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Old 04-09-2014, 6:50 PM
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Question Broomfield Flatirons Mall & mystery DTRS site

So, today while visiting the flatirons mall I encountered strong evidence of an "unknown" DTR site (i.e. not listed in RR), which seems to provide excellent in-building DTR coverage to DTR radios. As far as I know, broomfield PD officers assigned to the mall only carry a single DTRS radio, and the mall UHF security channel is not patched to DTRS. Any idea what might be going on here??
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Old 04-09-2014, 11:33 PM
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So, a bit of research reveals that Broomfield has a G-Wave Bidirectional amplifier in the Flatirons mall, presumably to somehow extend radio coverage. How would such a device extend DTRS coverage? Would such a device use unique frequencies in the 700/800 band (as opposed to duplicating freqs from a DTR site)?

I believe Broomfield PD uses XTS 5000s and XTS 3000s, presumably in the 700/800 band, no UHF or VHF. AFAIK not a single agency in Broomfield owns, let alone uses, conventional radio systems other than the Jail's UHF system. So, it seems like the Bidirectional Amplifier referenced above would operate in 700/800...?
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Old 04-10-2014, 12:44 AM
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This is installed in most large buildings. This is most likely required by the fire department, after the drywall is installed we will survey the building if needed a large cable used as a antenna is installed throughout the building ceiling and a amplifier is installed and a antenna is pointed at the best tower to boost the signal. It just boost a signal from a portable radio in what is normally a "dead spot" so you will not "go digital "
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Old 04-10-2014, 8:21 AM
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Quote:
Originally Posted by 04Z1V6 View Post
This is installed in most large buildings. This is most likely required by the fire department, after the drywall is installed we will survey the building if needed a large cable used as a antenna is installed throughout the building ceiling and a amplifier is installed and a antenna is pointed at the best tower to boost the signal. It just boost a signal from a portable radio in what is normally a "dead spot" so you will not "go digital "
How would such an antenna work with a Trunked site/system such as DTRS?
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Old 04-10-2014, 3:38 PM
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After a bit of field work, it appears they are probably "amplifying" the squaw mountain DTR site. However, there were certain areas of the mall that had no coverage from any P-25 system in 700/800 band; this includes virtually the entire food court area, which you would think they would want to cover with an in-building amplifier. Perhaps in certain areas they only amplified the "repeater input" signal. In any event, I've NEVER heard anyone complain about radio signals inside the mall, so I'm still thinking I could be missing something.

Maybe they're doing something funky outside of DTRS, such as tying the in-building antenna site to a conventional 700/800 channel pair and back-hauling the "other side" to the dispatch center with a cable or microwave link, instead of an exterior antenna. That would take a bit longer to find, because I would need to search for a intermittently active conventional channel, as opposed to a P-25 CC which is always active and is easily identified with my 396XT's "DAT" flag.
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Old 04-10-2014, 5:32 PM
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I don't know much about this subject so the following should not be considered factual answers.

My impression of the technology is that the amplifiers basically act a wideband signal repeater, therefore amplifying most of the 700/800MHz band. They are most likely very comparable to the "signal extender" found in the WiFi and cellular markets. From reading about it, it sounds like it simply takes the signal received on an external antenna and increases the power of the signal and then re-radiates the signal within the building, therefore acting as if the end user was outside and line of site with one of the towers. Being bidirectional would mean that public safety radios would be able to transmit within the building which is then picked up by the amplifier before being sent out on the external antenna. It doesn't sound like it does much more than that.

As for signal issues and looking up the floor plans for the mall, it is possible that you're experiencing multipath distortion issues as you can also think of these amplifiers as a "simulcast" of the site it is receiving as it takes time for the amplifier receive and re-radiate the signal. If this is the case, then many scanners would have a difficult time receiving a signal while a much more superior portable radio would be able to decode just fine. It's also possible that the amplifier is amplifying cellular signals as well, which could be intentional or unintentional depending on how they design their system. This may washout your ability to receive DTRS, which once again is likely handled much better on actual public safety radios.
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