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Application requirement: Remote repeater

General description:

An agency requires a repeater for low user density remote subscriber communication.

Communication modes:

Voice communications between field personnel.

Network configuration:

Standalone repeaters located in geographically dominant positions, such as mountaintops.

Power:

110/240 AC or 12 VDC from a battery bank.


Solution

Installation:

Subscriber unit operation:

Subscribers select the required talkgroup and communicate via the repeater. Digital subscribers will receive a busy signal if the repeater is processing another call from a different talkgroup.

A single or dual radio basestation is installed in a basic shelter as rack mount or as a floor mount cabinet. Direct antenna connections are made through the Rx and Tx connectors on the rear of the basestation, and AC or DC power is connected via the power connectors to the rear of the unit.

Basestation configuration

The basestation is configured with:

  • VHF or UHF transceiver modules;
  • VHF or UHF power amplifiers;

Interconnection:

None.

Talkgroup configuration:

All talkgroups are set up on subscriber units only, with groups either operating in Project 25 digital mode or analog mode with CTCSS, depending on the user terminals available within each group.

Basestation programming:

Each radio is programmed to operate as either:

  • A fixed channel with defined Tx and Rx frequencies, Rx and Tx network access codes, modulation scheme (digital or analog) and output power.
    The repeater will repeat any signal received on the selected channelís Rx frequency with the selected modulation scheme provided the signal has the correct NAC (in digital mode) or a valid CTCSS / CDCSS signal (in analog mode). Fixed channel operation is suitable if all subscriber talkgroups are on the same frequency pair.
  • Channel scan with each channel normally on a different frequency pair.

Variations

Telephone interconnect:

If field personnel have a requirement to make telephone calls then an interface module is required with 2-wire or 4-wire + E&M wireline interfaces. The repeater is connected via 2-wire or 4-wire landline or microwave link to the PSTN network.

Remote configuration / diagnostics:

Remote configuration and diagnostics are performed through a front panel RS232 port, using a modem and landline, or microwave. Alternately the ethernet port may be connected to an IP-based intranet.

Crossband:

If field personnel in different frequency bands need to communicate, two radios must be used in the repeater. The repeater is configured with UHF and VHF radios, and crossbanding software is activated. Crossband talkgroups are programmed into the basestation radios by entry of the corresponding crossband channel in each channel table.

The repeater then checks the Talkgroup ID or CTCSS code of all incoming calls and repeats on both radios for all talkgroups configured as crossband.

Link radio:

If communication to another nearby system or dispatch center is needed, two radios are required in a crossbanding configuration. One radio provides the repeat channel while the second radio is configured with a low power RF link amplifier, with all signals repeated over the link.

Dispatch calls may be sent over the link and repeated over the repeat channel.

Future Developments

Hot standby

If high reliability single channel operation is required in inaccessible locations (e.g. high mountaintops in winter), a second radio may be used as hot standby. The second radio, power amplifier and power supply are automatically switched in if the first radio / power amplifier / power supply fails.

Remote Configuration / Diagnostics

Remote configuration and diagnostics can be performed over an encrypted radio channel.