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Weather Monitoring Frequencies Subject to Pollution
jd writes "In a case of technology vs. technology, the ICU (the body governing the use of radio frequencies around the globe) has been asked to secure radio frequences used for weather monitoring. In-car radar, mobile phones and other commercial and military applications are now using these same frequencies. However, weather satellites can't simply be re-tuned. There is only one very narrow band that detects water vapor but not liquid water, for example. This frequency has been sold to developers of car radar systems. The more this happens, the less useful weather radar and weather satellites will be. The noise will simply swamp the data, making what is collected useless. The article doesn't give a 'doomsday' timeframe, when we'll have no better ability to forecast the weather than they did in the 1800s, but that is what they are talking about."
Well, I am not sure how great we are at predicting the weather now.
A kid at my son's school collected and analyzied common RSS weather feeds for a science project.
He collected the data and used it to judge how accurate the weatherman's predictions were.
Within 5 degrees and 25% chance of rain, he gave them credit. They got credit 50ish percent of the time.
He then analyzied other ways of predicting the weather.
By just saying that the weather today will be the same as the weather yesterday, he got credit 50ish percent of the time.
I don't say this to belittle the weather people. I do this to say that the techniques we use now are not the greatest in the world. If we need those frequencies because they are the only ones that work, then maybe the gov't should buy them back. However, if those frequencies are used because that's the old school way of doing it, well, they aren't working at that great now.
Don't bother asking the FCC for help - they're too worried about someone saying fuck or showing their tits. Seriously tho, what sort of idiot would actually sell these frequencies if they knew what they were used for?
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Why would your car radar be useful if the signal it emits is attenuated by water vapour? Drive through some fog & you're in trouble.. ?
No Norm, those are your safety glasses; I'll wear my own thanks...
Question to those who might know this - assuming the ITU agrees to these restrictions, how would they enforce them? The radar frequency was presumably sold by a national agency (a la FCC) which is clearly making money off the sale and doesn't seem to care about the reasons. So how would the ITU go about forcing them to behave?
Our cars are more important than anything else. Everyone should know that by now, including weathermen who can't predict the weather anyway.
Take the cheese to sickbay, the doctor should see it as soon as possible - B'Elanna Torres, "Learning Curve"
Oh, wait, I think that was the 1980s. In the 1880s, we had that thing with a man with a brolly and a woman in a summer dress hanging from seaweed. You could tell the weather according to which one came out of the house. AFAICT, the reliability was much the same as today.
My uncle Jack sticking a wet finger in the air and saying "Arrh, it looks like a [fine|rough] day tomorrow - I think I need a wee dram!" was more fun though!
Sent from my ASR33 using ASCII
The FCC has the power to ban the sales and use of any device that would cause interference to these frequency bands. I've owned radio transceivers that were made obsolete and worthless by FCC decisions to reallocate spectrum to other uses. The FCC had no obligation to compensate me for the loss in value of the radio equipment or to offer me other spectrum to replace what was lost. If car radar units are a problem, the FCC can prohibit their sales and use.
Mea navis aericumbens anguillis abundat
Radar detectors, and most radio receivers, do transmit low-powered signals on the same or similar frequencies to those that they receive. It's called local oscillator leakage/radiation. It's especially common in consumer grade electronics equipment. If you look at the block diagram of a superheterodyne receiver, you will find one or more local oscillators that are used to mix down the incoming signals to fixed intermediate frequencies for filtering, amplification and demodulation. These local oscillators are often a source of radiation due to poor design and shielding. Radar detector detectors and TV detector vans take advantage of this by listening for local oscillator radiation.
Mea navis aericumbens anguillis abundat
Like this would never happen.
"It is a greater offense to steal men's labor, than their clothes"
The radar in question is for follow collision avoidance. You set cruise control, and this stuff makes sure that you are not cruise controlling yourself into the rear end of the car ahead of you.
-Rusty
You never know...
Ever been to LA...
You can drive in any direction for between 5 and 20 hours depending on day and traffic conditions, and never leave the monotonous suburban landscape. It's the results of unplanned, unconsidered, growth. From space it looks like the great god of suburban blight dropped it "Splat" from high altitude like some surreal cow patty.
What the hell (you might ask) has any of that got to do with this article. The answer is that the same kind of thinking (or kack there of), is behind the morass that is our use of the electromagnetic spectrum.
Empire building, despotism, political back-biting, greed and intrigue, technology working around the ideocy that is our regulatory system, and nobody asking whether the left hand knows what the right hand is doing... A Chinese Fire Drill would look like close order drill compared the slow motion Loony Tune that passes for what we've got.
Sanity might look like;
1. Determine that spectrum which serves to valuable or significant a purpose to avoid protecting, and declare that sacrosanct. Being able to track water vapor by the way is one of those sacrosanct uses.
2. Give up on that selling the spectrum for fun and profit idea... it was a bad joke then and it hasn't gotten better with time.
3. Put the millitary on a sane leash (they really don't need 50% of the workable spectrum.)
4. Promote the hell out of advanced mutispectrum technologies and count the money.
We really need to get a few folks in the FCC who haven't technological myopia, and have the cojones to push through an agenda based on growing use, and growing technology.
Genda Bendte
Spectrum allocation is a large, time-varying, multivariable optimization problem. This document is an outline of some of the service requests/requirements, and how they need to mesh with each other, present and future technology availability, and physical limitations (like attenuation due to water at 24 GHz). Note that this document is only U.S. interests; every other country has a similar list, and all have to be coordinated. It's like the guy who goes into a store with three lists: What he wants to buy, what he needs to buy, and what he can afford to buy. Compromise is the name of the game, and reasonable people will make reasonable tradeoffs differently.
The radar this article is discussing is a proposed future use of 24 GHz for collision-avoidance radar in passenger cars. 24 GHz is a popular frequency choice for short-range applications like this specifically because of the atmospheric attenuation. Note that the attenuation at 24 GHz, while higher than at other nearby frequencies, is still relatively low, only a few tenths of a dB per kilometer (although much higher in rain). This makes 24 GHz a good compromise for short-range devices on the Earth's surface, especially low-powered devices with very directional antennas pointed horizontally, away from satellites. (A better choice from this standpoint would be the oxygen absorption band at 60 GHz, and there is indeed another radar band there.)
Meterologists are merely expressing their concern over how their measurements will be corrupted if millions of car radars are in operation, and their cumulative power is enough to be detected by their sensors. My personal opinion, however, is that 24 GHz is too low of a frequency to make a market-successful car radar; the antennas are too big. I think 60 or 77 GHz is a better bet; if so, that would preserve 24 GHz for water vapor measurements.
In general, though, the interests of meterologists and others performing microwave sensing of the earth should be considered in the frequency allocation process; the publicity due to this article is one way of accomplishing this.
It's the same with BPL. Now it's more important to use the frequency spectrum for businesses, despite its critical importance for public services. We will see the consequences in some years; just wait for the coordination in case of a catastrophe failing due to HF pollution, or to miss the prediction of an important storm due to polluted data.
It seems that nowadays there is a sort of inherent "right" to turn anything into business, completely ignoring the impact to the public.
Ok, water vapor sensing is exactly what I did for my master's thesis. I'm going to keep it brief though.
Water vapor has an absorption line centered at 22.235 GHz while liquid water's absorption increases with frequency^1.95. Vapor sensing radiometers do not generally measure at 22.235 GHz because the peak of the absorption line curve is extremely sensitive to pressure. There are points to either side where the curve is insensitive to changes in pressure allowing measurement throughout the entire atmosphere without having to know the pressure profile. That is why the scientists in the article want to keep the 23.6 to 24.0 GHz band for their measurments.
My radiometer measured the emission spectrum at 21.6, 22.235, and 31.6 GHz. 21.6 and 31.6 GHz were the measurements of vapor and liquid water, respectively. 31.6 GHz is a window between the 22.235 GHz vapor line and the group of oxygen lines around 60 GHz. This makes liquid the strongest contributor to the noise temperature at that frequency. The 22.235 GHz was to experiment with. By using 22.235 and 21.6 I tried to see if I could get reasonably similar results even though both frequencies were more sensitive to vapor than liquid. Two close frequencies are measureable using one antenna thereby making the radiometer less expensive and available for more widespread use. I showed that the measurement could be made, but a lot more data needed to be taken to refine the data processing. Enough information was there in the measurements, but there were factors I couldn't account for in the time I had. Hopefully in time, radiometers could become a much more common piece of weather sensing equipment. You can get a lot more data on vapor with a radiometer than you can with a weather balloon, but radiometers are currently expensive and therefore limited in usability. Water vapor is the single biggest driving factor in the weather, we NEED to be able to measure it. Cheaper radiometers would let us get more data and improve weather modeling.