While I'm not an antenna physicist, I've been a ham radio operator since 1958 and have built and used a LOT of antennae. I've discovered that there are trade-offs. I will be very interested to see how this pans out and hope that it is, indeed, a break-through.
Here are some of the reasons for my skepticism. An antenna that is smaller will inherently intercept less of the signal when used for reception. It's called capture area. When used for transmission there are usually reductions in efficiency due to increased losses in the components that are used to reduce the size. Other trade-offs often appear in the form of directionality, that is, the antenna radiates/receives better in some directions than others.
In the professor's blog, he mentioned that when he increased power to 100 watts at 21 MHz, the antenna melted. That means that energy, instead of being radiated, was converted to heat, AKA lost efficiency.
I have operated successfully with relatively small antennae and low power on the shortwave bands for a long time. My typical mobile setup is 4 watts at 14 MHZ to an antenna on the car trunk that's about 4 feet tall, a commercially made Huster brand with a 22 inch base section for those who are familiar with ham antennae. Using that setup, I, too, have made good contacts on all continents from the central US. As the old saying goes, you can make contacts with a wet noodle for an antenna if the band conditions are good.
Anyway, that's my take on it. I hope that I get a chance to try out one of his creations on the shortwave bands. It sounds like, if it works as billed, that it would be great for my mobile operation.
73 and "Do the Right Thing. It will gratify some people and astound the rest." - Mark Twain
I don't know what I expected, but it was basically just short clips of varying pink noise, (as opposed to white noise). I'm with the other commentators.. WTF does this have to do with an iPOD?? Into the bit bucket with the files and mod the article down..
"Do the Right Thing. It will gratify some people and astound the rest." - Mark Twain
The IE security issue dejure.. How about an MS update that simply shuts down all that extra junk by default instead of leaving it open for average Joe User? Make them turn it on if they absolutely need it for whatever reason. Duh!!
"Do the Right Thing. It will gratify some people and astound the rest." - Mark Twain
going to tank cause of all the folks on my node d/l-ing movies! Thanks a lot! It's bad enough with the Linux distros and pr0n d/l-er's. What happens when the broadband ISPs start limiting everyone to X Gigs of d/l per month? Go rent the friggin DVD. It's a lot quicker.
"Do the Right Thing. It will gratify some people and astound the rest." - Mark Twain
I've crossed the Atlantic in a non-powered boat..
on
Rowing the Pond Again
·
· Score: 1
but all that rowing sounds like a real bummer. I crossed from the Canary Islands to the Carribean in a 56 foot sail boat in 1969 and it was no picnic, even going "downhill" so to speak. Our crossing was in January and we had several days of up to 80 knot wind and 20+ foot waves. NO GPS or satellite phone then, but we had, in addition to celectial navigation, Loran A and I had my ham rig for communications - almost as good.
To the person who asked about food storage, I don't see that as much of a problem. The food for the six of us for the 28 days that it took us seemed to take up little room with a little planning, but we did have one shortage.. We ran out of tonic water after three weeks, but still had plenty of gin so we made do and it wasn't a total loss.
"Do the Right Thing. It will gratify some people and astound the rest." - Mark Twain
may be a dupe. It's not that hard to do a wipe of the HD.. I use a nice little utility on a floppy called Autoclave The only down-side is that it takes a while to do a high level over write of a large drive. If you're in a hurry, then take the sledge hammer approach...literally.
"Do the Right Thing. It will gratify some people and astound the rest." - Mark Twain
I have to use Windows here at the office because of some legacy software that will never be ported to Linux. I just had a lockup and had to reboot. My Linux boxes never do that to me. They're just cleaner and more straightforward.
I still have a Windows box at home because my grandkids have their games that they like to play when they come over...No, No, not "Grand Theft, Auto". They are 4 and 5 year old girls so it's Dora the Explorer and Barbie.
"Do the Right Thing. It will gratify some people and astound the rest." - Mark Twain
So I guess this is the rebuttal to the rebuttal of the first rebuttal..:-) Well done Andrew Tanenbaum!
Why doesn't KB just cut his losses and slink away before he's made a greater fool of, if that's possible. I suspect that his check has cleared the bank by now.
"Do the Right Thing. It will gratify some people and astound the rest." - Mark Twain
there's a high probability that it's still around somewhere that someone can find it if they look hard enough. It's a fact. If you want something private, don't type it into a digital device, don't write it down... You probably shouldn't even think it since the CIA is working on reading your thoughts, too. We're all screwed. Have a nice day.
"Do the Right Thing. It will gratify some people and astound the rest." - Mark Twain
but not through some random chat-roomish sort of way. I operate some discussion boards and have met some really nice people with whom I have something in common.
I was introduced to my wife through an e-mail from a mutual friend who I would not have know without the Internet. The Internet is a perfectly valid way to meet people, but not in a singles bar sort of way.
"Do the Right Thing. It will gratify some people and astound the rest." - Mark Twain
Does the FCC need to be redefined? Sure it does. Is it too intrusive? Sure it is, but we do need some competent agency to manage the limited resource known as our electromagnetic spectrum.
Do you want the CB operator down the street to have a 5 KW transmitter and operate on whatever frequency he wants? I very seriously doubt it. There's enough of that sort of thing going on now with the FCC in place. It was a problem back in the first two decades of the Twentieth Century let alone what would happen if there was no regulation now.
IMO most of the governmental agencies need a house cleaning, a return to their original limited purpose, but it has to be done in a logical fashion or you end up with a much worse mess than you had.
"Do the Right Thing. It will gratify some people and astound the rest." - Mark Twain
who are working to make our patent system a bit more fair and help with reducing the current abuses we are seeing. PubpatElectronic Frontier Foundation
"Do the Right Thing. It will gratify some people and astound the rest." - Mark Twain
when I got a patent on them for my corporate employer in the 70's using all discrete parts - no IC's. It's pretty easy today to build a small one with relatively few parts, but you have to look out for the noise that they produce. Here's a link to an application note for one that would work in this case: LM2575 ap note (warning, 26 page pdf) I still like linear regulators for a lot of applications unless efficiency is paramount.
"Do the Right Thing. It will gratify some people and astound the rest." - Mark Twain
it's a drop in the bucket compared to their $60 Billion in cash. It is just a simple "cost of doing business" for them. Not that I wouldn't be surprized if they rolled over on this without and appeal, but think about it.
"Do the Right Thing. It will gratify some people and astound the rest." - Mark Twain
The milliamp rating of the part bears no direct relationship to the need for heatsinking. The heatsink requirements are related to the amount of power that the regulator IC needs to dissipate to stay within rated operating temperature limits. The power dissipation is given by Pd=(Vin-Vout)*I. Where I is the current drawn through the regulator. For example, in this case being discussed, the voltage drop is roughly 5 volts across the IC and if the current was 1 amp, then the power being dissipated would be 5 watts. Given, from the data sheet, that the junction to ambient thermal resistance is 50 degrees C per watt, the junction temp rise above ambient for 5 watts would be 250 degrees C which is far in excess of the junction maximum operating temp of 125 degrees C. So in that example a heatsink, which reduces the junction to ambient thermal resistance, is clearly a necessity. See LM317 data sheet
Don't feel bad, though, it's a common misconception that has caused a lot of burned fingers. You are right that the heatsink can't hurt, even if not required, since lower temperatures are ralated to lower MTBF (Mean TIme Between Failures.)
"Do the Right Thing. It will gratify some people and astound the rest." - Mark Twain
I'm a college degreed Electrical Engineer with over 30 years of experience, including teaching electronics at the college level for three years. That regulator circuit looks quite familiar. As long as the heatsink is sufficient for the heat dissipation in the LM317, there should be no problem. Since this is powering only the wireless bridge, the current drain at 7 volts should be modest and it only needs to drop 5 volts across the regulator IC. The total power dissipation spread across both of the 1/2 watt resistors is only 85 milliwatts so no trouble there either.
If you are referring to the capacitor voltage ratings, the only requirement there is that the voltage rating of the cap be more than the voltage actually applied to it. For example a 35 volt cap is just fine with 6 volts across it. It could even be a 1,000 volt rated cap with no ill effects.
"Do the Right Thing. It will gratify some people and astound the rest." - Mark Twain
Isn't it better that as many folks as possible click on those ads so it costs M$ more money that ends up getting paid to slashdot? Maybe it doesn't work that way. Someone set me straight if it doesn't. On a commercial website that I run, we get paid to put up a banner (not for M$, admittedly) and then get paid an additional amount for each click-through.
It's immaterial to me since I subscribe to Slashdot and avoid the ads anyway. You subscribe, too, don't you?
"Do the Right Thing. It will gratify some people and astound the rest." - Mark Twain
believe anything that MS puts out in its ads? I think it's OK for MS to fund a pro-linux site that way so long as it does not affect their editorial policies.
"Do the Right Thing. It will gratify some people and astound the rest." - Mark Twain
Slashdot Mirror
"Would you like salt with that wound, Mr. McBride?"
Disclaimer: I'm not claiming that as an original quote on my part. Saw it on another forum and ROTFLMAO
"Do the Right Thing. It will gratify some people and astound the rest." - Mark Twain
While I'm not an antenna physicist, I've been a ham radio operator since 1958 and have built and used a LOT of antennae. I've discovered that there are trade-offs. I will be very interested to see how this pans out and hope that it is, indeed, a break-through.
Here are some of the reasons for my skepticism. An antenna that is smaller will inherently intercept less of the signal when used for reception. It's called capture area. When used for transmission there are usually reductions in efficiency due to increased losses in the components that are used to reduce the size. Other trade-offs often appear in the form of directionality, that is, the antenna radiates/receives better in some directions than others.
In the professor's blog, he mentioned that when he increased power to 100 watts at 21 MHz, the antenna melted. That means that energy, instead of being radiated, was converted to heat, AKA lost efficiency.
I have operated successfully with relatively small antennae and low power on the shortwave bands for a long time. My typical mobile setup is 4 watts at 14 MHZ to an antenna on the car trunk that's about 4 feet tall, a commercially made Huster brand with a 22 inch base section for those who are familiar with ham antennae. Using that setup, I, too, have made good contacts on all continents from the central US. As the old saying goes, you can make contacts with a wet noodle for an antenna if the band conditions are good.
Anyway, that's my take on it. I hope that I get a chance to try out one of his creations on the shortwave bands. It sounds like, if it works as billed, that it would be great for my mobile operation.
73 and "Do the Right Thing. It will gratify some people and astound the rest." - Mark Twain
for Pete's sake just don't broadcast it!! How simple is that. Duh!!
"Do the Right Thing. It will gratify some people and astound the rest." - Mark Twain
I don't know what I expected, but it was basically just short clips of varying pink noise, (as opposed to white noise). I'm with the other commentators.. WTF does this have to do with an iPOD?? Into the bit bucket with the files and mod the article down..
"Do the Right Thing. It will gratify some people and astound the rest." - Mark Twain
The IE security issue dejure.. How about an MS update that simply shuts down all that extra junk by default instead of leaving it open for average Joe User? Make them turn it on if they absolutely need it for whatever reason. Duh!!
"Do the Right Thing. It will gratify some people and astound the rest." - Mark Twain
Help the organizations that are fighting them Pubpat Electronic Frontier Foundation
"Do the Right Thing. It will gratify some people and astound the rest." - Mark Twain
going to tank cause of all the folks on my node d/l-ing movies! Thanks a lot! It's bad enough with the Linux distros and pr0n d/l-er's. What happens when the broadband ISPs start limiting everyone to X Gigs of d/l per month? Go rent the friggin DVD. It's a lot quicker.
"Do the Right Thing. It will gratify some people and astound the rest." - Mark Twain
but all that rowing sounds like a real bummer. I crossed from the Canary Islands to the Carribean in a 56 foot sail boat in 1969 and it was no picnic, even going "downhill" so to speak. Our crossing was in January and we had several days of up to 80 knot wind and 20+ foot waves. NO GPS or satellite phone then, but we had, in addition to celectial navigation, Loran A and I had my ham rig for communications - almost as good.
To the person who asked about food storage, I don't see that as much of a problem. The food for the six of us for the 28 days that it took us seemed to take up little room with a little planning, but we did have one shortage.. We ran out of tonic water after three weeks, but still had plenty of gin so we made do and it wasn't a total loss.
"Do the Right Thing. It will gratify some people and astound the rest." - Mark Twain
may be a dupe. It's not that hard to do a wipe of the HD.. I use a nice little utility on a floppy called Autoclave The only down-side is that it takes a while to do a high level over write of a large drive. If you're in a hurry, then take the sledge hammer approach...literally.
"Do the Right Thing. It will gratify some people and astound the rest." - Mark Twain
I have to use Windows here at the office because of some legacy software that will never be ported to Linux. I just had a lockup and had to reboot. My Linux boxes never do that to me. They're just cleaner and more straightforward.
I still have a Windows box at home because my grandkids have their games that they like to play when they come over...No, No, not "Grand Theft, Auto". They are 4 and 5 year old girls so it's Dora the Explorer and Barbie.
"Do the Right Thing. It will gratify some people and astound the rest." - Mark Twain
So I guess this is the rebuttal to the rebuttal of the first rebuttal.. :-) Well done Andrew Tanenbaum!
Why doesn't KB just cut his losses and slink away before he's made a greater fool of, if that's possible. I suspect that his check has cleared the bank by now.
"Do the Right Thing. It will gratify some people and astound the rest." - Mark Twain
there's a high probability that it's still around somewhere that someone can find it if they look hard enough. It's a fact. If you want something private, don't type it into a digital device, don't write it down... You probably shouldn't even think it since the CIA is working on reading your thoughts, too. We're all screwed. Have a nice day.
"Do the Right Thing. It will gratify some people and astound the rest." - Mark Twain
but not through some random chat-roomish sort of way. I operate some discussion boards and have met some really nice people with whom I have something in common.
I was introduced to my wife through an e-mail from a mutual friend who I would not have know without the Internet. The Internet is a perfectly valid way to meet people, but not in a singles bar sort of way.
"Do the Right Thing. It will gratify some people and astound the rest." - Mark Twain
Does the FCC need to be redefined? Sure it does. Is it too intrusive? Sure it is, but we do need some competent agency to manage the limited resource known as our electromagnetic spectrum.
Do you want the CB operator down the street to have a 5 KW transmitter and operate on whatever frequency he wants? I very seriously doubt it. There's enough of that sort of thing going on now with the FCC in place. It was a problem back in the first two decades of the Twentieth Century let alone what would happen if there was no regulation now.
IMO most of the governmental agencies need a house cleaning, a return to their original limited purpose, but it has to be done in a logical fashion or you end up with a much worse mess than you had.
"Do the Right Thing. It will gratify some people and astound the rest." - Mark Twain
who are working to make our patent system a bit more fair and help with reducing the current abuses we are seeing. Pubpat Electronic Frontier Foundation
"Do the Right Thing. It will gratify some people and astound the rest." - Mark Twain
when I got a patent on them for my corporate employer in the 70's using all discrete parts - no IC's. It's pretty easy today to build a small one with relatively few parts, but you have to look out for the noise that they produce. Here's a link to an application note for one that would work in this case: LM2575 ap note (warning, 26 page pdf) I still like linear regulators for a lot of applications unless efficiency is paramount.
"Do the Right Thing. It will gratify some people and astound the rest." - Mark Twain
it's a drop in the bucket compared to their $60 Billion in cash. It is just a simple "cost of doing business" for them. Not that I wouldn't be surprized if they rolled over on this without and appeal, but think about it.
"Do the Right Thing. It will gratify some people and astound the rest." - Mark Twain
The milliamp rating of the part bears no direct relationship to the need for heatsinking. The heatsink requirements are related to the amount of power that the regulator IC needs to dissipate to stay within rated operating temperature limits. The power dissipation is given by Pd=(Vin-Vout)*I. Where I is the current drawn through the regulator. For example, in this case being discussed, the voltage drop is roughly 5 volts across the IC and if the current was 1 amp, then the power being dissipated would be 5 watts. Given, from the data sheet, that the junction to ambient thermal resistance is 50 degrees C per watt, the junction temp rise above ambient for 5 watts would be 250 degrees C which is far in excess of the junction maximum operating temp of 125 degrees C. So in that example a heatsink, which reduces the junction to ambient thermal resistance, is clearly a necessity. See LM317 data sheet
Don't feel bad, though, it's a common misconception that has caused a lot of burned fingers. You are right that the heatsink can't hurt, even if not required, since lower temperatures are ralated to lower MTBF (Mean TIme Between Failures.)
"Do the Right Thing. It will gratify some people and astound the rest." - Mark Twain
I'm a college degreed Electrical Engineer with over 30 years of experience, including teaching electronics at the college level for three years. That regulator circuit looks quite familiar. As long as the heatsink is sufficient for the heat dissipation in the LM317, there should be no problem. Since this is powering only the wireless bridge, the current drain at 7 volts should be modest and it only needs to drop 5 volts across the regulator IC. The total power dissipation spread across both of the 1/2 watt resistors is only 85 milliwatts so no trouble there either.
If you are referring to the capacitor voltage ratings, the only requirement there is that the voltage rating of the cap be more than the voltage actually applied to it. For example a 35 volt cap is just fine with 6 volts across it. It could even be a 1,000 volt rated cap with no ill effects.
"Do the Right Thing. It will gratify some people and astound the rest." - Mark Twain
Isn't it better that as many folks as possible click on those ads so it costs M$ more money that ends up getting paid to slashdot? Maybe it doesn't work that way. Someone set me straight if it doesn't. On a commercial website that I run, we get paid to put up a banner (not for M$, admittedly) and then get paid an additional amount for each click-through.
It's immaterial to me since I subscribe to Slashdot and avoid the ads anyway. You subscribe, too, don't you?
"Do the Right Thing. It will gratify some people and astound the rest." - Mark Twain
routers look better all the time. At least you have some control over it....if you're a geek anyway.
Which ones of the consumer products are safe? I'm running a D-Link wireless right now.Yes the encryption is on.
"Do the Right Thing. It will gratify some people and astound the rest." - Mark Twain
so you don't have to see the ads.. You do subscribe, don't you?
"Do the Right Thing. It will gratify some people and astound the rest." - Mark Twain
believe anything that MS puts out in its ads? I think it's OK for MS to fund a pro-linux site that way so long as it does not affect their editorial policies.
"Do the Right Thing. It will gratify some people and astound the rest." - Mark Twain
Somebody quoted you over on the Yahoo SCOX board a little while ago. Way to go!
"Do the Right Thing. It will gratify some people and astound the rest." - Mark Twain
I guess that bad karma is pretty sticky. Even selling their preferred A-1 shares to Baystar didn't save them.
My Canadian friends are screaming bloody murder. I don't blame them.
"Do the Right Thing. It will gratify some people and astound the rest." - Mark Twain