VHF Bi-Directional Amplifier

[70cutlass442]

A local school has asked our department what we recommend to improve radio coms inside a school. They are preparing for a referendum and which will include various safety upgrades.

We use VHF P25 (conventional) but I have heard that BDAs in high-band are very difficult to tune and use effectively. Can anyone share their experiences with such equipment?

Is there a VHF/700/800 BDA? (fire is on 800 trunked).

My simple solution for this would be install a repeater inside the building and link it to our existing infastructure. We accomplished just that for around $5k at the local hospital and simply installed the repeater in a telco closet. The hospital then provided a fiber WAN connection that we tunneled over. The portables then vote scan when in the hospital.

If a BDA that covers both bands can work, I would be inclined to purpose that.

 

[mmckenna]

A local school has asked our department what we recommend to improve radio coms inside a school. They are preparing for a referendum and which will include various safety upgrades.

We use VHF P25 (conventional) but I have heard that BDAs in high-band are very difficult to tune and use effectively. Can anyone share their experiences with such equipment?

VHF tends to have a high noise floor, which can be problematic.
Also, BDA's in general are know noise makers and if not set up/maintained correctly, they will full on destroy your VHF system completely.

Huge issue is that these things get installed by people that have zero idea how to properly adjust them. They take the money and walk away. Your agency will get stuck with the fallout from that (it WILL happen).
Other issue is that these systems get turned on and forgotten about. They require periodic testing by someone who understands how they are supposed to work (not a fire fighter with a radio doing radio checks), and periodic adjustment.

I'll pause here for @MTS2000des to share his extreme frustrations with these systems…..

Is there a VHF/700/800 BDA? (fire is on 800 trunked).

I've always seen them installed as multiple systems, one for each band. Coverage/needs will be different, so usually a 'one size fits all' thing does not work when playing on different bands.

My simple solution for this would be install a repeater inside the building and link it to our existing infastructure. We accomplished just that for around $5k at the local hospital and simply installed the repeater in a telco closet. The hospital then provided a fiber WAN connection that we tunneled over. The portables then vote scan when in the hospital.

That is a much better solution than BDA's.
There are fiber fed Distributed Antenna Systems, if this is a large school, that can work better.
Whatever you do, don't let someone buy Chinese $**t off Amazon and install it. These systems need Part 90 certified equipment and they absolutely have to have permission from the licensee to be installed.

If a BDA that covers both bands can work, I would be inclined to purpose that.

I'd avoid BDA's at all costs, especially if the school is paying. They'll jump at low bid. They'll also cut the budget next year and that system will never get maintained.


It would be absolutely worth every single cent to hire a professional designer (not a contractor calling themselves a designer) to properly study the needs and design a system. Then have that system installed.

Some agencies are now setting these things up so they get installed and turned off. They only get turned up when needed by dispatchers, or fire fighters arriving on scene.

 

[mmckenna]

Not sure what kind of radios you have, but there are some agencies that are starting to embrace Motorola Smart Connect or Harris BeON to solve these issues. LTE coverage is usually pretty good in buildings, and they can utilize WiFi.

You might want to start working with your agency to develop standards/guidelines beyond fire code regarding these systems. If the AHJ starts adopting this into their code, you guys are going to want some teeth to keep them under control. You don't want people just tossing these things into new construction without your agency knowing about them. That's bad ju-ju.

 

[70cutlass442]

Not sure what kind of radios you have, but there are some agencies that are starting to embrace Motorola Smart Connect or Harris BeON to solve these issues. LTE coverage is usually pretty good in buildings, and they can utilize WiFi.

You might want to start working with your agency to develop standards/guidelines beyond fire code regarding these systems. If the AHJ starts adopting this into their code, you guys are going to want some teeth to keep them under control. You don't want people just tossing these things into new construction without your agency knowing about them. That's bad ju-ju.

I expected you to chime in and I appreciate the response. You have confirmed some of my fears. We are not opposed to an LTE solution and demoed several about two years ago before selecting the current P25 system. The issue that admin. had was any recurring cost associated with an LTE deployment. Don't ask me why....

I will probably work with the district to put repeaters at each school since they are a fraction of the cost of a DBA. We also want to work with their IT department as they have their own fiber network between all of the schools. They have a drop at a village owned location that we are currently running fiber to. I would think we could build an extremely low latency LAN to run all of these repeaters on that would connect back to our wide area repeaters on private fiber.

Thanks for the input!

 

[mmckenna]

I expected you to chime in and I appreciate the response. You have confirmed some of my fears. We are not opposed to an LTE solution and demoed several about two years ago before selecting the current P25 system. The issue that admin. had was any recurring cost associated with an LTE deployment. Don't ask me why....

Yeah, even with the very basic service you'd need through FirstNet/AT&T or Verizon, it starts to add up if you have a lot of radios.
One of the reasons why WiFi is a good option. Most schools have robust WiFi networks. Not a good solution if you were in there fighting a fire, but you'd probably be on a fire ground channel at that point anyway. I'd bet most of your calls there are medical anyway, and WiFi would work just fine.

I will probably work with the district to put repeaters at each school since they are a fraction of the cost of a DBA. We also want to work with their IT department as they have their own fiber network between all of the schools. They have a drop at a village owned location that we are currently running fiber to. I would think we could build an extremely low latency LAN to run all of these repeaters on that would connect back to our wide area repeaters on private fiber.

Man, that's what I'd do. Do some testing, though, you may find that your repeater reaches in the school just fine, it's getting the signals from the portables back out. A simple voting receiver might solve all your issues.

 

[mmckenna]

You are still probably going to get an earful about BDA's from @MTS2000des , and maybe a few others. Just be prepared to duck.

I went to a round table discussion on those systems that was attended by mostly fire department officers. They had some real horror stories about these systems. The tide is starting to turn on the NFPA, and the requirements that they get installed in so many places. Bird RF is rumored to be getting out of the BDA business since it's turned into such absolute C.F. and they don't want to be associated with it anymore.

Too many guys with their 3 day sessions GROL licenses that are installing these things with no understanding. I won't touch them and am actively trying to avoid getting sucked into it at work. I'm pushing for WiFi/LTE where appropriate, and if that won't do it, a fiber fed DAS system. We had NexTel BDA systems for a while, and those were constantly FUBAR'ing up our trunked system.

 

[MTS2000des]

I spent 6 months of my life without sleep because of some Richard Cranium installed BDA that had zero authorization to even be on my system. When it went on the air, it wreaked havoc on our 12 channel, 15 site 800MHz trunking system not just throwing hash and trash on 5 of our 12 channels causing them to be voted out of wide area service, (at 6 channels out, we would have been in failsoft system wide), but it also had this nasty oscillation that would cause voice packets to be repeated in the ear of consoles, a Max Headroom effect that drove users and dispatchers alike crazy.

Thousands of man hours and thousands of dollar later, an astute technician from our MSI service shop found this road apple redneck installation and as soon as the donor antenna disconnected, all was quiet again. Look at this piece of Baofeng (another word for TURD) that was the source.

If you need in building coverage, a BDA is a fine way to drop hundreds of thousands and if not done well, you may wind up hindering, rather than helping your cause, and in the long run, it may be more feasible to look at LTE/broadband integrated subscribers if a system supports it.
While the cost will be there subscription wise, the peace of mind knowing you aren't having to invest tens to hundreds of thousands for some venerable BDA that may actually cause harm to your wide area system may pay off. BDAs also need monitoring, maintenance and yearly testing too- they aren't "set and forget" systems by far.

 

[WB5UOM]

But. but. but..
it is in an official RED housing...should be ok

 

[WB5UOM]

I think I am in the midst of one of these 800/vhf that someone did on a new building, looks cleaner than tjat one, but when talking to the folk, its like " oh its good, if theres a problem, its with your equipment"

 

[xmo]

Every public safety system administrator needs to get up to speed on the BDA (technically ERRCS) issue because it's only going to get worse.

You need to harmonize with local fire officials and develop comprehensive policies. The policies need to be formalized with the admin of the city or county that holds the license. Then, if an unauthorized system is discovered, you don't have to jump through any FCC hoops, you just show up with code enforcement, have a citation issued, and pull the plug on it.

The challenge is the effort and time it takes to attain proficiency in this area and then to develop technically and legally supportable policies. A lot of the communications department policies you can find on-line are based on fire code and don't address protection of your system.

Here is a sample retransmission consent form:

 

[Project25_MASTR]

Oh BDA's.

So much fun dealing with OBT trunking and VHF BDA's...

 

[TampaTyron]

Just found one of these VHF BDAs...... was killing 3 channels of a local 4 channel VHF 6 site simulcast system. Previous shop had about 250 hours billed in finding the source of the noise. Found it in four hours. It was a misconfigured BDA that the same shop installed. About 1/2 mile from the tower site and the only thing within 10 miles of the tower. The swore it wasn't offending and refused to turn it off. Had the local Sheriff order me to pull the plug.

I get accused on occasion of having equipment that is offending. I am not perfect, but am the first one to shut it off so as to not waste anyone's time. Our industry is rapidly changing and not for the better. We are rapidly growing, not because new customers/systems, but because the competent parts of the industry are shrinking. TT

 

[MTS2000des]

Our industry is rapidly changing and not for the better. We are rapidly growing, not because new customers/systems, but because the competent parts of the industry are shrinking. TT

It's like having fry cooks or clowns assembling airplanes. The consequences aren't just an inconvenience.
BDAs, DAS, duplex communication systems using LMR RF require advanced skills and experience, as well as expensive test equipment, to do right. The BDA/DAS industry has been overtaken by "Chuck and a Truck" low voltage contractors the same way Bowelturd radio and "test question memorizers" have invaded part 97. Neither has any business meddling with RF FNE.

 

[TampaTyron]

I see a lot of parallels between our industry and like that of the Boeing/Spirit Aviation ongoing issues........ public safety and old guys falling off (or were pushed out), new non-technical managers tell the remaining survivors that they will "produce numbers or else". Then, cry foul when quality drops like a rock. Getting rid of anyone who try to show anyone a "better" way. TT

 

[speedway_navigator]

Does the school need to talk outside the campus? A DMR system with repeaters using the vote/scan function (know as site connect or IP connect depending on the mfg's trademark) might work.