In-house cellular repeater causing severe reception problems

[KI4LIV]

A few months ago my company decided to install a privately owned cellular repeater to help with cellular reception here in the building.

It has provided us with literally zero benefit on the cellular reception, but has caused one hell of a mess when trying to monitor my local EDACS system.

I first thought it was a problem with shielding or even RF coming in through the speaker leads on my Pro-97, so I brought in my MP-A radio and I am still hearing this infernal whining noise coming through with every transmission. No reduction in the noise , even with the superior shielding and filtering that the MP-A has !

Does anyone have any suggestions of how I can get around this? I've tried turning on the attenuator on the Pro-97, but that did nothing more than reduce my reception, giving me unreadable scratch-laden audio.

Obviously, since radio monitoring is not one of my job tasks (but is allowed since I have a private office), the company couldn't give a steaming pile of gerbil vomit whether or not I can listen. Oddly though, even though they spent $5k and then some on this piece of hardware that is provide us with no benefit other than excessive RF exposure (ok - so I might be stretching that a bit!), they will not take it back out or return it.

Thanks so much in advance!

 

[Bote]

WARNING about cellular repeaters/extenders

Your company might care more than a pile of gerbil vomit when the FCC knocks on their door with U.S. Marshals behind them.

These cellular bi-directional repeaters are a nuisance that is growing worse, and they are giving the cellular companies fits trying to run down interference complaints. Here in Fort Lauderdale the problem comes and goes as big yachts berth here for a couple days, bringing with them the interference from improperly installed range extenders. Sometimes they can be notified and the problem solved, other times it's too late.

You are correct that they do not extend range like that, because the re-radiating antenna feeds back to the donor antenna on the other side of the box and the unit oscillates, generating the broadband noise that is wiping out your reception, along with deafening reception at nearby cell sites.

You'd better believe the cellular companies are on the warpath about this, so if your building owner doesn't take notice he will likely be facing some heat once they pinpoint where the interference is coming from. That might solve your problem. It's funny how large communication$ companies and police & fire departments don't take kindly to having their communications disrupted by rogue installations like that.

Of course, you might want to make a friendly suggestion that saves him all this trouble...I'm just sayin.

 

[wlmr]

You'd better believe the cellular companies are on the warpath about this, so if your building owner doesn't take notice he will likely be facing some heat once they pinpoint where the interference is coming from. That might solve your problem. It's funny how large communication$ companies and police & fire departments don't take kindly to having their communications disrupted by rogue installations like that.

Of course, you might want to make a friendly suggestion that saves him all this trouble...I'm just sayin.

Bote is correct. And if as you are stating the cellular company wasn't the one to do the install it's already against FCC rules. If your boss doesn't accept your suggestion, a couple discrete calls to the local cellular provider's technical repair staff will probably get a lot of attention focused quite quickly.

 

[KI4LIV]

Definitely not installed by a cellular company, unless our in-house network people and in-house maintenance people are working on the side with them!

 

[Bote]

Definitely not installed by a cellular company, unless our in-house network people and in-house maintenance people are working on the side with them!

Yep, that's pretty typical. People see these things for sale on web sites, order them, and slap them in not realizing that a lot more engineering work needs to go into it.

One company has already been forced to stop selling them in the U.S., but yacht owners buy them in the Caribbean or elsewhere and bring them in already installed. Interference to go! WOO HOO! At least your building isn't moving anywhere (I hope!)

How about shooting me a private e-mail with your phone number and I can put you in touch with somebody who can talk to you about this to size up the situation. You'd be doing a whole bunch of people a big favor, they just don't know it yet.

bote.prodigy at gmail . com

Thanks.

 

[fineshot1]

A few months ago my company decided to install a privately owned cellular repeater to help with cellular reception here in the building.

It has provided us with literally zero benefit on the cellular reception, but has caused one hell of a mess when trying to monitor my local EDACS system.

I first thought it was a problem with shielding or even RF coming in through the speaker leads on my Pro-97, so I brought in my MP-A radio and I am still hearing this infernal whining noise coming through with every transmission. No reduction in the noise , even with the superior shielding and filtering that the MP-A has !

Does anyone have any suggestions of how I can get around this? I've tried turning on the attenuator on the Pro-97, but that did nothing more than reduce my reception, giving me unreadable scratch-laden audio.

Obviously, since radio monitoring is not one of my job tasks (but is allowed since I have a private office), the company couldn't give a steaming pile of gerbil vomit whether or not I can listen. Oddly though, even though they spent $5k and then some on this piece of hardware that is provide us with no benefit other than excessive RF exposure (ok - so I might be stretching that a bit!), they will not take it back out or return it.

Thanks so much in advance!

Although the other posters are probably correct about the "In-house cellular repeater" issue I think everyone has also over looked the fact that this device has probably over loaded your receiver front end which I beleive may be the actual cause of your problem. If this is the case and the device winds up staying in place (for what ever reason) your gonna have to live with it cause this is a common problem with scanner receiver front ends and the proximity of these devices. Good luck....

 

[zz0468]

Although the other posters are probably correct about the "In-house cellular repeater" issue I think everyone has also over looked the fact that this device has probably over loaded your receiver front end which I beleive may be the actual cause of your problem. If this is the case and the device winds up staying in place (for what ever reason) your gonna have to live with it cause this is a common problem with scanner receiver front ends and the proximity of these devices. Good luck....

Rather doubtful, actually. The usual result of an amplifier like this installed improperly is self oscillation because of poor antenna isolation.

 

[Universaldecoder]

Stay after work one day. Take some aluminum tape, wrap it fully around the radiating antenna, ground it to the antennas base, and cover it neatly with black dull electrical tape for now. It'll work as a shield in disguise.

Or if the antennas unscrew. remove them and with snips, cut off the contact pins.

Basically you want to discretely remove the input and output signal.

However the best thing you can do is to take it apart, snip the power connections internally, put it back together, wipe off your finger prints, and neatly put it back.

 

[gmclam]

If there is so much signal from the cell repeater that your scanner is overloaded even without an antenna connected, I think there's no hope. It's hard to say from here whether or not it would do any good, but assuming my 1st statement isn't true, my thinking is that you want to increase the signal level of the DESIRED signals (the EDACS trunk) over the undesired source. To do so you'd need a HIGHLY directional antenna, pointed at the EDACS site and away from the cell repeater.

 

[fineshot1]

Rather doubtful, actually. The usual result of an amplifier like this installed improperly is self oscillation because of poor antenna isolation.

Ok - I made an assumption that it was properly installed, and your making an assumption that it was improperly installed. Since neither of us know the actual parameters of the install we both took a shot in the dark.

 

[Bote]

Ok - I made an assumption that it was properly installed, and your making an assumption that it was improperly installed. Since neither of us know the actual parameters of the install we both took a shot in the dark.

Based on my experience, it is highly likely that this is a Rube Goldberg-type install. It is unlikely that an information technology shop would have a spectrum analyzer or antenna network analyzer at their disposal to test the effectiveness of their installation. It is unlikely that they would have personnel who are well-versed in radio theory and practical applications.

The o.p. has already stated that his i.t. guys installed it. Being in the communications business, I have seen some pretty shoddy work (even from those who should know better).

Based on all the available evidence plus my personal experience in the field, my assumption is most likely closer to the truth. I have no reason to give them the benefit of the doubt given how many of these noise makers have been popping up all over the place. That might come to a screeching halt soon. Watch the news.

 

[zz0468]

Ok - I made an assumption that it was properly installed, and your making an assumption that it was improperly installed. Since neither of us know the actual parameters of the install we both took a shot in the dark.

Yeah, I made an assumption, but not as wild an assumption as you might think. It can take a great deal of engineering, including antenna isolation measurements, donor signal strength measurements, and so on. "IT" people play notoriously fast and loose with RF. But with these things, you simply can't. They have a LOT of gain, and if you don't know what you're doing and install them improperly, they'll 'sing'. The amplifier turns into a nice high power oscillator with noise and spurs occupying the entire system passband. Even a professionally engineered and installed system can be cantankerous and finicky, and require very careful alignment.

These things that the IT guys throw in are nightmares. I've had to DF several over the years and threaten FCC action to get them turned off. Unless they're authorized by the licensee (i.e. the cellular provider) they are not legal. Unless they have filters to limit service to the specific frequencies associated with the licensee, they can have serious detrimental effects on other users systems.

 

[FlashSWT]

So...since we're on the subject, what are y'alls opinions on a device like this:
http://www.wi-ex.com/

What effect would it have on scanning with an indoor antenna?

.

 

[zz0468]

So...since we're on the subject, what are y'alls opinions on a device like this:
http://www.wi-ex.com/

What effect would it have on scanning with an indoor antenna?

Maybe nothing, and maybe it could raise the noise floor nearby to a point where a scanner can't hear weaker signals. All in all, however, these things are a bad idea for consumer use. Yeah, they likely can help a cellphone user in some cases, but unrestricted use on signal boosters by the general public is a Bad Thing. I've had to chase things like this down because there were oscillating on system input frequencies and interfering with public safety frequencies.

 

[N4DES]

FCC Rules Part 90 and Part 22 are very clear as to who can install and operate a BDA, and it's only the licensee.

 

[Bote]

Junque

So...since we're on the subject, what are y'alls opinions on a device like this:
http://www.wi-ex.com/

What effect would it have on scanning with an indoor antenna?

Junque or junk. Either way, they'll have your money and you will have your very own noise generator deteriorating your receive performance. Such a deal!

Snake oil is still snake oil, no matter how fancy the bottle in which it is sold.

The thing with this box is that if you can arrange an outdoor donor antenna to hook to this box, then you can hook the same outdoor antenna to your scanner and get it all over with. And get decent receive performance to boot, assuming your scanner is not overloaded simply by hooking it to an outdoor antenna.

Save your money.

 

[jim202]

The better bi directional amps have adjustable gain. If this system does have the gain
adjustment, I would turn it way down to bring the system back into a state where it
might just start to work the way it was designed.

Many of the BDA systems that are installed in buildings don't have enough isolation
between the antenna that is looking at the cell doner site and the inside radiation
antenna.

Jim

 

[zz0468]

The thing with this box is that if you can arrange an outdoor donor antenna to hook to this box, then you can hook the same outdoor antenna to your scanner and get it all over with. And get decent receive performance to boot, assuming your scanner is not overloaded simply by hooking it to an outdoor antenna.

If the amplifier at his location is bi-directional, there's going to be LOTS of signal on both antennas. A bi-directional amplifier can't share an antenna with a receiver.

 

[WA4MJF]

Looks as if you'd just use a duplexer, at cell phone frequencies they would not be very
large. Otherwise, try a greater antenna separation, remember it takes more
separation horizontally than vertically. I don't know if it would be possible to
seperate the input and output frequencies more or not.

 

[Bote]

If the amplifier at his location is bi-directional, there's going to be LOTS of signal on both antennas. A bi-directional amplifier can't share an antenna with a receiver.

No, I meant forget about the bi-di amp completely and just put up an antenna suited to the purpose in the same spot where he would have placed the donor antenna for the bi-di amp. Saves money, prolly works better. For everyone.