More on digital danger

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brey1234

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New tests to assess digital-radio performance in fireground-noise environments have been delayed until the spring, according to an official participating in the process.
D.J. Atkinson, lead electronics engineer for Public Safety Communications Research (PSCR), said his unit — a joint effort of the National Institute of Standards and Technology (NIST) and the Institute of Telecommunications Services (ITS) — likely will conduct the tests in April. Late last year, Atkinson said he hoped the testing would occur this month, but an extended comment period has delayed the start of testing by at least two months.
http://urgentcomm.com/mobile_voice/news/fireground-radio-tests-delayed-20100216/
 
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N_Jay

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Why is a delay in the tests to make them more manageable labeled "More on digital danger"?
 

cifd64

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I agree with rdale, and though it is kind of obvious. Digital on the fireground is a bad idea for the same reason duplex is not recommended on the fireground. Too many moving parts. Using digital at a traffic stop works gereat, i am sure. But when a mayday goes out and the channel gets log-jammed with traffic, (even the most disciplined firefighters get a little anxious when a brother goes down) digital fails. Especially in the basement of concrete buildings. As far as it working for public works, plowing a street aint making a push into a bedroom fire.

Simplex ONLY! That should be the mantra of fire unions and firefighters everywhere.
 

jackj

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Noise

They aren't in the basement of cement buildings...
Or standing next to diesel engines running big pumps. Or screaming people. Or noisy, collapsing roofs (walls, floors). Or talking fast and indistinctly. In short, there is a big difference between a quite squad car and noisy, confusing fire scene.
 

cifd64

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The thing to remember is the article is pushing noise-canceling technology, as well. They make it seem that blocking the sound of deisel engines will fix the issue of poor penetration in intense situations.
 

jackj

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Digital problems

The thing to remember is the article is pushing noise-canceling technology, as well. They make it seem that blocking the sound of deisel engines will fix the issue of poor penetration in intense situations.
Except that noise canceling mics won't cancel noise that comes from behind you in the open. Also it does nothing to solve the problem of someone in trouble shouting into the mic. Like you point out, 800 Mhz behaves like light and doesn't pentrate dense materials very well and that is a problem no amount of spin or massaging of the data will fix.
 
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N_Jay

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I love it.

From a delay in testing to make sure the process is manageable,

to,

Digital is no good,

to,

Repeaters are no good,

to,

800 MHz is no good.


I am thinking we need to get back to 30-50 MHz AM!

"Two hundred years of tradition unhampered by progress."
 

jackj

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News flash

I love it.

I am thinking we need to get back to 30-50 MHz AM!
"
You're wrong, 30-50 MHz public service has always been FM. However 1700 KHz was used for a lot of years and that was AM. Lets go back to that, no scanners needed just a good re-tuned AM radio. hehehe
 

SCPD

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It's amazing that the fire unions can't seem to work digital radios but the cops and public works people use them everyday. Many fire depts. are using digital and have no issues.
Many cops aren't also in the midst of a roaring fire, wearing bunker gear and SCBA either. Monitoring fire communications during a working fire, it is sometimes hard to to understand what those wearing SCBA are saying on analog, I can only imagine what those same persons sound like on a digital system.

Remember, lose 1-bit of data in the communication in digital radio, and things can sound very different.
 
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N_Jay

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You're wrong, 30-50 MHz public service has always been FM. . . .
You really should KNOW what you are talking about before declaring someone is "Wrong" in a "News Flash"

If you look back far enough you will find early low band (and maybe even high-band) was AM.

Some companies even produced radios that could be converted from AM to FM.

From: Motorola History - Early Police Radios - Explore Motorola Heritage - About Motorola - Mobile - Galvin Manufacturing - Heritage - Design - Concept - Engineering - Two-Way Communications - Public Safety

"Mobile two-way communications
Paul Galvin assigned his chief engineer, Don Mitchell, to develop a radio transmitter for the car. In August 1939, Galvin Manufacturing introduced the Motorola model T6920 AM mobile transmitter, which broadcast in the 30-40 MHz range. A model P6912 VHF receiver and base station equipment soon followed."

Now say write "I'm Sorry" 500 times on the blackboard, and when you are done wash all the boards and clean all the erasers.
 
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N_Jay

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Many cops aren't also in the midst of a roaring fire, wearing bunker gear and SCBA either. Monitoring fire communications during a working fire, it is sometimes hard to to understand what those wearing SCBA are saying on analog, I can only imagine what those same persons sound like on a digital system.

Remember, lose 1-bit of data in the communication in digital radio, and things can sound very different.
Yes, and the issue (and testing) is driving the industry very nicely.

Several companies have made significant progress in noise reduction and intelligibility.

As for losing 1 bit, you are incorrect. FEC (Forward Error Correction) takes care of many bit errors.
 

colby4601

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Many cops aren't also in the midst of a roaring fire, wearing bunker gear and SCBA either. Monitoring fire communications during a working fire, it is sometimes hard to to understand what those wearing SCBA are saying on analog, I can only imagine what those same persons sound like on a digital system.

Remember, lose 1-bit of data in the communication in digital radio, and things can sound very different.
What is that supposed to mean?
 

James_Bond_007

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You really should KNOW what you are talking about before declaring someone is "Wrong" in a "News Flash"

If you look back far enough you will find early low band (and maybe even high-band) was AM.

Some companies even produced radios that could be converted from AM to FM.
i can attest to the fact that Low and Hi Bands were AM back in the 50's. I had some 152/158 Mhz motorola Research line radios from a defunct local taxi company and they were AM and only 10 watts i beleive.
 

Squad10

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Anybody know of a specific fire agency that used AM for fireground or general communications in the past?
 

James_Bond_007

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Anybody know of a specific fire agency that used AM for fireground or general communications in the past?
might have to look to some of the larger departments in major metro areas history. they would have been most likely to adopt new tech as it came out.

i would say most departments did not even adopt radio's until the 60's due to the cost versus their available budgets and by the 60's it was all FM.
 
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N_Jay

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Anybody know of a specific fire agency that used AM for fireground or general communications in the past?
I doubt it. Most fire agencies did not even have portable radios for anyone other than officers until well into the 1980's or later.
 
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James_Bond_007

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look into the history of agencies in california. LA Fire would be one that was most likely to adopt new radio technology as it came available.

if anyone was using AM it probably would have been them.

if i have some time i will do some digging and see what i can come up with.
 
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