Locus Radio Analyzer

[johnmoe1]

I was browsing the ARMER related minutes and read:
"Southeast (Freshwater)
The region is looking for grant funds to purchase a Locus Radio Analyzer, a scanner that scans for tuning radios that are out of tune. "
https://dps.mn.gov/entity/srb/committees/Documents/otc-minutes-november-twenty-fourteen.pdf

Seems to be this:
http://locususa.com/uploads/DiagnostX whitepaper1.pdf

If this kind of thing is useful, it seems strange that it isn't just built in. I would think that the towers are already measuring things like frequency error to be able to demodulate the signal.

 

[kb0uxv]

It listens to the control channel and logs what radios are out of alignment / drifted off frequency. The user sets how many hertz off the control channel is in "error" ; after around 5 PTTs the machine establishes a spreadsheet showing what radios are out of alignment. It saves time, currently every year or two a tech has to use a service monitor to individually tune every radio, since it is not known what ones are out of alignment, and only a small percentage of the fleet actually needs the service.

If the radio is too far out of alignment the user complains of digitized audio. If not corrected, the radio goes "out of range" even when in close proximity to a site. So this is a major user safety issue.

Unfortunately we recently learned the device falls under a "maintenance device" and is therefore not grant eligible. Some counties have purchased one of these on their own.

The Motorola Astro system is not capable of analyzing this data. The Locus device plugs into one of the output tower top amp ports on the site's receive antenna and can analyze any radio within the range of that site. In a multi site county the machine would need to be moved around to the various sites to capture the entire fleet.

 

[johnmoe1]

"The Motorola Astro system is not capable of analyzing this data" ... That is what seems sad to me. The system has to be measuring things like frequency errors to be able to successfully demodulate the incoming signal*. It also knows the radio id it is talking to. How hard would it be to combine these and put them in a text file that could be analyzed by hand or automatically with a few dozen lines of code?

* I suppose it is possible that this is being done in such a way that the part of the system that demodulates messages and the part of the system that decodes the messages are separate and don't communicate any meta data like frequency error.

 

[kb0uxv]

In the simplest sense, a modern P25 trunked site is just several repeaters grouped together, with a computer directing radio traffic to any available repeater. In ARMER, this is typically GTR8000 with the exception of the early sites which are STR3000 and in a very few cases Quantar. I am not aware of any repeaters on the market than detect or measure frequency deviation. But if a manufacturer designed this feature into a base radio I could see it as a huge benefit - every site could analyze traffic and it would save a tremendous amount of time and labor.

 

[NVAGVUP]

Additionally to kb0uxv's points, trunked repeaters demodulate user radio content, they do not decode it. (In the wide area trunked mode). Even in site trunking, the local site controller does the decode processing not the repeater.

Repeater receivers, whether they are trunked or conventional, are in place to demodulate a specific RF carrier frequency. The quality of the demodulated intelligence can be affected by many things. Freq error, low signal strength, deviation out of spec/tolerance, etc.

Although not as comprehensive as a technician level RF systems Analyzer, a Locus analyzer is a non invasive way of collecting user radio data. When an agency calculates the cost/benefit of having a report to flag "bad" radios and addressing them individually, vs taking every radio out of service to test (And the leg work to collect radios or run cars into the service shop) a Locus Analyzer starts looking more appealing. The cost to have a shop PM a good radio is the same charge as PM'ing a bad radio. How many good radios are checked and charges incurred during annual user PM's? Also take into account, the Locus report id's all bad radios into site, not just your agency. You other system/site users appreciate this kind of info also.