thc69 wrote Er...if BPL is up in said emergency, and ham fails, then why not just use the BPL connection?
BPL may be down in the disaster area but it may be up in another area, preventing that area from receiving the transmission.
Let's put this in computer terms:
You've got an 802.11g wireless access point in your house. It is using a specific set of frequencies to maintain your connection between the AP and your computer. Let's say that you are using channel 9 in the US, meaning that your AP is communicating on a small slice of spectrum surrounding 2.452GHz (2452MHz).
Now let's put a microwave oven in your house. Your microwave oven is set to generate energy at 2.450GHz (2450MHz). There is a magnetron inside the microwave designed to generate energy at that frequency. It most likely doesn't generate just 2450MHz waves but generates energy on frequencies that generate a narrow bell curve centered on 2450MHz.
Now let's say that your microwave oven is a little out of spec. The shielding is a little leaky and the magnetron is generating energy at a little higher frequency. Now your microwave is putting out energy at 2451MHz +/- 1MHz. That means that the generated energy stretches from 2450MHz to 2452MHz.
Your wireless access point actually uses 22MHz of spectrum, meaning that the signal stretches from 2441MHz to 2463MHz. But look! Your microwave is "transmitting" from 2450MHz to 2452MHz, right on top of the bandwidth used by your AP. Not only that, part of that energy is right on your center or carrier frequency, which is part of what makes this all work.
Now it's time to talk about noise. Imagine that you're trying to hold a conversation across a table in a crowded room. If you're in a quiet restaurant, you should be able to hear each other across the table easily. If you're in a diner with music playing, it because a little more difficult to hear because you've got the constant level of background music. If you're in a bar, it's a little more difficult to hear since the background noise is even louder. If you're in a dance club, it's going to be even more difficult. As the background noise becomes louder, you have to increase your speech volume to overcome the background noise.
The signal to noise ratio is the amount of received signal compared to the amount of noise in the environment. In the conversation scenario, it's how much louder your voice is than the other noise in the room. As the background noise increases, you have to increase your volume (power) to be heard over the noise.
The same thing happens with your wireless access point. There is a certain amount of radio noise in the environment. As long as the AP signal is a certain amount stronger than the noise, when measured at your computer's antenna, the computer can communicate with the AP. If the signal isn't stronger than the noise, the computer can't talk to the AP.
Now you decide to turn on the microwave. It starts generating additional energy (noise, as far as your computer and AP are concerned) right on the frequencies used to communicate. If the new noise level is higher than the signal level, you're offline. (I know of one installation where I can reproduce this exact scenario on command. Turn off the microwave and one computer can't talk until the microwave is turned off.)
The same thing happens with ham radio. If there is an emergency and BPL goes offline, I can receive fairly well because the noise level just dropped significantly. When I try to transmit (most likely at a reduced power level, since I'm running on emergency power), my signal has to be received by someone else. If that person is right next to a BPL source that is leaking lots of noise, he isn't going to be able to pick up my signal because the background noise masks the my signal.
thc69 wrote Damn the ham....
Let's look at potentially affected spectrum. Here are a couple of important links:
because a lot of the smaller services are based on the same software.
We did a fair amount of research in this area when deciding how to handle online backups for our customers. (In many cases, offices without an IT staff and tape backups are a bad mix.)
As it turns out, there are a few companies that offer their own backup services at varying levels of service (LiveVault, Connected, @Backup, etc.) and there are a few companies that sell online backup software, which allows you to buy the software and open your own business. One of the biggest is Remote Backup Systems, which a friend of mine used to start his backup business.
The basic system is something like this:
Send RBS some money
Install backup software on your server
Sign up some backup customers
Profit!
RBS even has a "Business Kit" (an extra $200-ish) which includes a business plan, web site, telephone scripts, service contracts, etc.
But when you allow a calculator, you are NOT testing their knowledge of the basic techniques. Multiplying 99x2314 means learning a more advanced technique with paper and pencil.
Although it was probably unintentional, this is a perfect example of the kind of problem that kids will never understand how to do quickly and easily if they don't learn the techniques and just rely on a calculator.
The answer is 229086, which should take all of about three seconds to calculate.
Teach a kid to use a calculator and he's going to punch it in and get the right answer, as long as he hits all of the right buttons.
Teach a kid long multiplication and he'll come up with something like this:
If he's learned enough math to see the calculation, he's going to figure it out like this: 2314 * 99 = 2314 * (100 - 1) = 231400 - 2314 = 229086. Suddenly the most complicated part of the problem is subtraction and you are much less likely to make an error.
#1 - Call from remote office. Server isn't working.
Office manager was cold, so she bought a 1500W electric space heater. She needed a place to plug it in and there just happened to be an empty outlet on the UPS that fed the server, which was conveniently located right across the hall from her office.
Plug in heater, heater kicks on, high current starts, battery backup melts down, and server goes into SSF mode (Sparks, Smoke, and Flames). RAID card burned out and the machine is pretty much toasted. Defintely a power issue.
That office needed a new server anyway.
#2 - Call from dentist's office. Computers won't connect to the network and they are getting weird errors. Drop by office to inspect. Reboot computers and everything seems to work fine.
Network swtich and router are located in a cabinet in the darkroom. There is a single cable that comes out of that cabinet from the UPS that feeds the network equipment. They are short on outlets in the darkroom.
When some of the employees need to use the film duplicator, their solution is to unplug this plug that doesn't seem to connect to anything important. (Never mind that beeping sound in the background!)
Network doesn't instantly fail, since the equipment stays on UPS for ten minutes. Since they don't have instant feedback to realize that what they're doing is bad, they never associate the bad action (pulling the plug) with the bad event (all computers quit working).
This is correct. My father ran a health club years ago and was a member of a local barter group. There eventually came a point where they had to deal with taxation issues, not just from an income standpoint but also from a sales tax standpoint. (Both of which are just an excuse for me to spend more time doing paperwork - bleech!)
My dad had some Excel files this week that he couldn't open. They were created in an older version and his version (2003) wouldn't open them. I ended up opening and saving them in my version (XP) and then sending them to him. Based on that experience, I'm going to respectfully disagree that this is "an anecdote perpetuated by people that don't like Microsoft."
There are compatibility issues between versions of Excel and I'm willing to prove it on demand, since I've still got the spreadsheets sitting on my desktop.
OpenOffice (1.9.74) did reasonably well opening the original files.
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thc69 wrote Er...if BPL is up in said emergency, and ham fails, then why not just use the BPL connection?
BPL may be down in the disaster area but it may be up in another area, preventing that area from receiving the transmission.
Let's put this in computer terms:
You've got an 802.11g wireless access point in your house. It is using a specific set of frequencies to maintain your connection between the AP and your computer. Let's say that you are using channel 9 in the US, meaning that your AP is communicating on a small slice of spectrum surrounding 2.452GHz (2452MHz).
Now let's put a microwave oven in your house. Your microwave oven is set to generate energy at 2.450GHz (2450MHz). There is a magnetron inside the microwave designed to generate energy at that frequency. It most likely doesn't generate just 2450MHz waves but generates energy on frequencies that generate a narrow bell curve centered on 2450MHz.
Now let's say that your microwave oven is a little out of spec. The shielding is a little leaky and the magnetron is generating energy at a little higher frequency. Now your microwave is putting out energy at 2451MHz +/- 1MHz. That means that the generated energy stretches from 2450MHz to 2452MHz.
Your wireless access point actually uses 22MHz of spectrum, meaning that the signal stretches from 2441MHz to 2463MHz. But look! Your microwave is "transmitting" from 2450MHz to 2452MHz, right on top of the bandwidth used by your AP. Not only that, part of that energy is right on your center or carrier frequency, which is part of what makes this all work.
Now it's time to talk about noise. Imagine that you're trying to hold a conversation across a table in a crowded room. If you're in a quiet restaurant, you should be able to hear each other across the table easily. If you're in a diner with music playing, it because a little more difficult to hear because you've got the constant level of background music. If you're in a bar, it's a little more difficult to hear since the background noise is even louder. If you're in a dance club, it's going to be even more difficult. As the background noise becomes louder, you have to increase your speech volume to overcome the background noise.
The signal to noise ratio is the amount of received signal compared to the amount of noise in the environment. In the conversation scenario, it's how much louder your voice is than the other noise in the room. As the background noise increases, you have to increase your volume (power) to be heard over the noise.
The same thing happens with your wireless access point. There is a certain amount of radio noise in the environment. As long as the AP signal is a certain amount stronger than the noise, when measured at your computer's antenna, the computer can communicate with the AP. If the signal isn't stronger than the noise, the computer can't talk to the AP.
Now you decide to turn on the microwave. It starts generating additional energy (noise, as far as your computer and AP are concerned) right on the frequencies used to communicate. If the new noise level is higher than the signal level, you're offline. (I know of one installation where I can reproduce this exact scenario on command. Turn off the microwave and one computer can't talk until the microwave is turned off.)
The same thing happens with ham radio. If there is an emergency and BPL goes offline, I can receive fairly well because the noise level just dropped significantly. When I try to transmit (most likely at a reduced power level, since I'm running on emergency power), my signal has to be received by someone else. If that person is right next to a BPL source that is leaking lots of noise, he isn't going to be able to pick up my signal because the background noise masks the my signal.
thc69 wrote Damn the ham....
Let's look at potentially affected spectrum. Here are a couple of important links:
because a lot of the smaller services are based on the same software.
We did a fair amount of research in this area when deciding how to handle online backups for our customers. (In many cases, offices without an IT staff and tape backups are a bad mix.)
As it turns out, there are a few companies that offer their own backup services at varying levels of service (LiveVault, Connected, @Backup, etc.) and there are a few companies that sell online backup software, which allows you to buy the software and open your own business. One of the biggest is Remote Backup Systems, which a friend of mine used to start his backup business.
The basic system is something like this:
RBS even has a "Business Kit" (an extra $200-ish) which includes a business plan, web site, telephone scripts, service contracts, etc.
Although it was probably unintentional, this is a perfect example of the kind of problem that kids will never understand how to do quickly and easily if they don't learn the techniques and just rely on a calculator.
The answer is 229086, which should take all of about three seconds to calculate.
Teach a kid to use a calculator and he's going to punch it in and get the right answer, as long as he hits all of the right buttons.
Teach a kid long multiplication and he'll come up with something like this:If he's learned enough math to see the calculation, he's going to figure it out like this: 2314 * 99 = 2314 * (100 - 1) = 231400 - 2314 = 229086. Suddenly the most complicated part of the problem is subtraction and you are much less likely to make an error.
Last week's issues:
#1 - Call from remote office. Server isn't working.
Office manager was cold, so she bought a 1500W electric space heater. She needed a place to plug it in and there just happened to be an empty outlet on the UPS that fed the server, which was conveniently located right across the hall from her office.
Plug in heater, heater kicks on, high current starts, battery backup melts down, and server goes into SSF mode (Sparks, Smoke, and Flames). RAID card burned out and the machine is pretty much toasted. Defintely a power issue.
That office needed a new server anyway.
#2 - Call from dentist's office. Computers won't connect to the network and they are getting weird errors. Drop by office to inspect. Reboot computers and everything seems to work fine.
Network swtich and router are located in a cabinet in the darkroom. There is a single cable that comes out of that cabinet from the UPS that feeds the network equipment. They are short on outlets in the darkroom.
When some of the employees need to use the film duplicator, their solution is to unplug this plug that doesn't seem to connect to anything important. (Never mind that beeping sound in the background!)
Network doesn't instantly fail, since the equipment stays on UPS for ten minutes. Since they don't have instant feedback to realize that what they're doing is bad, they never associate the bad action (pulling the plug) with the bad event (all computers quit working).
Power issues. Yep. Sheesh!
This is correct. My father ran a health club years ago and was a member of a local barter group. There eventually came a point where they had to deal with taxation issues, not just from an income standpoint but also from a sales tax standpoint. (Both of which are just an excuse for me to spend more time doing paperwork - bleech!)
My dad had some Excel files this week that he couldn't open. They were created in an older version and his version (2003) wouldn't open them. I ended up opening and saving them in my version (XP) and then sending them to him. Based on that experience, I'm going to respectfully disagree that this is "an anecdote perpetuated by people that don't like Microsoft."
There are compatibility issues between versions of Excel and I'm willing to prove it on demand, since I've still got the spreadsheets sitting on my desktop.
OpenOffice (1.9.74) did reasonably well opening the original files.