The interference is in the Military A-Band, which covers 233-403 Mhz. This is used for shipboard radars, as well as radar at airfields. You don't have to use Ghz frequencies for radar, in fact the first WWII radars used were around 100 Mhz, IIRC.
My buddy has the exciter from a shipboard radar as his "Ham Radio" rig. This item generates 1000W CW and about 100 KW in pulse mode, which is what the radars use. It has 4 sections that each handle 1/4 of the band from 10 Khz to 1 GHz. That was then fed to a 10KW Power Amplifier and out. Just the exciter part sits in 3, 6-foot rack cabinets!
The average pulse power in the radars is around 100,000 Watts, and can be pumped up several orders of magnitude to "burn through" jamming if necessary (peak pulse power levels around 1 GWatt!) That field is being constantly swept around the area looking for threats using phased array panels, much faster than the old "Battlezone" radars, so the RF field is effectively everywhere.
Key fobs, RF remotes and Garage door openers are using the 330 Mhz junk band and are right in the middle of the Military A-Band. Doh! Unfortunately, they are also Part 15 users of the spectrum there, and are secondary users of those frequencies - they must not interfere and must accept any interference they experience. Double Doh!!
Macrovision wasn't an issue at all. Video-CD's, especially homemade ones, don't have any Macrovision protection on them. The DVD player doesn't switch on Macrovision on it's output unless it's told to do so by the DVD that's playing.
What I suspect happened to you was that you had a ground loop between your DVD player and VCR. Using the mixer device either isolated the grounds between the devices, or made them common (connected them together).
Reversing the polarity of the AC plug sometimes works for fixing this on some poorly designed equipment with bad internal ground isolation.
I have a PC in the audio and video paths between my DVD player and the stereo and TV, which had similar problems when I first hooked it up. I ran a cold-water pipe ground wire to the chassis of the DVD player, PC, and the stereo it's plugged into; and that fixed all the problems.
Isn't 7 HBO's and 5 Showtimes and 100 PPV's enough?
They don't seem have enough programming to fill the channels that are existing. Try surfing around 2:00 AM - Do we really need 200 more Infomercial channels?
I guess they could make do with a few more p0rn channels, though:)
What you should have learned is there's a big difference between good-natured jesting and hurtful sarcasm. If someone tells you you've crossed that line, you don't then proceed to spew yet some more of that very attitude, you apologize if you give a shit. Obviously, you don't.
What you also didn't learn is that as long as you continue to do this, as the previous poster AC said, all you're gonna get is FUCK YOU replies.
(And that's not just because you're on Slashdot. I'd tell you the same to your face in real life if you came on to me with an attitude like yours).
Maybe if you stated a legitimate question with a factual or even inquisitive tone, it might have gotten a serious response. However, your inquiry started out with mock sympathy for "Poor Jim", and the rest was dripping with sarcasm. What kind of answer did you really expect?
No, not all Hams are defensive, but those that are attacked by people with an "attitude" will defend themselves vociferiously.
If you _really_ want to learn something, lose the attitude, and you'll find most Hams actually enjoy passing on knowledge and information about their hobby to others!
I always clear the cache, then go and zip up the C:\Documents and Settings\{Username}\Application Data\Mozilla\Profiles\{Username}\{gibberish}.slt directory before upgrading just in case of disaster (at least on a Win2K/XP system). That backs up and saves all your bookmarks, cookies, mail and news, settings, etc.
Oh, yeah, by the way...
on
Field Day 2004
·
· Score: 2, Interesting
Pardon me replying to myself, but I just thought of a good P.S. to the parent post - I forgot the best part, that IRLP is a Linux-based application!! It runs under a stripped down version of Red Hat Linux. EchoLink is Windows-based freeware, AFAIK.
Re:why ham radio isn't popular
on
Field Day 2004
·
· Score: 1
You hit it on the head there, my friend. This is excactly what Field Day is all about. Test deployment of emergency equipment to simulate what would happen in a disaster situation. People go to remote areas all over the country (world?) and try to race to see how many contacts they can make in a 24 hour period.
Re:Going the way of the dinosaurs
on
Field Day 2004
·
· Score: 4, Interesting
There is some recent salvation of Ham radio through the internet itself, believe it or not!
There are 2 new (relatively) systems called IRLP and another called EchoLink. These use the internet to link Ham repeater sites all over the world, using streaming audio (like "RealAudio") between stations.
There are nearly 1000 nodes in IRLP, my repeater uses that protocol, and I'm not sure but EchoLink probably has a similar number of nodes as well.
This is helping to unite Ham radio interests with those related to the internet. This is also providing new Hams, most of which are Technician class and have no "HF" or long-distance communications privileges, a means to talk outside of their local repeater area for a change.
Previously, operating on Field Day or going over to an "Elmer's" house and having him let you work the low bands was the only DX (long distance) exposure most new Hams would ever get. These new internet linking systems are helping to make that experince more readily available. Before the internet became popular, talking to someone in a strange and foreign land was a rare and exciting experience.
A much better analogy would have been to refer to the digital vocoder in cellular phones. They take a phonemic audio sample and find the nearest match, then replace it with a compression token that represents that bit of speech.
That achieves compression effectively by recreating a high bandwith audio stream from a low bitrate stream of tokens.
A thought I had years ago is:
3-D imaging via raytracing can be thought of as one of the most aggressive forms of compression, in that you represent a fastastically complex high-bitrate stream (i.e. The World, or at least the 3-D scene in question) with a very small (usually under 1K) stream of "tokens" (the raytracer's command repertoire). That "compresses" billions of voxels of 3-D space into a tiny scene descrption stream, and vice-versa during "decompression".
Heh, my fave from there is where Homer is sitting on the couch, and they have an annoying animated Joe Millionaire banner in front of Homer's face, which he notices, breaks off a piece of and eats!
"Mmmmm... Promo...."
When I was a kid I went to a movie with my family while on vacation in Key West, (this is about 1970 or so) where I first saw ads in a movie theater before the show. They were mostly crappy ads from local businesses, but I thought to myself (at my wise age of 8 or so) "Jesus Christ - this is worse than television, thank God they don't do this at home". Well, it took many years but it caught on everywhere, finally. Phooey. I agree with you 100% - Ads are the "payment" we make to watch shit for free on commercial TV - we paid real hard earned $$ to watch a movie, not more goddamn ads!
Meanwhile, just the opposite is occuring with them cramming super-annoying advertising banners and flying, crawling, and yes, even whooshing logos into the program material.
Some of these take up the bottom 1/4 of the screen, and often cover a significant amount of the action or program. Spike, TNT, and TVLand are some of the worst offenders in this area.
And don't get me started on the credits. They now cram them into the upper 1/8th of the screen while they use the opportunity to spew spam at you for the duration using the other 7/8ths of the screen. I still don't know who any of the voice actors in "Tripping the Rift" are thanks to that annoying practice.
Is this fucked up or what? The program is full of ads and the ads now contain "programs". Sheesh.
Actually, it's the collapse of a LARGE amount of matter and/or energy that causes them, we think. The supermassive ones that appeared just after the big bang weren't collapsed stars (yet), just huge blobs of matter that didn't quite form a galaxy correctly. So I sit corrected - But I agree anything is possible - see my reply to the post above yours...
Anything is possible, but I prefer to err on the side of causality - things don't just appear - they either moved there or evolved there from somewhere or something else.
But as I said, anything is possible including the fact that maybe black holes shift dimensionally or something and could "pop up" at random where nothing existed previously, but it existed _somewhere_ before that, I would think.
But that then begs the question, and this is taking it to the extreme, where did the matter and/or energy that seeded the big bang come from? Did it just "appear"? If we ever answer that one, then the black hole thing should be trivial...
As far as we know, black holes result from the collapse of a star. They don't just "appear" for no reason. The new ones discovered were obscured by their accretion disks and the torus of gas and matter surrounding them.
That's like saying what if dead bodies suddenly started appearing everywhere - without there having been live people first. Corpses don't just "appear" out of nowhere, they have to be made:)
I sympathize with you. One of my best friends lives out in the country in Michigan on the edge of a business "corridor" (expressway with good cell coverage) and his house is about 1/10th mile beyond the coverage they provide. He's frustrated as well, the signal takes a dive into a black hole as he rounds the corner into his driveway.
His situation is like yours, where a passive repeater just won't provide the extra coverage distance or local area coverage extension you need. Good luck getting the cell people to erect another tower... There may not be much you can do.
Wow. You need to use the shift key once in a while so I know when to take a breath;)
In your instance you specify a system with 12dB of gain, overall (give or take a dB).
You are right about the aperture of RX - whatever falls on the RX antenna will be repeated with 12dB of gain, so the few microwatts that hit the stick will be thus amplified. This is where a directional antenna helps to concentrate the energy on the recieve element, as well as provides real signal gain when functioning as a transmit elemnt.
There may be a small excitation loss, but as you observed, it should be negligible.
Interference loss from the original signal will depend on the phase relationship of the antenna in the target area with that of the distant source. It might be helpful to move the target (inside) antenna about within a 1/4 wave (at 800 Mhz that's about 3-4 inches) area incrementally to see if it helps or hinders phase cancellation. Also the main signal is so attenuated that's why we're doing this in the first place!
This stuff I know from experience. I didn't read it anywhere, so I really can't point you to a good resource - all the people that taught me are dead.
However, I would suggest a Google search for "passive repeater" for starters.
"This only works if your cell phone is not a CDMA phone (which works at a frequency range of 1850-1990 MHz)."
That was all he said. I believe his reference was just to the frequency involved and that 800 Mhz mobile antennas would not work on CDMA phones in the 1850-1990 Mhz band.
RF in is RF out in this case. Any fancy modulation scheme applied to the carrier, such as frequency hopping (FDMA), or spread-sepectrum modulation via psuedorandom polynomials (CDMA), or simple muxing (TDMA) will not affect the passive repeater in any way, and will simply be repeated through.
It's conceiveable that the local CDMA phone may have some sort of cancellation interferece from the mixing of incoming and outgoing RF signals in the co-ax, but the whole point of spread-spectrum is that everyone is using all the band, just not the same particular part at exactly the same time; it's designed to endure through such collisions and interferences.
(BTW I'm a Ham and used to work as a professional RF design engineer).
It will work if you use 1.8 GHz antennas! I don't know if they make mobile antennas for that band, but if they're available, they should work. Maybe some Wi-Fi antennas might work, but they're pretty far from the 2.4 GHz band.
The co-ax losses will be significantly higher at the higher frequencies, though.
Believe it or not, you can do this with a couple of mobile antennas and some coax cable. It's called a passive repeater, and it actually does work, but may not provide enough gain for your purposes (it has no gain at all beyond the inherent gain of the antennas you use).
Take one antenna and put it in your living room or where you want to do most of your calling, then put the other one outside, on the roof or in a window that gets good reception with the cell phone normally.
Hook them together with some 50 Ohm Co-ax, RG-58 will do nicely but not for more than about 50 feet. If you need more length get a lower-loss Co-ax like RG-213 or RG-8.
Then, go in to the area where you call from and try it. You might be surprised. A buddy of mine worked for Motorola in an RF lab, and he couldn't hear his local Ham Radio repeater, so he did exactly this in his lab (read: Faraday Cage) and hooked an antenna inside the lab to one on the roof and it worked! That was at 440 Mhz, but cellular should work fine at 880 Mhz as well.
I think one of the more famous cases was when Vanilla Ice stole^H^H^H^Hampled Queen/Bowie's "Under Pressure" for his hit (?) "Ice, Baby". He didn't get permission and got the shit sued out of him. He wound up settling out of court, and made everyone in the (at the time) new "sampling" style of music very aware that they were using bits of copyrighted works and had BETTER get permission!
There's a fascinating bio of this artist (?) on rotten.com: Here
Slashdot Mirror
The interference is in the Military A-Band, which covers 233-403 Mhz. This is used for shipboard radars, as well as radar at airfields. You don't have to use Ghz frequencies for radar, in fact the first WWII radars used were around 100 Mhz, IIRC.
My buddy has the exciter from a shipboard radar as his "Ham Radio" rig. This item generates 1000W CW and about 100 KW in pulse mode, which is what the radars use. It has 4 sections that each handle 1/4 of the band from 10 Khz to 1 GHz. That was then fed to a 10KW Power Amplifier and out. Just the exciter part sits in 3, 6-foot rack cabinets!
The average pulse power in the radars is around 100,000 Watts, and can be pumped up several orders of magnitude to "burn through" jamming if necessary (peak pulse power levels around 1 GWatt!) That field is being constantly swept around the area looking for threats using phased array panels, much faster than the old "Battlezone" radars, so the RF field is effectively everywhere.
Key fobs, RF remotes and Garage door openers are using the 330 Mhz junk band and are right in the middle of the Military A-Band. Doh! Unfortunately, they are also Part 15 users of the spectrum there, and are secondary users of those frequencies - they must not interfere and must accept any interference they experience. Double Doh!!
Macrovision wasn't an issue at all. Video-CD's, especially homemade ones, don't have any Macrovision protection on them. The DVD player doesn't switch on Macrovision on it's output unless it's told to do so by the DVD that's playing.
What I suspect happened to you was that you had a ground loop between your DVD player and VCR. Using the mixer device either isolated the grounds between the devices, or made them common (connected them together).
Reversing the polarity of the AC plug sometimes works for fixing this on some poorly designed equipment with bad internal ground isolation.
I have a PC in the audio and video paths between my DVD player and the stereo and TV, which had similar problems when I first hooked it up. I ran a cold-water pipe ground wire to the chassis of the DVD player, PC, and the stereo it's plugged into; and that fixed all the problems.
Isn't 7 HBO's and 5 Showtimes and 100 PPV's enough?
:)
They don't seem have enough programming to fill the channels that are existing. Try surfing around 2:00 AM - Do we really need 200 more Infomercial channels?
I guess they could make do with a few more p0rn channels, though
Mmmmmmmmm.... Duff Brand LSD... (Drool)...
You just don't get it, do you?
What you should have learned is there's a big difference between good-natured jesting and hurtful sarcasm. If someone tells you you've crossed that line, you don't then proceed to spew yet some more of that very attitude, you apologize if you give a shit. Obviously, you don't.
What you also didn't learn is that as long as you continue to do this, as the previous poster AC said, all you're gonna get is FUCK YOU replies.
(And that's not just because you're on Slashdot. I'd tell you the same to your face in real life if you came on to me with an attitude like yours).
Everyone knows Tinfoil Hats only protect the wearer against Trolls...
Maybe if you stated a legitimate question with a factual or even inquisitive tone, it might have gotten a serious response. However, your inquiry started out with mock sympathy for "Poor Jim", and the rest was dripping with sarcasm. What kind of answer did you really expect?
No, not all Hams are defensive, but those that are attacked by people with an "attitude" will defend themselves vociferiously.
If you _really_ want to learn something, lose the attitude, and you'll find most Hams actually enjoy passing on knowledge and information about their hobby to others!
I always clear the cache, then go and zip up the
C:\Documents and Settings\{Username}\Application Data\Mozilla\Profiles\{Username}\{gibberish}.slt
directory before upgrading just in case of disaster (at least on a Win2K/XP system). That backs up and saves all your bookmarks, cookies, mail and news, settings, etc.
Pardon me replying to myself, but I just thought of a good P.S. to the parent post - I forgot the best part, that IRLP is a Linux-based application!! It runs under a stripped down version of Red Hat Linux. EchoLink is Windows-based freeware, AFAIK.
True. Which is why Hams talk about Radio, mostly.
You hit it on the head there, my friend. This is excactly what Field Day is all about. Test deployment of emergency equipment to simulate what would happen in a disaster situation. People go to remote areas all over the country (world?) and try to race to see how many contacts they can make in a 24 hour period.
There is some recent salvation of Ham radio through the internet itself, believe it or not!
There are 2 new (relatively) systems called IRLP and another called EchoLink. These use the internet to link Ham repeater sites all over the world, using streaming audio (like "RealAudio") between stations.
There are nearly 1000 nodes in IRLP, my repeater uses that protocol, and I'm not sure but EchoLink probably has a similar number of nodes as well.
This is helping to unite Ham radio interests with those related to the internet. This is also providing new Hams, most of which are Technician class and have no "HF" or long-distance communications privileges, a means to talk outside of their local repeater area for a change.
Previously, operating on Field Day or going over to an "Elmer's" house and having him let you work the low bands was the only DX (long distance) exposure most new Hams would ever get. These new internet linking systems are helping to make that experince more readily available. Before the internet became popular, talking to someone in a strange and foreign land was a rare and exciting experience.
A much better analogy would have been to refer to the digital vocoder in cellular phones. They take a phonemic audio sample and find the nearest match, then replace it with a compression token that represents that bit of speech.
That achieves compression effectively by recreating a high bandwith audio stream from a low bitrate stream of tokens.
A thought I had years ago is:
3-D imaging via raytracing can be thought of as one of the most aggressive forms of compression, in that you represent a fastastically complex high-bitrate stream (i.e. The World, or at least the 3-D scene in question) with a very small (usually under 1K) stream of "tokens" (the raytracer's command repertoire). That "compresses" billions of voxels of 3-D space into a tiny scene descrption stream, and vice-versa during "decompression".
Heh, my fave from there is where Homer is sitting on the couch, and they have an annoying animated Joe Millionaire banner in front of Homer's face, which he notices, breaks off a piece of and eats!
"Mmmmm... Promo...."
When I was a kid I went to a movie with my family while on vacation in Key West, (this is about 1970 or so) where I first saw ads in a movie theater before the show. They were mostly crappy ads from local businesses, but I thought to myself (at my wise age of 8 or so) "Jesus Christ - this is worse than television, thank God they don't do this at home". Well, it took many years but it caught on everywhere, finally. Phooey. I agree with you 100% - Ads are the "payment" we make to watch shit for free on commercial TV - we paid real hard earned $$ to watch a movie, not more goddamn ads!
Meanwhile, just the opposite is occuring with them cramming super-annoying advertising banners and flying, crawling, and yes, even whooshing logos into the program material.
Some of these take up the bottom 1/4 of the screen, and often cover a significant amount of the action or program. Spike, TNT, and TVLand are some of the worst offenders in this area.
And don't get me started on the credits. They now cram them into the upper 1/8th of the screen while they use the opportunity to spew spam at you for the duration using the other 7/8ths of the screen.
I still don't know who any of the voice actors in "Tripping the Rift" are thanks to that annoying practice.
Is this fucked up or what? The program is full of ads and the ads now contain "programs". Sheesh.
AMD annnounced today the new line of Semprini proc...
(sounds of announcer being taken away...)
Those responsible for this announcement have been sacked.
Actually, it's the collapse of a LARGE amount of matter and/or energy that causes them, we think. The supermassive ones that appeared just after the big bang weren't collapsed stars (yet), just huge blobs of matter that didn't quite form a galaxy correctly. So I sit corrected - But I agree anything is possible - see my reply to the post above yours...
That's why I qualified it with AFAWK ;)
Anything is possible, but I prefer to err on the side of causality - things don't just appear - they either moved there or evolved there from somewhere or something else.
But as I said, anything is possible including the fact that maybe black holes shift dimensionally or something and could "pop up" at random where nothing existed previously, but it existed _somewhere_ before that, I would think.
But that then begs the question, and this is taking it to the extreme, where did the matter and/or energy that seeded the big bang come from? Did it just "appear"? If we ever answer that one, then the black hole thing should be trivial...
As far as we know, black holes result from the collapse of a star. They don't just "appear" for no reason. The new ones discovered were obscured by their accretion disks and the torus of gas and matter surrounding them.
:)
That's like saying what if dead bodies suddenly started appearing everywhere - without there having been live people first. Corpses don't just "appear" out of nowhere, they have to be made
I sympathize with you. One of my best friends lives out in the country in Michigan on the edge of a business "corridor" (expressway with good cell coverage) and his house is about 1/10th mile beyond the coverage they provide. He's frustrated as well, the signal takes a dive into a black hole as he rounds the corner into his driveway.
His situation is like yours, where a passive repeater just won't provide the extra coverage distance or local area coverage extension you need. Good luck getting the cell people to erect another tower... There may not be much you can do.
Wow. You need to use the shift key once in a while so I know when to take a breath ;)
In your instance you specify a system with 12dB of gain, overall (give or take a dB).
You are right about the aperture of RX - whatever falls on the RX antenna will be repeated with 12dB of gain, so the few microwatts that hit the stick will be thus amplified. This is where a directional antenna helps to concentrate the energy on the recieve element, as well as provides real signal gain when functioning as a transmit elemnt.
There may be a small excitation loss, but as you observed, it should be negligible.
Interference loss from the original signal will depend on the phase relationship of the antenna in the target area with that of the distant source. It might be helpful to move the target (inside) antenna about within a 1/4 wave (at 800 Mhz that's about 3-4 inches) area incrementally to see if it helps or hinders phase cancellation. Also the main signal is so attenuated that's why we're doing this in the first place!
This stuff I know from experience. I didn't read it anywhere, so I really can't point you to a good resource - all the people that taught me are dead.
However, I would suggest a Google search for "passive repeater" for starters.
Why wouldn't it?
Thus quoth the original poster:
"This only works if your cell phone is not a CDMA phone (which works at a frequency range of 1850-1990 MHz)."
That was all he said. I believe his reference was just to the frequency involved and that 800 Mhz mobile antennas would not work on CDMA phones in the 1850-1990 Mhz band.
RF in is RF out in this case. Any fancy modulation scheme applied to the carrier, such as frequency hopping (FDMA), or spread-sepectrum modulation via psuedorandom polynomials (CDMA), or simple muxing (TDMA) will not affect the passive repeater in any way, and will simply be repeated through.
It's conceiveable that the local CDMA phone may have some sort of cancellation interferece from the mixing of incoming and outgoing RF signals in the co-ax, but the whole point of spread-spectrum is that everyone is using all the band, just not the same particular part at exactly the same time; it's designed to endure through such collisions and interferences.
(BTW I'm a Ham and used to work as a professional RF design engineer).
It will work if you use 1.8 GHz antennas! I don't know if they make mobile antennas for that band, but if they're available, they should work. Maybe some Wi-Fi antennas might work, but they're pretty far from the 2.4 GHz band.
The co-ax losses will be significantly higher at the higher frequencies, though.
Believe it or not, you can do this with a couple of mobile antennas and some coax cable. It's called a passive repeater, and it actually does work, but may not provide enough gain for your purposes (it has no gain at all beyond the inherent gain of the antennas you use).
Take one antenna and put it in your living room or where you want to do most of your calling, then put the other one outside, on the roof or in a window that gets good reception with the cell phone normally.
Hook them together with some 50 Ohm Co-ax, RG-58 will do nicely but not for more than about 50 feet. If you need more length get a lower-loss Co-ax like RG-213 or RG-8.
Then, go in to the area where you call from and try it. You might be surprised. A buddy of mine worked for Motorola in an RF lab, and he couldn't hear his local Ham Radio repeater, so he did exactly this in his lab (read: Faraday Cage) and hooked an antenna inside the lab to one on the roof and it worked! That was at 440 Mhz, but cellular should work fine at 880 Mhz as well.
I think one of the more famous cases was when Vanilla Ice stole^H^H^H^Hampled Queen/Bowie's "Under Pressure" for his hit (?) "Ice, Baby". He didn't get permission and got the shit sued out of him. He wound up settling out of court, and made everyone in the (at the time) new "sampling" style of music very aware that they were using bits of copyrighted works and had BETTER get permission!
There's a fascinating bio of this artist (?) on rotten.com: Here