BDA Article

MTS2000DES

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Around here the problem is that AHJs have loose authority over BDA/DAS installations. I and other systems are dealing with a rogue BDA that is causing a loopback type of interference, it's clearly going into oscillation and presenting on the uplink of some (but not all) of our voice channels resulting in voice frames being repeated in a "max headroom" loop. We can see it on our spe-an clearly at around -110dbM at one subsite, but not others. We've got a general direction from the air from rooftops but on the ground, crickets.

I've spent hundreds of hours checking all "known suspects" by powering them down and rinse, repeat. I say all this to point out that there are many shadetree low voltage alarm contractors who see dollar signs and don't know shit about the black art that GOOD BDA/DAS design and implementation requires. They shuck a few hundred feet of LMR400, throw up some antennas, buy a box from Grainger or whoever, light it up and walk away. They'll leave the mess for the GC or building owner to clean up when they're long gone.

BDA/DAS should be a necessity only when absolutely necessary. I realize that this isn't popular with groups like the Safer Building Coalition, but there is a side to this that those who aren't RF people don't understand. We are collectively raising the noise floor to the point where no one is going to be able to talk and everyone will be shouting.
 

Bill_G

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We've had our share of glovebox BDA installers toss in systems without regard for isolation or gain adjustments. They fire it up and walk away. Within hours there will be three or four comm trucks converging on the property with yagis all aimed at the same rooftop, and we're all at the reception desk together asking who is in charge of their radios. Eventually some red faced IT guys and/or FAC guys are explaining how this group out of Salt Lake just finished, now their gone, and please don't turn it off ... as we pull the plug and watch the crystal city on our spec an's flatten out.

Depending on how nice they are, I'll help get the levels correct so they can keep their new toy. If they get redneck, I call the Fed Marshall, and let them explain why it has to stay off.
 

MTS2000DES

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The best experience I had was visiting Chick-Fil-A HQ. They just installed an ADRF unit in a parking garage. It was NOT the culprit and the work was done by an MSS. Well done at that. We (a tech from our MSS) showed up cold calling. They welcomed us with open arms. There is a reason why "Jesus Chicken" sells the way it does. During our many "spot checks" on known installs, we never had any resistance or issues, but we always try to call ahead and get someone like the building maintenance or security folks aware and prepared.
 

Keith

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I debated posting anything on this. Mostly due to folks knowing me locally and how it may be perceived.
Ohio, where I do business, has a state wide 700/800 radio system as many folks know.
The system owner, and a number of the big city users got together and have now set a requirement of needing the design, expected signal level from the donor to the closest site of the system, and a number of other technical aspects of the DAS systems. This of course adds an additional layer to the mix as we had national fire code, then the State added the OFC version of 510. The city I typically work in added a requirement for ALL cabling to be in conduit and be plenium rated to boot and now we need to submit all designs to the system owner that we are connecting the DAS equipment to in order to get their approval and they have been given the ability to DENY the installation of a system.

Personally I see it a couple of ways. We still have some JHA's that think a " can you hear me now " test is acceptable and if their radios "work" it's acceptable. But I also have inspectors that are not above condemning a building over them not having a working DAS. I hope that will all be rectified by this move and we will have consistency.
I did have one inspector that wanted stuff tested for fire, police, the local prison and the dog catcher in the only hospital in the county where they were. The costs to test this all was going to be stupid expensive and part of it was simplex frequencies. When I questioned it, the inspector got lippy to the point I explained that his only recourse was to condemn the building. But he may want to discuss that with his chief and the mayor and city council before doing so. As it may or may not impact his fire career and that of his chiefs. We ended up testing the coverage of the state wide system and the local VHF fire repeater and not for every fire dept that was in and out of the hospital or any of the law enforcement stuff. They did end up needing a DAS. But it was more than we wanted to take on. Not sure if they have a DAS at this point. But they are several counties away, so my guess is they found a trunk slammer and got a system from them.

Trunk slammer is the term I use in place of Bill's glovebox installer but it's the same thing. Guys that are trying to cash in on doing work they really aren't qualified to do.
We get a TON of that too. We actually had a school that first had a UHF DAS installed wrong that shut down out Connect Plus system (had a -50 dBm spike on the input of the control channel) and then when they got their public safety DAS installed for 800 they killed one of the simulcast sites for the county radio system as well. All from the same building.