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Old 12-12-2017, 9:36 AM
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Default adding a 900mhz repeater to our fire station roof

Hello friends-

A 3rd party company is interested in adding a 900mhz repeater to the roof of our fire station. This will be used for remote meter reading. We currently use a 800mhz radio system as well as a UHF system for dispatching. Is there a possibility that this can cause interference with out public safety radios? Do they need to a be a specific distance apart? We have just recently found out about this project so i am trying to do a little bit of research. I have also asked for some sort of documentation stating it would not interfere but im not sure if i will get that.

Any help is greatly appreciated and if this is in the wrong section please let me know so i can move it to the correct place.

Thanks
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Old 12-12-2017, 12:45 PM
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I've got a few similar situations at a few of my radio sites. Most of it's cellular carriers coming in, but same stuff applies…

There should be some sort of contract to lease the site. That should including how much they are paying (if it's a commercial entity), how long the lease is for, renewal/termination terms, etc. Stuff that should be handled by your city/county attorney/legal department.
If this is a commercial utility or similar, make sure there is a contract for the site. Don't let them put something out there without rules.

Those rules should include (but not limited to) the following:
Specific verbage about what they are installing. Including specs on the radio, antenna, etc.
Specifics about electrical connections, if any.
Specifics about how the equipment is installed, up to code, inspected, etc.
Specifics about what happens if/when the lease is terminated, including removing -all- equipment and restoring the site to original condition ( should include holes plugged, all gear removed, clean up, etc)

There should absolutely be a section about how in the event of interference, there is a set time to fix the issue, like 24 hours or less. If it's not fixed, the equipment gets shut down. Use specific wording about life safety radio systems and the importance of no interference. That way if there is an issue, you've got some control over the situation. If you don't do this, it can turn into a bunch of finger pointing and that's a big issue.

If everything is installed correctly using proper cable, connectors, radios, etc. - AND - there is appropriate separation between the antennas, there shouldn't be an issue. Usually these meter reader radios are low power, so that reduces the chances. Likely they'll be more concerned about interference from your stuff, as your radios will be running higher power.

There's a lot of things that can cause interference, so it's hard to give you a 100% answer, but if you make sure there are words in the lease agreement/contract that address interference mitigation, you should be OK.

Considering there are a lot of these systems all across the country, I think you are pretty safe.
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Old 12-12-2017, 12:49 PM
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Thank you for the reply!
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Old 12-12-2017, 12:56 PM
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With the FCC's Rules transitioning to the measurement of power flux density for cellular systems, it appears that actual RF hitting the street will be significantly higher. There is already concern for 700 and 800 MHz public safety users. The FCC held a session on this recently and organizations like NPSTC are following the situation very closely.

The meter systems I'm familiar with are 902 - 928 SCADA, which are usually much lower power, but might be situationally problematic. Regardless of the frequency and power levels, mmckenna brings up many valid concerns. Make certain your roof or tower rights are clear and well-defined. Likewise for roles and responsibilities.

You might want to invest in a communications or commercial property attorney who is familiar with the services to make sure your future interests are represented and there can be no "gotchas" later on.
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Old 01-27-2018, 10:20 AM
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Quote:
Originally Posted by JRSpero View Post
Hello friends-

A 3rd party company is interested in adding a 900mhz repeater to the roof of our fire station. This will be used for remote meter reading. We currently use a 800mhz radio system as well as a UHF system for dispatching. Is there a possibility that this can cause interference with out public safety radios? Do they need to a be a specific distance apart? We have just recently found out about this project so i am trying to do a little bit of research. I have also asked for some sort of documentation stating it would not interfere but im not sure if i will get that.

Any help is greatly appreciated and if this is in the wrong section please let me know so i can move it to the correct place.

Thanks
The Itron Smart Meters utilize the 902-924 Spread Spectrum ISM band for low power telemetry use.
We measured one at 915 Mhz with an output of -3.3dBm so around .468mW. They are in a mesh network, and
their signal is received via an antenna mounted up on a street lamp or other suitable structure.

The interesting part for us is there has not been enough time or data collected to understand the long term effects of exposure to non-ionizing radiation, near humans with these devices installed pulsing RF 24/7/365.
We see a lot of these devices on the outside wall adjoining a bedroom, as this is where the power panel to a residents was installed.

Look up the FCC identifier: SK9C1A-2
Not sure what State your in, they may used a different meter, however, they are all subject to Part 15 Spread Spectrum Devices.
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Old 01-27-2018, 11:17 AM
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The interesting part for us is there has not been enough time or data collected to understand the long term effects of exposure to non-ionizing radiation, near humans with these devices installed pulsing RF 24/7/365.
Actually there have been plenty of studies looking at the health effects of exposure to RF at pretty much every frequency, from DC to daylight. There is no unique danger associated with milliwatt-level 900MHz exposure.
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Old 01-27-2018, 11:47 AM
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The interesting part for us is there has not been enough time or data collected to understand the long term effects of exposure to non-ionizing radiation, near humans with these devices installed pulsing RF 24/7/365.
I agree with Jon, this has been well studied.
The key to remember is "pulsed". Actual transmitter "on" times are extremely short.

While different frequencies, consider marine radars running power levels in the hundreds to kilowatt range in close proximity to boat operators, crew, passengers. Pulsed RF is the important part to remember.

Also, remember the power/distance calculations. While the transmitter might be running 1/2 a watt, that power falls off rapidly.


I pulled one of the "Smart Meter" fear posters that were being put up around our town a few years back. I have it framed in my office as a reminder of the general lack of understanding the public has regarding radio. The widespread confusion regarding ionizing versus non-ionizing radiation is the other reason I keep it. It generates more than a few conversations with visitors.
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