. Feedback, damped-Q tuned circuits and decoupling are used so that gain stages operate conservatively not wide open. NPO and mylar capacitors keep the performance consistently high over temperature extremes.

The MR4 R is also packed with operational features like our famous MCS squelch circuit that is often called "The Best There Is." Now we have added automatic fast/slow squelch to lock in on weak signals and virtually eliminate squelch tails on strong signals. Full metering provisions for signal strength, deviation, and discrimination are included as are line and local speaker audio outputs.

Compare the MR4 specs with those of any other receiver - there is no Competition!

  • Specifications
    Frequency Range
    216-250MHZ (VHF)
    420-512MHz (UHF)

  • Sensitivity
    .25-.35 uv (typ.) for 12DB SINAD

  • Selectivity
    -6DB at + 6.5KHz -105DB at + 15KHz -125DB at +25KHz

  • Spurious and Image Response
    -85DB Spurious -125DB Image

  • Overload / De-sense 75,000 uv + 600KHz (VHF)
    100,000 uv + 2MHz (VHF)
    75,000 uv + 2MHz (UHF)
    100,000 uv + 5MHz (UHF)

  • Inter-modulation -80DB (EIA method)

  • I.F.
    21.4MHz first 455KHz second

  • I.F. Filtering
    8-pole crystal at 21.4MHZ 4-pole ceramic at 455KHz (optional 9-pole ceramic)

  • First Oscillator Stability
    +.0005% (-10 to +60C) + .0002% with optional oven

  • Squelch Circuit
    Schmitt trigger with 6DB hysteresis

  • Squelch Threshold
    .1-.15 uv, automatic switch to fast mode with signals greater than 10uV

  • Modulation Acceptance
    + 7KHz

  • Audio De-emphasis
    -6DB / octave (EIA)

  • Audio Output
    1.5W into 4ohms (local) 0.4Vrms,1000ohms (line / repeat)

  • External Controls
    50Kohms squelch - 100ohms local audio

  • External Metering
    0-1mA, 2300ohms for each function

  • COS Output
    open collector, selectable active high or factory set active low

  • Voltage Required
    13VDC nominal (11-14VDC limit)

  • Current Drain
    180ma squelched 200ma nominal un-squelched 250ma with full audio output

  • Crystal specification
    136-151MHz Fx = (Fo-21.4MHz)
    2 151-174MHz Fx = (Fo-21.4MHz)
    3 216-250MHz Fx = (Fo-21.4MHz)
    4 420-512MHz Fx = (Fo-21.4MHz)
    8 Parallel resonant, third overtone, resistance 30ohms max. 12pF load capacity, HC-25/U case

  • Physical (modular version)
    5" x 7.25" x 2.5" enclosure w/feed-thru capacitors & UHF connector

  • Physical (rack version)
    19" x 5.25" rack panel, 5" deep includes meters, controls, and speaker
  • Warranty

  • All ACS products are guaranteed in materials and workmanship for 1 year from the date of purchase. Please contact us for complete details.

Specifications are subject to change without notice.

MR4 R receivers are factory tested, aligned, and tuned to your frequency before shipment. They are engineered to give years of reliable service with no periodic adjustment or maintenance.


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