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Remote Controllable Directional AM Antenna Monitor


Model CMR

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The Model CMR is a state of the art instrument with unequalled accuracy and stability, at a price comparable with analog monitors. With typical modulation, the CMR’s true ratio readout is a factor of 10 more stable than instruments that measure normalized amplitude, and its phase readout is rock solid. Phase sign is automatic; no extra operation. Practically, these features mean quick, accurate log or remote readings. The CMR is fully remoteable via land or telemetry, using standard remote control equipment. An optional repeater-controller is available for hardwire remote control and readout via multiconductor cable at distances up to 1500 feet.

The CMR’s outstanding performance and reasonable price make it ideal for new DA installations or for modernizing the instrumentation of existing stations.

  • True Ratio reading. Non-Reference and Reference amplitudes are separately measured and divided electronically to give an accurate digital reading (and an equally accurate D.C. voltage for remote readings) that will not vary with carrier level, and is exceptionally stable under conditions of deep, unsymmetric modulation
  • Stable, accurate phase reading with automatic phase sign.
  • Amplitude or True Ratio may be selected for measurement with a front panel switch . Optional common point terminal for measuring common point amplitude.
  • Designed for Reliability and Maintainability. MIL Spec. PC boards with plated through holes. Gold plated switch and relay contacts. Relays have been tested to 10 to the seventh operations without failing. All ICs and relays are socketed. Each unit is burned in at least one week to expose early IC failure.
  • Dual Surge Protection. Gas Discharge tubes across the sample line terminations, plus a relay that drops out when the monitor is not being interrogated and disconnects the sample lines from the electronics, protect against lighting induced sample line surges.
  • LEVEL Meter simplifies installation.
  • Accurate. Typically exceeds FCC specs. by substantial margins.
  • Narrow phase – sign ambiguity (typically, +0.1 degrees) give accurate phase readings near zero or 180 degrees.
  • One year warranty.


  • Frequency range: 500 – 2000 khz.
  • Up to six towers, DA1 or DA2.
  • 50 or 75 ohm terminations, N or UHF sample line receptacles.
  • Ratio:
    range – 0 – 1.999
    resolution – .001
    accuracy – typical .5% or better. FCC spec.; 2% for ratios from .5 to 1.0, 5% for ratios from .2 to .5.
    D.C. output for remote reading via telemetry or phone line – max. voltage; 4.5 VDC for ratios of 1.999. Linearity .5% or better. Minimum load, 4000 ohms.
  • Phase:
    range – 0 to +/-180 degrees
    resolution – 0.1 degrees
    accuracy – typically 0.5 degrees or better. FCC Spec.; 2 degrees for ratios from .2 to .5, 1 degrees for ratios from .5 to 1.0.D.C output for remote reading via telemetry or phone line – max. voltage; 5 VDC for 180 degrees phase. Linearity .3% or better. Minimum load 4000 ohms.
    Phase sign – automatic display. TTL level output for remote reading.
  • Remote Tower Selection; – by means of external contact closures – max. contact current 60 ma. DC.
  • Sample Signal Range; 1.8-15 VRMS.
  • Power – 108-132 V., 6 Watts, 50-60 hz.
  • Temperature – 0-50 degree C.
  • Display Blanking – automatic when monitor is not being interrogated.
  • BCD output. Multiplexed, at TTL levels with 1 TTL load fanout. Four BCD lines, Four Digit Select Lines, one parameter select line, one phase sign line. (Intended for use with CMR – 1 remote controller – repeater.)
  • Dimension – 19″ Rack mount, 5 1/4″ high, 6 1/2″ deep. LED readout are 1/2″ high.
  • Common point input (amplitude readout regardless of Ratio-Amplitude switch setting)
  • To order specify number of towers, number patterns, sample line impedance, and type of connector on sample line at monitor end (type N or UHF). Also
    please supply operating frequency.
    Cable to interconnect remote control equipment.

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