Comment The PITS (reward) (Score 4, Interesting) 224
Does anyone remember playing the game "The PITS" on CompuServe? Or, even better, know if thesource survived?
http://games.wwco.com/pits/
Comment Re:Self damning (Score 1) 360
Dan,
I agree with your basic conclusion: the heat one feels when using a cell phone or handheld transceiver is due to the fact that much of the energy being consumed isn't being converted into RF. It's hard to make a transmitter that converts more than 30-40% of the energy consumed into RF, and efficiencies as poor as 10% or so aren't unusual.
But I did want to make a gentle technical correction. Your message suggests that there's very little absorption in the 2M (144-148 MHz) band used by your HT; this is actually incorrect.
Heating from RF is can be quantified by the specific absorption rate (SAR) of the body being heated when exposed to RF. As the name suggests, it's the amount of RF that gets absorbed by tissue in the body (which results in heating). It's usually measured in watts per kilogram.
It actually takes LESS power at VHF frequencies (like 2 meters) to reach a given SAR than it does at UHF, microwave, or HF. It's a result of resonance effects as the wavelength approaches the size of the human body.
Take a look at the FCC's OET Bulletin 65, which specifies the power levels at which you have to undertake an RF safety review of your amateur station. These power levels are derived from the amount of energy at a given frequency required to achieve a specific SAR. Note that for VHF, just 50 watts is enough to trigger the requirement. At HF frequencies, the levels are often much higher (500 watts for the 40M band, for example). In the 13cm band (2.4 GHz), you need to be operating at 250 watts or above before the FCC feels you need to do a routine evaluation for RF safety.
Greg Lapin, N9GL, has written about this fairly extensively on the ARRL Web site if you (or anyone else) are interested in learning more.
Once again, I'm not challenging your conclusion that most of the heat from holding a phone or radio transmitter is simply waste heat. And I'm certainly not asserting that there's any danger in using a cell phone or HT. But I thought you might be interested to know that the body actually is heated MORE by a given power level in the VHF range than it is by the frequencies used by cell phones.
Phil
I agree with your basic conclusion: the heat one feels when using a cell phone or handheld transceiver is due to the fact that much of the energy being consumed isn't being converted into RF. It's hard to make a transmitter that converts more than 30-40% of the energy consumed into RF, and efficiencies as poor as 10% or so aren't unusual.
But I did want to make a gentle technical correction. Your message suggests that there's very little absorption in the 2M (144-148 MHz) band used by your HT; this is actually incorrect.
Heating from RF is can be quantified by the specific absorption rate (SAR) of the body being heated when exposed to RF. As the name suggests, it's the amount of RF that gets absorbed by tissue in the body (which results in heating). It's usually measured in watts per kilogram.
It actually takes LESS power at VHF frequencies (like 2 meters) to reach a given SAR than it does at UHF, microwave, or HF. It's a result of resonance effects as the wavelength approaches the size of the human body.
Take a look at the FCC's OET Bulletin 65, which specifies the power levels at which you have to undertake an RF safety review of your amateur station. These power levels are derived from the amount of energy at a given frequency required to achieve a specific SAR. Note that for VHF, just 50 watts is enough to trigger the requirement. At HF frequencies, the levels are often much higher (500 watts for the 40M band, for example). In the 13cm band (2.4 GHz), you need to be operating at 250 watts or above before the FCC feels you need to do a routine evaluation for RF safety.
Greg Lapin, N9GL, has written about this fairly extensively on the ARRL Web site if you (or anyone else) are interested in learning more.
Once again, I'm not challenging your conclusion that most of the heat from holding a phone or radio transmitter is simply waste heat. And I'm certainly not asserting that there's any danger in using a cell phone or HT. But I thought you might be interested to know that the body actually is heated MORE by a given power level in the VHF range than it is by the frequencies used by cell phones.
Phil
Comment Re:Compatibility (Score 2, Funny) 492
- If we're not coming up with something new and innovative we're stuck making outlook clones. People don't like writing software like that.
What are you talking about?? Writing clones of commercial software is the prime directive of open source! I'm going to go out on a limb and say that actually there are quite a lot of people who like nothing more than doing exactly that.
Feed Sling throws in Mac-friendly SlingPlayer (theregister.com)
Apple TV... not on your TV
Sling Media has released the Mac version of its SlingPlayer viewing application. It's only nine months or so behind schedule, but better late than never we say. More to the point, the UK version is available from day one.
Feed Dell Linux is go (theregister.com)
Ubuntu named as distro for desktops and laptops
Dell has finally chosen a Linux distribution to offer on its desktop and laptop machines.
Comment Say No To Leasing (Score 1) 157
I can see it now... you get the free computer, and it's burdened with EULAs that say hackers can't repurpose the device (remember CueCAT barcode readers), followed by software that monitors what you do, floods you with ads, and collects marketing information about you.
No thanks.
When I slap down money for a hardware and software, I want to be beholden to no one. Ever.
No thanks.
When I slap down money for a hardware and software, I want to be beholden to no one. Ever.
Comment Re:Here's why I won't use wireless (Score 1) 254
If they opened your window, somehow I think bandwidth and data would be the last thing they steal.
Probably before that would be the TV, the stereo, the computer, your microwave, maybe the food in the fridge, the couch if they had a big truck....
I doubt they would want the data in your house. They probably have their own p0rn.
Probably before that would be the TV, the stereo, the computer, your microwave, maybe the food in the fridge, the couch if they had a big truck....
I doubt they would want the data in your house. They probably have their own p0rn.
Slashdot Top Deals
You have a tendency to feel you are superior to most computers.
