RadioReference on Facebook   RadioReference on Twitter   RadioReference Blog
 

Go Back   The RadioReference.com Forums > Commercial, Professional Radio and Personal Radio > Industry Discussion


Industry Discussion - General discussion forum for commercial and professional radio technologies. This includes manufacturers not listed below.

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
  #1 (permalink)  
Old 04-13-2018, 7:55 PM
Member
   
Join Date: Mar 2010
Posts: 914
Default BDA's and potential interference

I am interested in starting a discussion about bi-directional amplifiers and interference (not related to bad installation practices).

BDA's are becoming common, and a big push with the NFPA. On lower frequency systems, 150-512 Mhz, wideband noise (RFI) is becoming a common issue with land mobile radio. This issue is caused by newer electronics, LED lights, switching power supplies and so on and so fourth. It is to the point that degradation in these bands is a major issue in handheld and mobile radios operating in new vehicles because of "noise".

I have been aware of some situations in the VHF band with use of BDA's that are amplifying this wideband RFI out of the building and to the system receivers creating a very high noise floor and severely degraded performance of the system. A proper installation of the system may be OK at the time of installation, but may change with the addition of "whatever" in the building that cause severe garbage that is becoming the norm. Of course, the more BDA's with this, the more the problem. A little bit of noise (and RF power) into a high gain antenna pointed at the system receiver(s) is of concern.
Reply With Quote
Sponsored links
  #2 (permalink)  
Old 04-13-2018, 8:32 PM
Member
  Premium Subscriber
Premium Subscriber
 
Join Date: Jan 2006
Location: Harrisburg, PA
Posts: 150
Default

This problem can be significantly reduced by installing Class A (channelized) BDAs. My company uses Class A BDAs as much as possible to limit the potential interference to the system.
Reply With Quote
  #3 (permalink)  
Old 04-13-2018, 8:42 PM
MTS2000des's Avatar
Member
  Amateur Radio Operator
Amateur Radio
 
Join Date: Jul 2008
Location: Cobb County, GA Stadium Crime Zone
Posts: 3,284
Default

It's not just a matter of running class A, it's also doing a solid spectrum study of the site over days/weeks to evaluate the noise floor. While channelization may prevent some garbage from getting through, I found out that in our implementation (800MHz) we had to install a custom notch filter to block out LTE on adjacent channels. It was just too noisy in a downtown area. All kinds of crap got sucked into the BDA and caused frame slip issues, high BER, and garbage on the downlink.

BDA's are a black art that require expertise. Sadly, too many "eggspert teknishuns" from skilled plumbers to electricians are now selling and installing these, and more often than not, the offshore garbage with dubious specs and performance when setup by an expert let alone a novice who got their "experience" watching YouTube videos and is now an RF in building coverage expert.
__________________
NO I will not help program your trunking radio. All opinions are exclusively those of the author and in no way reflect the position of his employer, contractors or other parties.
Reply With Quote
  #4 (permalink)  
Old 04-13-2018, 8:51 PM
Member
   
Join Date: Mar 2010
Posts: 914
Default

Quote:
Originally Posted by MTS2000des View Post
It's not just a matter of running class A, it's also doing a solid spectrum study of the site over days/weeks to evaluate the noise floor. While channelization may prevent some garbage from getting through, I found out that in our implementation (800MHz) we had to install a custom notch filter to block out LTE on adjacent channels. It was just too noisy in a downtown area. All kinds of crap got sucked into the BDA and caused frame slip issues, high BER, and garbage on the downlink.

BDA's are a black art that require expertise. Sadly, too many "eggspert teknishuns" from skilled plumbers to electricians are now selling and installing these, and more often than not, the offshore garbage with dubious specs and performance when setup by an expert let alone a novice who got their "experience" watching YouTube videos and is now an RF in building coverage expert.
Good points. But, many of these systems are written into city codes. If it's "installed" then all is good as far as local officials are concerned.

BDA's can cause more harm than good. You're right, it is a art so to speak. My concerns are, who maintains these? You mention LTE, and special notch filters. What happens in 3 years when something else comes along, and there is 100 of them in a 5 square mile radius? What happens about generated garbage inside the building itself, that is added or altered, a big deal on lower frequencies. You think 800 is bad, try VHF!

The whole requirement for a building or occupancy permit thing leaves a bad taste in my mouth.. On paper they sound great, but real world applications they can be a disaster waiting to happen.

Last edited by 12dbsinad; 04-13-2018 at 9:50 PM..
Reply With Quote
  #5 (permalink)  
Old 04-14-2018, 8:09 AM
Member
  Premium Subscriber
Premium Subscriber
 
Join Date: Jul 2006
Posts: 105
Default

The thing with BDAs is that the indoor and outdoor antennas need to be separated enough that they can't hear each other. If the do, there will be feedback and the BDA is just going to radiate noise on or near it's intended frequency. Back in the nextel days, there were nextel BDAs all over the place. Businesses, homes, stores, warehouses. Over the years nextel shut down and the BDAs remained in place and turned on, abandoned. After a decade or so, the components of the BDA broke down and the BDA for whatever reason started feeding back and generating random carriers.

I maintain a trunk system for a living. The system will report an "illegal carrier" when there is an interfering signal on our input frequency. We fox hunt the interference and shut it down. 15 years ago, most of what we found was Nextel BDAs. Over time, we see less and less Nextel BDAs and more and more cheap chinese amplified TV antennas and other electronics that don't have a part 15 certification. Of course we do still find some fire department BDAs that either are turned on accidentally before installation is complete, or BDAs that feed back because the antenna falls over on the roof, or antenna was never waterproofed and the SWR went up over time.

Around here, BDAs are required by fire code and as such the permits and inspections are done by firefighters. In many cases they don't know the first thing about radios or RF, so they may check that the BDA has correct battery backup, but RF performance isn't even considered.

Last edited by mrsvensven; 04-14-2018 at 8:14 AM..
Reply With Quote
Sponsored links
  #6 (permalink)  
Old 04-14-2018, 8:24 AM
MTS2000des's Avatar
Member
  Amateur Radio Operator
Amateur Radio
 
Join Date: Jul 2008
Location: Cobb County, GA Stadium Crime Zone
Posts: 3,284
Default

Quote:
Originally Posted by 12dbsinad View Post
Good points. But, many of these systems are written into city codes. If it's "installed" then all is good as far as local officials are concerned.
At my agency, we send a member of the radio team to inspect and review the as builts, meet with the building contractor/owner, and advise them they have to have their BDA registered with the FCC, advise them it must be an FCC certified unit, and we require them to submit a test report showing it's functioning properly and in compliance. We use our spectrum analyzers and subscriber radio, visit the site and area once they "go live" and verify there is no interference.

It is on each system manager/agency staff to do this work. I know, not everyone has this, and it will most likely fall through the cracks until someone complains.

Quote:
Originally Posted by 12dbsinad View Post
BDA's can cause more harm than good. You're right, it is a art so to speak. My concerns are, who maintains these? You mention LTE, and special notch filters. What happens in 3 years when something else comes along, and there is 100 of them in a 5 square mile radius? What happens about generated garbage inside the building itself, that is added or altered, a big deal on lower frequencies. You think 800 is bad, try VHF!
VHF is useless in urban areas. We migrated off of VHF in the early 1990s. The noise floor around our downtown area is absurd. It would take 50-100 watt mobiles to overcome most of the trash. Forget using a portable, let alone body worn with an RSM. I feel for anyone who has to content with the noise generators that range from LED lighting, cheap cellphone chargers, CPU clocks, you name it, it's generating RF in the 150MHz range.

Quote:
Originally Posted by 12dbsinad View Post
The whole requirement for a building or occupancy permit thing leaves a bad taste in my mouth.. On paper they sound great, but real world applications they can be a disaster waiting to happen.
All of this falls on the shoulders of local jurisdictions and their capabilities. A large agency like where I work has a staff of 8 full time technical staff, one of us (me) is an ETA certified RFIM technician. I can see where many agencies don't have this and most likely pawn off the work to a local service shop, and they may or may not be consulted or assisting.

It's a problem that isn't going away. RF noise pollution is as detrimental to radio spectrum as dumping sewage into drinking water supply. Yet the FCC is too busy peddling spectrum to the telecom cartels and leaves the work to you, the end user/system manager, to figure out and deal with on your own.
__________________
NO I will not help program your trunking radio. All opinions are exclusively those of the author and in no way reflect the position of his employer, contractors or other parties.
Reply With Quote
  #7 (permalink)  
Old 04-14-2018, 8:28 AM
MTS2000des's Avatar
Member
  Amateur Radio Operator
Amateur Radio
 
Join Date: Jul 2008
Location: Cobb County, GA Stadium Crime Zone
Posts: 3,284
Default

Quote:
Originally Posted by mrsvensven View Post
Around here, BDAs are required by fire code and as such the permits and inspections are done by firefighters. In many cases they don't know the first thing about radios or RF, so they may check that the BDA has correct battery backup, but RF performance isn't even considered.
Your agency should be involved in the process. Ever approached the fire chief(s) and discussed this with them? What will get their attention quick is when you mention the key words "LODD" and "IDLH" with "non-compliant life safety equipment".

It's what we do. We have 6 different fire agencies on our Astro 25 7.14 (soon to be 7.16) M-core simulcast system. We require that any BDA being installed in our coverage area forward the name and contact of the contractor installing it, the system design, FCC registration information, and then follow up with a review and walk through.

You can't leave it to someone else to do it because as you said, they lack the skill set.
__________________
NO I will not help program your trunking radio. All opinions are exclusively those of the author and in no way reflect the position of his employer, contractors or other parties.
Reply With Quote
  #8 (permalink)  
Old 04-14-2018, 9:22 PM
Member
   
Join Date: Feb 2009
Posts: 508
Default

If you need to use BDAs, then you need to fix the REAL problem which is lousy repeater coverage.
...........
Most systems are poorly designed using the wrong tower locations
and the wrong atennas.
............
Yes BDAs are in fact causing as many problems as they cure
Reply With Quote
  #9 (permalink)  
Old 04-14-2018, 10:36 PM
mmckenna's Avatar
Member
   
Join Date: Jul 2005
Location: WTVLCA01DS0
Posts: 9,187
Default

Quote:
Originally Posted by MOTEX View Post
If you need to use BDAs, then you need to fix the REAL problem which is lousy repeater coverage.
In many cases, it actually has to do with newer building construction. You can have a strong signal outside, but step into a modern building, and it can drop pretty quick. Low-E glass, metallic vapor barriers, reinforced concrete, energy efficient systems, etc, etc…

I have a building at work. It's next door to a DAS cell site. I can stand in the building looking out the floor to ceiling windows at the cellular antennas 75 yards away, and get nothing on my cell phone.

Same happens with public safety systems. Rather than cranking up the power on the repeaters or using some ungodly amount of tower locations, it's easier, cheaper and makes more sense to require BDA systems.

Quote:
Originally Posted by MOTEX View Post
Most systems are poorly designed using the wrong tower locations
and the wrong atennas.
Very likely so, but there's a lot more to it than that. It's not just poorly designed systems. Systems that once worked great no longer do inside some newer buildings. Add a bunch of steel and it can cause system shadows. Lots of issues going on here.

Quote:
Originally Posted by MOTEX View Post
Yes BDAs are in fact causing as many problems as they cure
I'd say "Cite your sources", but that's probably pointless. Properly designed, installed and maintained systems should not be causing issues.
The problems are many:
-Systems that haven't been designed/engineered. Often some data networking contractor says "Hey, we can install that for you".

-Systems installed by people not knowing what they are doing. Nextel sent a contractor in to several of our buildings many years back to install BDA systems. We had one site that was causing interference with our 800MHz trunked system. When I went through tearing some of these BDA systems a few years ago, we found Heliax connectors that were not properly installed, basically held on the cable with electrical tape.

-Cheap BDA's from China. No FCC certs, but hey, they're inexpensive!

-AHJ's/inspectors not having a clue what they are doing.

-Systems not getting tested annually.

-Systems not maintained.

-Systems not being updated when modifications are made to the building.

- Fricken *^&%#@ roofers messing with the antennas.

- Fricken *#(&$#* IT guys thinking they know how to set them up.

The NFPA has some good rules on these systems, but I don't think they go far enough. The average fire fighter or fire marshal that gets sent out to check these things usually has no technical understanding of radio systems.

Truth is, there's a lot of money to be made in designing, installing, maintaining and testing these systems. local jurisdictions need to understand that making sure they are working correctly is important. Unfortunately building owners don't want to pay for it.
Reply With Quote
  #10 (permalink)  
Old 04-14-2018, 11:02 PM
Member
   
Join Date: Feb 2007
Location: 175 DME, HEC 358° Radial
Posts: 5,590
Default

Quote:
Originally Posted by MOTEX View Post
If you need to use BDAs, then you need to fix the REAL problem which is lousy repeater coverage.
Nope, I'm not buying that one.

In the course of reverse engineering one system's coverage problems, and develop the requirements for the replacement system, I once did a series of tests to determine typical losses in various types of buildings, as well as other operational circumstances such as operation with a portable on the hip with a speaker/mike.

Careful measurements were made in commercial and residential structures, concrete and steel high rises, to wood frame houses. Just to put things into perspective for you, I observed and measured tinted window glass that had 50 dB of loss at 800 MHz. That's ONE pane of glass with 50 dB of loss due to the metallic tinting.

Operating the radio while it's in a belt holster at hip level costs about 17 dB at 800 MHz. Just inside the first wall of a wood frame stucco house is about 10 to 15 dB.

Current operational requirements frequently now call for radio coverage inside commercial and residential buildings. It's "reasonable" to design system coverage sufficient to overcome the losses incurred by hip worn portables, inside a residential structure. but when you start throwing in 50 dB losses from insulated and reflective glass in steel and concrete buildings, a BDA is mandatory if inside coverage is required. And frequently it is.

Use of a BDA to augment coverage, especially if it's incorporated into new system design is considered good engineering practice, provided it's actually engineered, and not just thrown in.
Reply With Quote
  #11 (permalink)  
Old 04-15-2018, 3:09 PM
Member
   
Join Date: Mar 2010
Posts: 914
Default

Most of my state is VHF. Many urban areas are still VHF, these are small "city's" with a population of 30-70K people. Some of them are VHF P25 and most are still analog. These city's are approving BDA installation without understanding the ramifications, especially on VHF.

People don't understand that whatever garbage noise generators are in the building, gets amplified to the outside with high gain antennas pointed at the system receivers. Then they wonder why the rest of the system sucks, and really everyone else in the spectrum too. Of course the higher the frequency the better, but there are TONS of requirements of these on lower bands.

One solution I proposed on at least conventional systems is one-way amplification into the building, then voted receive. One voter site could in theory probably cover several small commercial buildings and/or a small area. This isn't a end all solution, but could work for smaller communities on lower frequency bands requiring in-building coverage.
Reply With Quote
  #12 (permalink)  
Old 04-16-2018, 10:17 PM
Member
  Amateur Radio Operator
Amateur Radio
 
Join Date: Apr 2008
Location: pittsboro in / mesa az
Posts: 399
Default

Quote:
Originally Posted by MTS2000des View Post
A large agency like where I work has a staff of 8 full time technical staff, one of us (me) is an ETA certified RFIM technician.
ETA has an Advanced RF Interference Mitigation (AIM) cert now. Did you take the class from Tom Dover or Ira Wiesenfeld?

Quote:
Originally Posted by MTS2000des View Post
Yet the FCC is too busy peddling spectrum to the telecom cartels and leaves the work to you, the end user/system manager, to figure out and deal with on your own.
I wondered what triggered this investigation.

Case Number: EB-FIELDNER-18-00026401
On March 9, 2018, in response to an interference complaint, an Agent from the Denver Office of
the Federal Communications Commission’s (FCC or Commission’s) Enforcement Bureau
(Bureau) confirmed by direction-finding techniques that radio signals on the frequency
463.3375 MHz were emanating from a warehouse at 18875 Bromley Lane in Brighton,
Colorado.

During an inspection, the Agent found that Sears Holdings (Sears) was operating
multiple transmitters on 463.3375 MHz. The Agent confirmed that the interference ceased when
the Sears equipment was unplugged. The Commission’s records show that the license issued to
Sears, under call sign WQCM387, for operation on the frequency 463.3375 MHz at this location
in Brighton, Colorado, expired in April 2015 and no renewal application is pending.
__________________
jay thompson / CETsr, GROL
COML, COMT trainee
KC9VTT / COML DMAT CA-4
milf CAN'T hear me, I've got private line
Reply With Quote
  #13 (permalink)  
Old 04-17-2018, 4:00 AM
krokus's Avatar
Member
  Premium Subscriber
Premium Subscriber
 
Join Date: Jun 2006
Location: Southeastern Michigan
Posts: 3,299
Default

Quote:
Originally Posted by MOTEX View Post
If you need to use BDAs, then you need to fix the REAL problem which is lousy repeater coverage.
...........
Most systems are poorly designed using the wrong tower locations
and the wrong atennas.
You have to use the towers/sites that you have. Most do not have the option to put another tower.

Either way, even with good tower coverage, there will still be dead spots, especially in large commercial structures.

Sent using Tapatalk
__________________
Generic radio geek, in southeast Michigan.
PSR-500, TM-742, TM-V71,TH-78, HTX-420, IC-2AT, IC-2E (clone), Pro-39, BC-235XLT, TK-290, XTS-5000
Reply With Quote
  #14 (permalink)  
Old 04-17-2018, 8:06 AM
Member
  Premium Subscriber
Premium Subscriber
 
Join Date: Jul 2006
Posts: 105
Default

Quote:
Originally Posted by MTS2000des View Post
Your agency should be involved in the process. Ever approached the fire chief(s) and discussed this with them? What will get their attention quick is when you mention the key words "LODD" and "IDLH" with "non-compliant life safety equipment".

It's what we do. We have 6 different fire agencies on our Astro 25 7.14 (soon to be 7.16) M-core simulcast system. We require that any BDA being installed in our coverage area forward the name and contact of the contractor installing it, the system design, FCC registration information, and then follow up with a review and walk through.

You can't leave it to someone else to do it because as you said, they lack the skill set.
We also require these things on BDA's that we are aware of. Unfortunately, the BDAs that interfere with us are installed at the request of and inspected by other agencies that happen to also be using frequencies near ours. Just because the BDA isn't intended to repeat our frequencies doesn't mean it can't still interfere with us.

And as I mentioned, a good amount of our problems with cell phone BDAs that are bought online and installed by a layperson without the slightest clue of what RF is.
Reply With Quote
  #15 (permalink)  
Old 04-17-2018, 9:17 AM
Member
   
Join Date: Sep 2008
Location: In the 'patch
Posts: 5,021
Default

Quote:
Originally Posted by 12dbsinad View Post
I am interested in starting a discussion about bi-directional amplifiers and interference (not related to bad installation practices).
I think you will find that interference is a side effect of poor installation practices

Quote:
Originally Posted by 12dbsinad View Post
BDA's are becoming common.
I think that this is becoming common because buildings are becoming more like Faraday cages as time goes on.

While my experience with BDA's is not from LMR, but from the Cellular side.

The single biggest issue is that the companies that sell and install them for cellular carriers here in Alberta simply do not have any sort of education on how to properly install them, and there is little to no support from the cellular carriers.

If I had to guess, there are likely tens of thousands of BDA's in operation in Alberta. They are from mobile amplifiers in vehicles to construction trailers, to work camps to plant sites. This is mostly due to poor coverage of the existing cellular networks, and the remote sites that tens of thousands of people work at every day.

Many of these BDA installs are so shoddy, it causes serious interference to the networks. There are a variety of reasons that this happens. The biggest issue is these installers are installing BDA's with out using spectrum analyzers, and they are causing the BDA's to immediately oscillate. BDA's used to feed BDA's using omni donor antennas that are not properly isolated for inside antennas. Having multiple BDA's on the same work sites, installed by different companies that just do not have the skills or knowledge to understand the impact their installs are having, because they do not have spectrum analyzers to see what is going on when they fire up their new BDA's.

BDA installations are all unique. No two installs are the same, and they need to be done methodically, and use best practices, by folks that have real world RF experience, and have the proper tools to ensure they are not causing harmful interference.
__________________
Interoperatablity is not a technology, it is an attitude!!!
Reply With Quote
  #16 (permalink)  
Old 04-17-2018, 9:51 AM
MTS2000des's Avatar
Member
  Amateur Radio Operator
Amateur Radio
 
Join Date: Jul 2008
Location: Cobb County, GA Stadium Crime Zone
Posts: 3,284
Default

Quote:
Originally Posted by speedway_navigator View Post
ETA has an Advanced RF Interference Mitigation (AIM) cert now. Did you take the class from Tom Dover or Ira Wiesenfeld?
Ira did my class at IWCE2017. 2 weeks or more of material in 3 days. My exam score was 98.
__________________
NO I will not help program your trunking radio. All opinions are exclusively those of the author and in no way reflect the position of his employer, contractors or other parties.
Reply With Quote
  #17 (permalink)  
Old 04-17-2018, 4:02 PM
MCore25's Avatar
Member
  Amateur Radio Operator
Amateur Radio
 
Join Date: Jun 2013
Location: Lone Star Republic
Posts: 3,040
Default

Quote:
Originally Posted by MTS2000des View Post
Ira did my class at IWCE2017. 2 weeks or more of material in 3 days. My exam score was 98.
I sat in on one of his Intermod classes at IWCE 2015...that was a good period of learning. Just took his GCT exams...told him afterwards he needs to update a few things.
__________________
If a repeater IDs and no one is on frequency to hear it, does it even make a sound? Yes, because KC5MVZ is monitoring you…
Reply With Quote
  #18 (permalink)  
Old 04-18-2018, 6:28 PM
Member
   
Join Date: Feb 2009
Posts: 508
Default

Quote:
Originally Posted by zz0468 View Post
Nope, I'm not buying that one.

In the course of reverse engineering one system's coverage problems, and develop the requirements for the replacement system, I once did a series of tests to determine typical losses in various types of buildings, as well as other operational circumstances such as operation with a portable on the hip with a speaker/mike.

Careful measurements were made in commercial and residential structures, concrete and steel high rises, to wood frame houses. Just to put things into perspective for you, I observed and measured tinted window glass that had 50 dB of loss at 800 MHz. That's ONE pane of glass with 50 dB of loss due to the metallic tinting.

Operating the radio while it's in a belt holster at hip level costs about 17 dB at 800 MHz. Just inside the first wall of a wood frame stucco house is about 10 to 15 dB.

Current operational requirements frequently now call for radio coverage inside commercial and residential buildings. It's "reasonable" to design system coverage sufficient to overcome the losses incurred by hip worn portables, inside a residential structure. but when you start throwing in 50 dB losses from insulated and reflective glass in steel and concrete buildings, a BDA is mandatory if inside coverage is required. And frequently it is.

Use of a BDA to augment coverage, especially if it's incorporated into new system design is considered good engineering practice, provided it's actually engineered, and not just thrown in.
Since i have actually been engineering and installing commercial radio systems for nearly 40 years, i' m quite aware of the limitations of 800mhz that' s why you don't use it if you have any other choices
450-470 does a much better job in buildings.
And 150-160 not only doesn't penetrate most buildings well, it is loaded with noise and interference to start with.
I have had to replace, move, and redesign dozens of repeater systems
all over the region that were as i stated using remote receivers, BDAs,
links, etc etc because the root cause of the coverage problem wasn't
addressed.
So in EVERY single case i was able to remove ALL the BDAs and remote receivers by simply fixing the REAL problem which was in fact
lousy repeater installations.
I have gone behind the best in the country and corrected the coverage
problems General Electric, Motorola, and Harris factory engineers failed to find.
And no, using BDAs instead of using the right frequencies, tower locations, and antennas is certainly NOT "good engineering practice".
Reply With Quote
  #19 (permalink)  
Old 04-18-2018, 7:28 PM
Member
   
Join Date: Mar 2010
Posts: 914
Default

The amount of money that gets spent on BDA's is crazy. Yet, they could use it to actually improve the current system or add more sites to infiltrate better, and in most cases can be needed anyway because street coverage could be somewhat lousy.

However, the lobbyist's (NFPA) come up with these crazy recommendations that somehow towns and city's are going to be able to have 100 percent coverage inside ALL new buildings by installing BDA's. This couldn't be farther from the truth. But, it gets written into city laws of new construction. All they do is "follow" without any knowledge about anything. If not installed properly (which more are not than are probably) all they do is cause more of an issue than they solve. They can turn lower frequency systems into even more of a "trash band" than it already is, and can oscillate no matter what the band.

The price of a properly installed BDA is tens of thousands typically (especially if not everyone is on the same band),per building, and only cover (maybe) the inside. If the guy with the gun runs out the back door into the abandoned mill next door, you're still screwed. you'd almost be better off with micro radio sites. At least you know that they'd be city owned and actually maintained, and probably cover a city block worth of buildings with decent interior coverage.

Last edited by 12dbsinad; 04-18-2018 at 7:38 PM..
Reply With Quote
  #20 (permalink)  
Old 04-18-2018, 7:42 PM
Member
   
Join Date: Feb 2007
Location: 175 DME, HEC 358° Radial
Posts: 5,590
Default

Quote:
Originally Posted by MOTEX View Post
Since i have actually been engineering and installing commercial radio systems for nearly 40 years...
I've been in the business about the same amount of time, in what is probably the single most complex RF environment in the world - Southern California. I'm sure you've earned the right to your opinion, much as I have.

Quote:
Originally Posted by MOTEX View Post
...i' m quite aware of the limitations of 800mhz that' s why you don't use it if you have any other choices
Well, now. It must be nice to live in an area where you actually get to pick and choose the piece of spectrum you'd like to operate in.

Quote:
Originally Posted by MOTEX View Post
450-470 does a much better job in buildings.
Yeah, I'd tend to agree with that. But, in crowded areas, there's probably no spectrum available to build a large system.

Quote:
Originally Posted by MOTEX View Post
And 150-160 not only doesn't penetrate most buildings well, it is loaded with noise and interference to start with.
It's an all around poor choice for an urban environment.

Quote:
Originally Posted by MOTEX View Post
I have had to replace, move, and redesign dozens of repeater systems all over the region that were as i stated using remote receivers, BDAs,links, etc etc because the root cause of the coverage problem wasn't addressed.
I've seen plenty of cases where the root issues weren't properly addressed, and BDA's had nothing whatsoever to do with those systems.

Quote:
Originally Posted by MOTEX View Post
So in EVERY single case i was able to remove ALL the BDAs and remote receivers by simply fixing the REAL problem which was in fact lousy repeater installations.
Wait... So, you don't like receiver voting, either? I'm trying to comprehend how arbitrarily removing two useful tools from your bag of engineering tricks is "good engineering practice".

You apply the right tool to the right problem. I'm glad you're able to manage to build enough proper sites to fulfill the coverage requirements, but I assure you, there are plenty of situations where that simply can't be done.

Quote:
Originally Posted by MOTEX View Post
I have gone behind the best in the country and corrected the coverage problems General Electric, Motorola, and Harris factory engineers failed to find.
What did you do, beat the RF into submission so it just goes exactly where you want it to?

Quote:
Originally Posted by MOTEX View Post
And no, using BDAs instead of using the right frequencies, tower locations, and antennas is certainly NOT "good engineering practice".
Would you really rather build a 3 million dollar site when a $75K BDA installation properly done will solve that part of the puzzle?

Ok, here's an engineering challenge... Imagine a 10,000 to 20,000 square mile coverage area. Yeah, that large. 5 million population, terrain from below sea level to about 12,000 feet. Rural desert, to alpine forest, to dense urban area. Much of the land is protected habitat where you can't build new sites. You have budget limitations, and no spectrum choice - it's gonna be 700/800 MHz. Interoperability with neighboring agencies is a requirement. Because of your own stubbornness, you can't use receiver voting, and you can't use BDA's. The coverage requirement for the entire service area is 95/95, with a portable on the hip. And it damned well better work inside the provided list of public and private buildings.

The challenge is to stay on budget, and meet the timelines. Watch your long term maintenance and site rental budget. It's tight!

Ready, set, go!

Reply With Quote
Reply

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On



All times are GMT -5. The time now is 12:29 PM.


Powered by vBulletin® Version 3.8.2
Copyright ©2000 - 2018, vBulletin Solutions, Inc.
All information here is Copyright 2012 by RadioReference.com LLC and Lindsay C. Blanton III.Ad Management by RedTyger
Copyright 2015 by RadioReference.com LLC Privacy Policy  |  Terms and Conditions