Boston TV Signals Disrupting Police Radio in NJ

jeffy124 writes "WCVB, a digital TV station in Boston, is disrupting police radio communications in South Jersey. It seems that under certain weather conditions, the signal reaches here travels 270 miles (it's normally 50) and blacks out the police frequencies, making communication between officers and from 911 call centers impossible. The article seems to suggest that as more TV stations go digital, more small-town police radio will be affected, as the digital signal is significantly stronger than analog. Insert Joisey-joke here."

Comments

I think it's a safe bet...

[NotAnotherReboot]

I think it's a safe bet that we'll see more donut commercials on digital television broadcasts- it ensures that it reaches the best possible demographic that will be influenced by donut commercials (cops, of course).

Joisey Joke

[Anonymous Coward]

NJ got all the toxic waste dumps. You see, California drew the short straw and got all the lawyers.

Re:Joisey Joke

[Lucas Membrane]

It's true about NJ mosquitoes. They've adapted and actually are attracted to mosquito repellant. When a busload of tourists comes to the Jersey Shore from NYC loaded with mosquito repellent, the mosquitoes go into such a frenzy that they actually bite the picture of the greyhound on the side of the bus. Within a few hours, the bus is so swollen that it can't fit back through the Lincoln Tunnel.

It's called

[pa-guy]

tropospheric ducting.

Joisey Joke?

[thesolo]

Ok, this is slightly OT, but speaking as someone who lives in Southern NJ, I would like to state for the record that no one around here speaks with that type of accent. We all pronounce Jersey with the letter R, thanks!

Most people have a large misconception about New Jersey, especially thinking that it all looks like Newark, every woman has huge hair and long fingernails, and that none of us pronounce the letter "R". While this isn't entirely untrue (head up to Northern NJ to see what I mean), it does not describe the area of NJ being affected by the Boston signals. As I always say, they should split up Northern & Southern NJ, and combine the Dakotas. :)

Back on topic, I saw this story on the local news here tonight. It's a very big problem, as peoples lives can potentially be at stake. This is something we will be seeing a lot more of in the future; we already have frequency problems with 802.11, and now it seems that TV broadcasts will be continuing the trend.

Not the only occurence

[Papa Legba]

I work for a PBS station in VA, WHRO. We are currently being sued by a station WBOC-TV Salisbury, Md to stop the rollout of our Digital TV because it disrupts their signal on the Chesapeake side of the water.

From what I understand of the problem their were bad assumptions made by the FCC when it came to the digital signal.
1. That it would not bounce and doppler like analog signal does. Well it turns out it is even more prone to it than analog was due to the higher frequencies and watages involved.
2. That this would not affect a $Properly setup atena. Seems reasonable until you find out what the variable properly is. Apparently the FCC does not care about interference unless the atena is aligned directly towards the sending tower (that never happens and varies from channel to channel) and that it is not higher than 30 feet (one story home. Any deviation from that and it becomes your problem, not theirs.

This is also not the first case of this to happen. Their are previous cases in california and milwauke. Read more
here

This is going to crop up as more and more channels go digital. You will start seeing it reported more as stations start to battle each other. The sad part is that most likely the FCC will wash their hands initally and the airwaves will become as if the FCC does not exist.

Re:Not the only occurence

[Skuld-Chan]

That it would not bounce and doppler like analog signal does. Well it turns out it is even more prone to it than analog was due to the higher frequencies and watages involved.

Somewhere a ham radio operator is crying.

I think the term you are looking for is propagation (the way signals travel through the ether) :). In general doppler shift isn't that much of an issue unless the transmitter is moving very fast (like a low earth orbit satellite)

I have no idea what frequencies digital tv stations operate on, but in general on uhf tropospheric ducting is pretty rare - at least where I live.

Where analogue tv channel 2 (around 57 mhz) long range propagation is pretty common, but thats not tropospheric ducting - thats sporadic e layer propagation.

Past tv channel 7 tropospheric ducting is relatively common.

Past tv channel 13 tropospheric ducting still happens, but its not nearly as common.

I don't see why the mode would matter - I think digital television is a spread spectrum signal. If done right you should be able to operate other ss devices in the same frequency space. Narrow band radios recieve ss signals as low background noise typically - so that should be an issue. I wonder what the real interference problem is?

geez!

[jeffy124]

Ok, I'm the submitter. I see a few posts denouncing the "Joisey" reference. I'm from NJ. It takes a sense of humor to live in NJ. I know that SJ is vastly different from the smokestacks of Newark.

Am I the only person who lives in NJ with a sense of humor?

(oh, and for the record, I live between exits 3 and 4)

Gratuitous link

[Anonymous Coward]

Just in case you would like to know what tropospheric ducting is.

Tropospheric Ducting Forecast Maps

[KernelSanders]

VHF / UHF Tropospheric Ducting Forecast Maps

These maps graphically display unstable signal areas.

Quote from the website:

The areas noted in the forecast have the necessary atmospheric conditions to produce tropospheric bending of UHF or VHF TV and radio waves. Tropospheric bending extends the range of stations well beyond their normal limit. Distant reception along straight line paths becomes possible..though the longer the path, the higher the Index required. The pursuit of distant stations is called "DXing".

Re:Same frequencies?

[damiangerous]

The "real story" would be the article. Which contains the answers to every single one of your questions.

Re:Digital TV

[Mitreya]

I have nothing against DTV/HDTV.
I did get the impression that it is being forced down our collecive throats since it has not been adapted quickly enough by the market.

I feel that the regulations are being applied to the *wrong* industry. Wouldn't it be much better to mandate that all vehicles must be electrical or hybrid by 2007? As much as I like my car, I can see the advantage of such law. but TV phase out? for what? for Hollywood quality content that they have been withholding? :)

Re:Same frequencies?

[MisterFancypants]

The links go to articles? Fascinating!

Minor corrections...

[KC7GR]

From the /. article header...

"The article seems to suggest that as more TV stations go digital, more small-town police radio will be affected, as the digital signal is significantly stronger than analog..."

Actually, the type of modulation (digital or analog) has little to do with the signal "strength" (which is a function of transmitter power output, transmission line losses, and antenna design and orientation).

Now, with that said, digital modulation, being much closer to a square wave than an analog voice signal, is much richer in HARMONICS than said analog signal.

I've lost count of how many times I've heard interference from digital paging transmitters bleeding into ham radio repeaters. The harmonics from the digital modulation mix with the transmitter's carrier, and that of whatever other transmitters happen to be on the same hilltop, and close to the same frequency range. It sounds awful, and it looks even worse on a spectrum analyzer screen.

The problem may be correctable through (as others have pointed out) better receiver design, in terms of filtering, and good installation practices being followed where the transmitter and antenna system are concerned. Good filtering and modulation techniques at the transmitter end won't do any harm either.

Insert Joisey-joke here.

[evilviper]

Insert Joisey-joke here.

Geena Davis: "Easy, sport. I got myself out of Beirut once, I think I can get out of New Jersey."

Sam Jackson: "Yeah, well don't be so sure. Others have tried and failed... The entire population, in fact."

Re:Ok, that's it, I am suing

[MajroMax]

"Slashdot, new for nerds, stuff that matters"

First there was the pumpkin PC, then the Dune book, and now a story that takes pertains only to NJ. I am officially suing slashdot for breach of contract.

You must be new here.

Allocations

[rfg]

A lot of innacurate information has been passed around here.

UHF communication frequencies generally go from 450-470 mHz and were fully populated years ago. What the FCC did is to allocate certain UHF TV channels to communications, in the 470-512 range; ie TV channels (not cable channels) 14-20 for communications use in certain areas. The areas in question are laid out in a plan, so that in some areas a certain channel is used for TV and and in some areas that same channel is used for communications.

This came about because in a given area you cannot have adjacent TV channels used by TV or they interfere with each other. Also, UHF TV was never really popular with broadcasters and many channels were loped off on the upper end (ch 70-88 as I recall).

Thus it is perfectly in accordance with the FCC plan to have Channel 20 allocated to TV in Boston and to communications in Southern New Jersy. Up to now, however, channel 20 was never used in Boston, it was empty and now has been allocated to digital TV.

Analog TV stations must convert to digital by a certain date (2006, but keeps slipping....). During the interim period, the station may transmit Analog on its present channel, and digital on the new channel. This is precisely what WCVB is doing. Eventually the station will be strictly digital on Channel 20 and the Analog VHF transmission will terminate.

East coast atlantic tropospheric ducting is common and radio hams and others are well aware of it; I am surprised the FCC did not take this into account when they allocated the channels. If I had to speculate, I would say that the FCC will require WCVB to reduce power, use a directional antenna or change channels - which may be tricky. This will be fertile ground for hordes of lawyers.

Re:Did someone say 'Joisey joke'?

[Loki_1929]

Score 5 Funny?

I'm guessing the moderators who modded that up have never actually been to New Jersey. Now, for one thing, the Meadowlands (up north close to NYC) is the only place that's even remotely smelly or of poor conditions in NJ that I've seen so far. Much of southern NJ was made up of small farming communities until recently when actual townships started forming. Most of NJ is now just that; small townships with hardly anything in between but trees, connected only by small (two lane) roads. I just moved to NJ a few years ago, and I'm not offended by comments - just the ignorance that their content shows. If you want to make a joke, call the people here simple, or make a comment about how almost everything is closed after 6pm, or how there's so much farmland. There's no accents in New Jersey; you're thinking of certain sections of NYC. These are (for the most part) normal, simple people who are MUCH friendlier and happier than the people from the DC-metro area. No one here says "joisey", we say "jersey". I must admit, however, that I was a bit surprised when I moved here from Maryland and couldn't find someone with any accent for a while.

Oh, and by the way, our gas is cheaper than most places in the country, and it's full service everywhere (state law). When my relatives in MD were paying $1.90 for gas, we were paying $1.25. NJ isn't such a bad place when you actually take a turn off the NJ Turnpike.