Maximum performance of trunking system via modulation level tuneup.

There are several simple preventative measures SMR/CMRS operators can take to keep trunked radio systems (and revenues) at peak performance. Our current rate for expert radio repeater system checkout is $4200 (one day) for a 5 channel LTR trunked system plus travel charges in the Midwest. This tuneup is recommended on a yearly schedule, although if you have your own staff and equipment once every two or three years is also a common option. This rate includes on-the-job training for up to two staff members while we tune the system, space permitting in the room. Circuit repairs are not included in this rate, nor are parts or antenna system components. Tower climbs if necessary are contracted through a local provider. Networked systems are at additional charge, as well as voting systems. I also evaluate microwave links and leased lines and can assist in upgrading your system for analog or digital backbone. Pricing is proportional to effort level, using $4200/day as a baseline.

For safety, we do not exceed nine-hour workdays, plus one-hour round-trip site travel time. Sites with exceptional access needs (helicopter, rope climbing) may exceed what we can provide and we can instead provide training at your office on your spare hardware. We can also setup monitoring in a vehicle with cellular connection to your staff acting as the hands on controls in these situations, which are relatively rare in the Midwest vs. West.

Basics of trunked system level optimization vs. range

  • Motorola Type I/II trunking uses a 3600 baud (2 level FSK) with +/- 3 kHz deviation
  • LTR, MultiNet II and similar systems use approximately 300 baud data with +/- 1 kHz deviation on 25 kHz systems and +/- 800 Hz deviation on 12.5 kHz systems.

These general classes of systems (BFSK) whether high or low speed are quite sensitive to deviation (how much modulation) of the control channel data. Eb/N0 is SNR scaled to a bit, so neglecting excess bandwidth of the real receiver. Whether SNR or Eb/N0, halving the deviation is a 6dB energy penalty, so a 0.1% BER becomes a 6% BER for a theoretical binary FSK receiver with coherent detection. At what point your control channel decode breaks down is also influenced by ever-present fading on the channel.

To get an exact idea of what BER your system tolerates is a matter of measurement, as OEMs don’t publish these specs. Sometimes brand name radios perform much worse than the generics! Different firmware versions, hardware revisions, etc. all come into play. Of course the static tests tell you something about -119 to -122 dBm is about the best you will get and you can work back an approximate minimum BER from that. By allowing a “hang time” where no correct packet is decoded yet the squelch stays open is how systems enhance their fringe range in typical mobile fluttering signal conditions.

An ill-tuned modulation is quite easily like a malfunctioning power amplifier, but easier to detect remotely. We can provide you with a remote monitoring solution for your trunked system that remotely monitors

  • power amplifier failure (via local RF sniffer)
  • antenna failure (via radio receiver at your office)
  • modulation level (via radar receiver at your office)
  • tower top amplifier failure (via local RF injection)

It only makes sense to monitor all channels, which we do at the combiner output and we monitor the individual transmitter lines to see which channel may be failing. The remote sensing option is less expensive, provided your office is within range of the tower site you wish to monitor.

Our controller monitors the RSSI of a radio programmed for your system. If the radio does not have channel steering, we use channel button pulsing and a channel programmed to a “birdie” of the radio to act as a reference in case power is lost to recover what channel the radio is on. We work on a time and material basis, $300/hour to develop a system for your needs, with $5000 minimum charge.