Potomac Instruments 1900 Series – Digital Antenna Monitors




There are three different units in the 1900 Series. The basic unit is the Model 1901.This 5 1/4 inch unit contains control/measurement circuitry for up to 12 towers, digital display of all measurements, local operating controls, and an interface to a remote control system. The control/measurement circuitry for each tower is contained in a separate module. The modules plug into the rear of the unit, and may be easily added to an expanding station.

Simplified Operation

The operating controls are identical for the 1901 and 1902 models. The monitoring system is controlled with four pushbuttons, three are located to the left of the display and one to the right. The first pushbutton is used to select one of three different modes. The RATIO mode displays the true ratio of the selected tower sample as compared to the reference sample. The AMPLITUDE mode displays the relative amplitude of the selected tower sample. The TEST mode is used to check the calibration of the instrument. Separate LED indicators display the selected mode.

The next two pushbuttons are labeled DOWN and UP. These buttons are used to select the tower to be monitored and displayed on the front panel LED displays. The selected tower number is shown to the right of these pushbuttons.

Two separate four digit displays are used to indicate the amplitude or ratio and the phase of the selected tower. The pushbutton to the right of the digital display is used to select the PATTERN. Separate LEDs indicate Day, Night, or a Third pattern. LEDs in the display also indicate if the monitor is under local or external control.

Performance Features

The 1900 Series offers improved performance and simplified operation at a lower cost than the current generation of AM-19 monitors. The 1900 Series indicates sample ratio directly with virtually no modulation effect: independent of the power level. The 1900 Series also provides the same phase accuracy, with automatic polarity indication, as the industry standard AM-19.

The 1900 Series utilizes a separate control/measurement module for each tower. The modules plug into the rear of the 1901 and 1903 units. This feature provides a continuous readout of the ratio and phase of each tower, simplifying the interface to a remote control device and eliminating input switching within the monitor. The modular design also simplifies expansion when another tower is added and eliminates extended downtime if a spare module is available on site. The 1900 Series can accommodate up to 12 towers.

System Interfacing

The 1901 and 1903 units provide a direct interface to a remote control device. Each of the control/measurement modules (one for each tower in the system) provides continuous analog outputs relative to the ratio and phase for each tower. These outputs may be connected to the telemetering inputs of the remote control device. The outputs may also be connected to an array of meters to prove a continuous and simultaneous display of each tower in the system.

External control inputs to the 1901 and 1903 units, in the form of contact closure to ground, can switch the units to the correct pattern and can also select the amplitude and test modes.

Modular Construction

The modular construction technique used in the 1900 Series simplifies expansion and repair procedures. All active circuitry is contained in modules that plug into the rear of the chassis. The unit does not have to be removed from the rack when adding or replacing modules.


Key Features:

  • FCC authorization number: IJ3PI1900
  • Digital display of ratio and phase of up to 12 towers
  • Same phase accuracy as the industry standard AM-19
  • Modular design simplifies expansion, reduces downtime
  • Provides continuous analog outputs of all tower measurements
  • Fully compatible with any standard remote control system
  • Simplified operating controls, local or external
  • Measurements for up to 12 towers in 5 1/4 inch rack height

Technical Specification

Technical Specification

Model 1901 alone or Models 1902 and 1903 together

Frequency Range: 540 kHz to 1700 kHz

Number of Towers 2 to 12

RF Inputs

Level range, reference: 1.5 V to 25 V RMS carrier

Level range, non-reference: 0.3 V to 25 B RMS carrier

Impedance: 50 Ohms, 72 Ohms, or Special

Connector UHF, adapters supplied to other types

Ratio/Amplitude Display

Ratio range: 0 to 1.999

Ratio accuracy: ±.010

Amplitude range: 0 to 1999, scale factor and decimal position user set

Patterns Up to 3 different reference towers; any number of power levels, subject to the input range limits.

Remote Data Outputs DC voltage proportional to parameter, separate outputs for each tower;

Ratio/Amplitude: 0 to 2.5 V for 0-1999 local display reading, for any decimal position

Phase: 0 to ±2.25 V corresponding to the range of 0 to ±180.0 degrees

1000 ohms ±1ohm

Connector: Plug for each tower with screw clamp terminals

External Control Inputs For external pattern and mode selection. Contact closure or collector to ground, +5 V open circuit. 10 mA closed circuit.

Dimensions 1901 and 1903: 19″ rack panel, 5 1/4″ high, 14″ deep

1902: 19″ rack panel, 1 3/4″ high, 6″ deep

AC Power 117 VAC ±10% or 234 VAC ±10%, 50-60 Hz, 50 VA maximum

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