This could also effect scanners

[n4voxgill]

NPSTC Current Newsletter

New Source Of Cell Phone Interference
Barry H. Luke, Deputy Chief of Fire Communications for Orange County (Florida) Fire Rescue, was surprised to learn that a source of radio channel interference in their Communications Center was personal cell phones. “Radio Services had been working for several weeks, trying to track down the source of some unusual interference in the 800 MHz system,” he says. “They asked us to do some testing with cell phones at and around the new radio consoles.” Chief Bruce Zwegat tested different types of phones and at different locations. The results of the testing demonstrated that a ringing cell phone will cause interference on the radio channel even if it is on vibrate and not located adjacent to the console. For example, interference occurred if the cell phone was in a purse on the floor next to the console. “Any conversation on the cell phone caused significant interference to the operator's outbound radio transmissions on any talk group that they used. The worst interference on the radio system was caused by the cell phone ringing, even if it was not answered by the operator,”

Communications Center instituted a new policy to ensure that radio communications are clear in the future. Personal cell phones may no longer be used or carried in the Communications Center, including a personal cell phone at the work station that is set to
vibrate. Signs have been posted in the dispatch area directing visitors and other employees to step away from the area if their phone rings or if they need to place a call.
Radio Services and the radio system vendor are continuing to examine the problem, and are reviewing to what extent shielded cabling might be able to reduce or eliminate the source of the interference.

 

[cellblock776]

No suprise there. My cell phone always interferes with my scanner when I'm monitoring the local 800MHz TRS. I use a Pro-93 to listen while at work. About a second before my cellphone rings I hear a buzzing static through the speaker of my scanner. It continues until I end the call and hang up the phone.

 

[flyingwolf]

lol I can tell I am about to get a phone call on my cell before it ever rings. About 1.5 seconds before it rings my computer monitor flickers a little bit.

But cell phones make billions a year. If they cause interfeerance they MAY fix it in the next version.

 

[n4voxgill]

my phone is a qualcom G3 and it does not effect eitther monitor or scanner. I notice the article said "personal owned" cell phones. I know the county uses only Nextel so I wonder if those are not causing a problem.

 

[Audiodave1]

Hello,
Nextels are the worst offenders of the lot.
Testing has showed that they emit almost 3w PEP (2.8 exactly) while ringing.
I can't tell you why they produce these huge output levels but I know it gets into most poorly grounded / shielded gear in my world of pro audio.

These are devices that are only supose to produce a max output of .6w in any state...it just isn't the case...

I'm done ranting now.
Dave

 

[SAR923]

This all seems a little odd to me. I've used my cell phone countless times on duty and I'm sitting next to a console with a VHF, UHF and 800 Mhz radio as well as a Pro-96 scanning other trunked systems. I've never experienced any interference and have even been talking on the radio with the cellphone in my ear and still not seen any interference or crosstalk. I'm still using an ancient Nokia 6100 though so I wonder if newer models aren't more prone to causing interference. Still, it seems like a properly set up comm center wouldn't be able to be bought down by just having a ringing cell phone in the room.

 

[BaLa]

nothing new to me either..


My cellphone used to mess with my CRT Monitor all the time when it did ring.
I can hear a buzzing/staticy sound on my speakers (scanner, car speakers or computer speakers).


I've always thought that was normal, and after getting used to it I actually kinda like it. Since it 'announces' the call before it rings.

 

[N_Jay]

iDEN is worse with its charicteristic 11 Hz buzz.
TDMA is usually heard at 60 Hz, and GSM is 50 Hz.
CDMA phone typically do not cause an issue.

The problem is the noise generated during the start and stop of the transmission of each digital frame. It is not the RF signal during the transmission.

As for trying to measure these phones in PEP? Don't expect them to equate to their average power ratings.

 

[kc8bdk]

Audiodave1 I second your comments, however even if your using good cables, the sound bleeds in.

I was doing a convention in Orlando several years ago and had a person standing next to me with a nextel. The Secret Service was there because George Bush Sr. , Collin Powell and Janet Reno were ALL due to be speaking later in the day. All of a sudden there was this horrible noise thru the system mostly the subs.

let me tell ya, there were a LOT of hands moving very quickly twards radios and I am sure twards guns.

I took the phone, turned it off, and all was good. Thank goodness it was during soundcheck and not during the show!!

Paul aka SoundGod1

 

[nmfire10]

This is breaking news???? STOP THE PRESSES!!! Those phones have been doing that since the day they were invented. They are just now figuring this out???????

And I'm still wondering WHY anyone would think that puttin a phone on vibrate would stop RF interference?

 

[jred184]

removed

 

[N_Jay]

Everytime just before my cell rings my (computer)monitor would flicker and the speakers make a weird buzzing noise.

I also had one of those fx lights that are supposed to light up to the beat of the radio. My cell phone would light it up if you held it right next to it.

Since we have already been down the road that different types of phone act differently, why don't people al teast mentiuon the type of phone when they comment about it? :roll:

 

[N_Jay]

Audiodave1 I second your comments, however even if your using good cables, the sound bleeds in.

Good grounding and sheilding is not just about cables!! :roll: :wink:

Microphone lines are very sensitive.

In broadcast you use ballanced lines as much as possible.

Some equipment is just sensitive by design (unintentional design!) :evil: :wink:

 

[PhilJSmith67]

My personal observations are that the Blackberry units are absolute worst offenders. The most prominent provider of support for these devices in the Chicagoland area is Cingular. I am unsure if the Blackberries operate on Cingular's TDMA network, or if they're GSM (which is now also owned by Cingular). Nevertheless, those units even interfere with *corded* phones in close proximity, not to mention monitors and speakers. Second worst? I would have to say Nextel iDEN phones are nearly as bad if we're talking specifically about how they affect 800MHz communication, but they're not quite as offensive toward most non-800MHz devices.

 

[N_Jay]

My personal observations are that the Blackberry units are absolute worst offenders. The most prominent provider of support for these devices in the Chicagoland area is Cingular. I am unsure if the Blackberries operate on Cingular's TDMA network, or if they're GSM (which is now also owned by Cingular). Nevertheless, those units even interfere with *corded* phones in close proximity, not to mention monitors and speakers. Second worst? I would have to say Nextel iDEN phones are nearly as bad if we're talking specifically about how they affect 800MHz communication, but they're not quite as offensive toward most non-800MHz devices.

The issue is wiuth the radio portion, so a iDEN Blackberry will be like an iDEN phone, and a TDMA Blackberry will be like a TDMA phone, same for GSM, and CDMA.

I doubt that they are any worse.

Of course these are near field effects so minor changes in power level, antenna efficiancy, antenna placement, ect. will also have an effect.

Just curious? In coming up with your conclusion, just how many tests did you do? :wink:

 

[PhilJSmith67]

I began my post by saying "personal observations," not formal tests. Nevertheless, I can assure you that the sampling was well into the dozens of occurrences.

I fully understand that the TX sections, frequency range, antenna, TX power and digital modes are the focus, not the features and functionality beyond. That's why I stated that I was unaware of the digital mode being employed by the Blackberry units in our service area. If they are all TDMA, then I would expect TDMA phones to have similar effects. Not necessarily identical, but similar. I don't know if the Blackberrys on the Cingular/Chicago system are TDMA or GSM. I'm fairly certain they're not iDEN though, since Cingular leases the use of Sprint and (formerly) AT&T's towers in the area, which are TDMA and GSM, respectively.

I know seven people with Blackberry units through Cingular/Chicago. They all cause more trouble to nearby equipment than anyone I know with Nextel phones. It's a significant enough difference that formal testing would only have identified the degree of difference, not if there was a difference itself. They all notice it as well, and they know they can't leave their Blackberry handhelds near speakers, monitors, even the PBX phones at work. There are even more people with Nextel phones at work, yet they haven't had nearly the same degree of issues, although there still seems to be more effect from them than Verizon/CDMA phones.

Again, these are my personal observations, not a scientific study. Your actual mileage may vary.