Current US law allows people to receive and listen to un-encrypted radio transmissions, except for cellular telephone channels, as long as the reception is for personal use only and not to be used in the commission of a crime.
That means you can sit around listening to the cops all day long, as long as you don't say "Hey, I heard all the cops are at the donut shop on the north side, so I can go rob the southside bank". It also means you can't legally sit around at your taxi company office and listen to the competition's radio system and jump their calls.
Symbol rate is the speed at which the bytes are transferred. It's usually in Baud, so if you have ever played with a classical modem (14K4 for example, it means 14400 Baud) you should know something about it.
DVB Satellite signals are specified in Megasymbols/sec, not baud. A DVB carrier is specified by the a few parameters:
Center frequency (either in the actual downlink frequency from the satellite or in L-Band after the LNB) Symbol rate (In kilo or megasymbols/sec) Modulation (BPSK, QPSK, 16PSK, 32PSK) FEC rate (1/2, 3/4, 7/8)
Once you lock onto the stream, then you can dig out the various PIDs.
Channels are multiplexed into a transponder.
Not multiplexed onto a transponder, but multiplexed into a carrier. A transponder can have multiple carriers, each carrier can have mutliple channels (separated by PIDs). Transponders are just a chunk of raw spectum on the satellite, each usually either 36 or 72MHz wide.
Most satellites nowadays use Mpeg 2 encoding to compress the data.
Technically, it's not the "satellite" that encodes the signal. The satellite is just a "radio bent pipe" in space. The ground station is what encodes the signal, the satellite just retransmits what it gets. MPEG-2 is the prevalent digital compression mode, but more services are going to MPEG-4, especially for HD video and on DVB-S2.
Not trying to be pedantic, just making sure the right terms are used. Having been in the satellite industry for 10+ years now, those things annoy me just as much as someone saying "I've got 250GB of memory in my computer"
No, there is no ATSC over satellite. You have either analogue Baseband audio/video which can be either clear or encrypted with Videocipher.
For digital, almost everything over the US is DVB-S or S2, with the occasional Digicipher outlier. DVB is often encrypted using Irdeto or similar conditional access.
Both types of polarization are used, depending on the satellite owner's preference. Intelsat is almost strictly circular on their transcontinental links, while the majority (if not all) domestic US birds are linear polarization.
Not all LNBs can do active polarity switching. LNBs for fixed VSAT terminals and fixed recieivers have their polarity adjusted by manually turning the feedhorn.
It's not just the outsiders saying the hobby is dying. Go to any ham club and you can find the group (usually aged 60+) who think all this new fangled internet shit is killing the hobby and how echolink isn't really "ham radio". Then you'll find the other group who embrace change and want to put up echolink/IRLP/packet/D-Star nodes.
Then you have the smaller group that hates anything above 28Mhz and you're not cool unless you have antennas that have to be stretched between trees.
And it also works when every cell site and PSTN trunk is tied up because Bob is calling Alice to make sure that they're okay after the hurricane/explosion/terrorist act/peanut butter sandwich incident.
Don't. You know that the whole thing is going to boil down to "Video Game 2: The Search for More Money". Upper management will be pressing so hard to get the game out while the original is still fresh in everyone's mind that plot development & bug testing go right out the window.
It not just "bad" caps. My 42" Samsung TV died, not because of defective caps in the power supply, but because the caps were inappropriately rated. They were 10V-rated caps in a 15V circuit. It was just only a matter of time before they died.
And thankfully I found articles on the cap issues before I plunked down $999 for a new TV. $2 in caps, and 45 minutes of my time solved the issue.
Well, $2 in caps, $23 in shit I didn't really need to cover minimum orders, and $20 in "overnight" shipping all because jASSper, TX was a shithole of a town and the local Ratshack doesn't carry anything but TV antennas and Verizon phones.
I know several couples who have only one debit card between them. Mostly they explain it by saying "That way John/Mary doesn't spend money I don't know about".
But then it usually turns out that John has the debit card and Mary is out writing checks and not telling John until John's debit card gets declined because they're $200 in the hole.
In my experience with satellite phone users, there's two types:
1) The guys who are going camping way out in the middle of Nowhere. They wont use their phone unless someone is dying. At that point, I don't think they care about per-minute costs. Usually, those folks have bought $50-100 prepaid airtime cards.
2) Businessmen who need to be in contact with home base no matter what. That includes oil/gas industries, or senior-level executives. The folks in accounting get the bill and the end user just knows to dial, press send, and then carry on.
Source: Me, having to provide sales & support services to Irridium and INMARSAT users.
Irridium has the advantage of being in low earth orbit versus Direcway's geosynchronous orbit. The path loss between a 250ish mile orbit and a 22,500 mile orbit is a hefty number of dB.
Assuming both systems At 2Ghz, it is 150dB at 250 miles and 190db at 22,500 miles. That 40db difference either has to be made up in raw transmit power at both ends or by using a 5.3m dish antenna.
The other issue is this: The direcway uplink bands are on frequencies shared with other uplinks on other satellites. Interference isn't a problem because each customer uplink dish is precisely aimed at the satellite and the antenna's beamwidth is such that there is no interference to adjacent satellites. Imagine the insanity of one person on the satphone to his stock broker, pacing back and forth, his uplink beam spattering all over the sky.
The links just won't close. I don't have the exact numbers I'd need to do a link budget, but the Direcway links are engineered for a Ku link with a.9m dish on the ground and a 3-4m dish on the spacecraft, with the ground transmitting at 2-4 watts. The TerreStar satellite has an 18m dish on the satellite. That's a crapload more gain. TerreStar also uses a 2Ghz link which is also virtually unaffected by weather.
Also keep in mind that generating sufficient output power at Ku frequencies is extremely inefficient. A Direcway 4W BUC amplifier draws about 50 watts out of its power supply. I doubt your average cell phone's battery can tolerate that.
It's not just a "Can I build it?" problem. In the US, you have to be properly licensed to transmit. The micro/femtocells the carriers are releasing are covered under their FCC license & authorization. If you built an OpenBTS box and wanted to use it at home, you'd have to obtain an FCC license for the transmitter. You'd also have to coordinate frequency plans with the other carriers operating in your area.
Read about the fun the guys at Burning Man went through to set theirs up.
I wouldn't complain if the femtocell was just $50... Or if they took $5/month off my bill... Or if calls/data/whatever were discounted while using the femtocell...
I had Sprint's airave box for a while. It made for good coverage (there was a hill between the closest sprint tower and my house), but the fact that I paid extra per month just so I could have the box irked me. Then I elected to pay even more per month for the "completely unlimited airtime" option when placing calls through the airave box.
In your black-and-white world, I'm sure that things work that way.
In some cases, they do.
In your world, you shouldn't complain if somebody goes through your trash and digs up everything from bills to medicine prescriptions. You willingly discarded it so callously, so it is not private at all. You should have incinerated it.
Once it hits the curb for trash collection, it's fair game. Tons of legal precedents have been set for this. If I want to dispose of my accounting ledgers for my meth operation, I damn well better torch or shred them.
After all, you willingly set foot outside.
Yep. Just like not doing something stupid like logging into my bank account from the untrusted computer at the hotel lobby, I have no control of my surroundings and have no expectations of privacy. It is a jungle out there.
In the US, there are no laws against receving un-encrypted data or voice communications (other than maybe cellular, I don't know the exact laws for that). What's illegal is using the reception of those signals for personal/business gain or for assistance in commission of a crime.
Its not specifically "VOIP" that lets you do it. It's the fact that most telcos will just pass along the Calling Party Number handed to them on the ISDN setup message, as rightly they should. If I purchase a PRI from a telco to say, share between businesses in an office complex, and get assigned a block of 10 DIDs, when I place an outgoing call on the circuit, how does the telco know what CID to set for the business placing the call.
Now, granted, there is ANI, which is often set to the main "Bill-To Number" on your customer account, and that is used in the event of a call to 911. But you almost always have to have a direct SS7 connection to get or set the ANI. Very rarely will you find a an end user that has SS7 capability.
It is the responsibility of the circuit end user to ensure that their customers are not playing mickey mouse games with CID. As a former administrator of a very large Asterisk deployment, I laid out the dialplans and configurations so that if someone was trying to set their CID to something outside of our DID pool, the system would reject the call and play a message about not setting bogus CIDs.
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Current US law allows people to receive and listen to un-encrypted radio transmissions, except for cellular telephone channels, as long as the reception is for personal use only and not to be used in the commission of a crime.
That means you can sit around listening to the cops all day long, as long as you don't say "Hey, I heard all the cops are at the donut shop on the north side, so I can go rob the southside bank". It also means you can't legally sit around at your taxi company office and listen to the competition's radio system and jump their calls.
Symbol rate is the speed at which the bytes are transferred. It's usually in Baud, so if you have ever played with a classical modem (14K4 for example, it means 14400 Baud) you should know something about it.
DVB Satellite signals are specified in Megasymbols/sec, not baud. A DVB carrier is specified by the a few parameters:
Center frequency (either in the actual downlink frequency from the satellite or in L-Band after the LNB)
Symbol rate (In kilo or megasymbols/sec)
Modulation (BPSK, QPSK, 16PSK, 32PSK)
FEC rate (1/2, 3/4, 7/8)
Once you lock onto the stream, then you can dig out the various PIDs.
Channels are multiplexed into a transponder.
Not multiplexed onto a transponder, but multiplexed into a carrier. A transponder can have multiple carriers, each carrier can have mutliple channels (separated by PIDs). Transponders are just a chunk of raw spectum on the satellite, each usually either 36 or 72MHz wide.
Most satellites nowadays use Mpeg 2 encoding to compress the data.
Technically, it's not the "satellite" that encodes the signal. The satellite is just a "radio bent pipe" in space. The ground station is what encodes the signal, the satellite just retransmits what it gets. MPEG-2 is the prevalent digital compression mode, but more services are going to MPEG-4, especially for HD video and on DVB-S2.
Not trying to be pedantic, just making sure the right terms are used. Having been in the satellite industry for 10+ years now, those things annoy me just as much as someone saying "I've got 250GB of memory in my computer"
No, there is no ATSC over satellite. You have either analogue Baseband audio/video which can be either clear or encrypted with Videocipher.
For digital, almost everything over the US is DVB-S or S2, with the occasional Digicipher outlier. DVB is often encrypted using Irdeto or similar conditional access.
Both types of polarization are used, depending on the satellite owner's preference. Intelsat is almost strictly circular on their transcontinental links, while the majority (if not all) domestic US birds are linear polarization.
Not all LNBs can do active polarity switching. LNBs for fixed VSAT terminals and fixed recieivers have their polarity adjusted by manually turning the feedhorn.
It's not just the outsiders saying the hobby is dying. Go to any ham club and you can find the group (usually aged 60+) who think all this new fangled internet shit is killing the hobby and how echolink isn't really "ham radio". Then you'll find the other group who embrace change and want to put up echolink/IRLP/packet/D-Star nodes.
Then you have the smaller group that hates anything above 28Mhz and you're not cool unless you have antennas that have to be stretched between trees.
And it also works when every cell site and PSTN trunk is tied up because Bob is calling Alice to make sure that they're okay after the hurricane/explosion/terrorist act/peanut butter sandwich incident.
And if the meter designer was worth a crap, they'd implement some sort of multicast (with error checking, of course) protocol for that.
Don't. You know that the whole thing is going to boil down to "Video Game 2: The Search for More Money". Upper management will be pressing so hard to get the game out while the original is still fresh in everyone's mind that plot development & bug testing go right out the window.
You have to think in Russian. Do you think you can do that?
And this is why my cats all stay inside.
I put my PC into a wooden case so the bits would properly resonate before being sent to the speakers.
It not just "bad" caps. My 42" Samsung TV died, not because of defective caps in the power supply, but because the caps were inappropriately rated. They were 10V-rated caps in a 15V circuit. It was just only a matter of time before they died.
And thankfully I found articles on the cap issues before I plunked down $999 for a new TV. $2 in caps, and 45 minutes of my time solved the issue.
Well, $2 in caps, $23 in shit I didn't really need to cover minimum orders, and $20 in "overnight" shipping all because jASSper, TX was a shithole of a town and the local Ratshack doesn't carry anything but TV antennas and Verizon phones.
Imagine if everyone attending the basketball game at the Georgia Dome in March 2008 had gotten a text message of "EF2 tornado coming!".
It wasn't pandemonium there because the storm came & went before anyone knew WTF was going on.
So, please, shut your face. And don't bring up that shitty movie.
It has a redeeming quality. Zooey Deschanel. In the shower.
I know several couples who have only one debit card between them. Mostly they explain it by saying "That way John/Mary doesn't spend money I don't know about".
But then it usually turns out that John has the debit card and Mary is out writing checks and not telling John until John's debit card gets declined because they're $200 in the hole.
Not true. I've run many voip calls across geosync links, and despite the lag time, conversations can flow quite nicely.
Going through two geosync links, now that just gets ugly.
In my experience with satellite phone users, there's two types:
1) The guys who are going camping way out in the middle of Nowhere. They wont use their phone unless someone is dying. At that point, I don't think they care about per-minute costs. Usually, those folks have bought $50-100 prepaid airtime cards.
2) Businessmen who need to be in contact with home base no matter what. That includes oil/gas industries, or senior-level executives. The folks in accounting get the bill and the end user just knows to dial, press send, and then carry on.
Source: Me, having to provide sales & support services to Irridium and INMARSAT users.
Irridium has the advantage of being in low earth orbit versus Direcway's geosynchronous orbit. The path loss between a 250ish mile orbit and a 22,500 mile orbit is a hefty number of dB.
Assuming both systems At 2Ghz, it is 150dB at 250 miles and 190db at 22,500 miles. That 40db difference either has to be made up in raw transmit power at both ends or by using a 5.3m dish antenna.
The other issue is this: The direcway uplink bands are on frequencies shared with other uplinks on other satellites. Interference isn't a problem because each customer uplink dish is precisely aimed at the satellite and the antenna's beamwidth is such that there is no interference to adjacent satellites. Imagine the insanity of one person on the satphone to his stock broker, pacing back and forth, his uplink beam spattering all over the sky.
The links just won't close. I don't have the exact numbers I'd need to do a link budget, but the Direcway links are engineered for a Ku link with a .9m dish on the ground and a 3-4m dish on the spacecraft, with the ground transmitting at 2-4 watts. The TerreStar satellite has an 18m dish on the satellite. That's a crapload more gain. TerreStar also uses a 2Ghz link which is also virtually unaffected by weather.
Also keep in mind that generating sufficient output power at Ku frequencies is extremely inefficient. A Direcway 4W BUC amplifier draws about 50 watts out of its power supply. I doubt your average cell phone's battery can tolerate that.
It's not just a "Can I build it?" problem. In the US, you have to be properly licensed to transmit. The micro/femtocells the carriers are releasing are covered under their FCC license & authorization. If you built an OpenBTS box and wanted to use it at home, you'd have to obtain an FCC license for the transmitter. You'd also have to coordinate frequency plans with the other carriers operating in your area.
Read about the fun the guys at Burning Man went through to set theirs up.
http://openbts.sourceforge.net/FieldTest/
I wouldn't complain if the femtocell was just $50... Or if they took $5/month off my bill... Or if calls/data/whatever were discounted while using the femtocell...
I had Sprint's airave box for a while. It made for good coverage (there was a hill between the closest sprint tower and my house), but the fact that I paid extra per month just so I could have the box irked me. Then I elected to pay even more per month for the "completely unlimited airtime" option when placing calls through the airave box.
I won't make that mistake again.
In your black-and-white world, I'm sure that things work that way.
In some cases, they do.
In your world, you shouldn't complain if somebody goes through your trash and digs up everything from bills to medicine prescriptions. You willingly discarded it so callously, so it is not private at all. You should have incinerated it.
Once it hits the curb for trash collection, it's fair game. Tons of legal precedents have been set for this. If I want to dispose of my accounting ledgers for my meth operation, I damn well better torch or shred them.
After all, you willingly set foot outside.
Yep. Just like not doing something stupid like logging into my bank account from the untrusted computer at the hotel lobby, I have no control of my surroundings and have no expectations of privacy. It is a jungle out there.
In the US, there are no laws against receving un-encrypted data or voice communications (other than maybe cellular, I don't know the exact laws for that). What's illegal is using the reception of those signals for personal/business gain or for assistance in commission of a crime.
Its not specifically "VOIP" that lets you do it. It's the fact that most telcos will just pass along the Calling Party Number handed to them on the ISDN setup message, as rightly they should. If I purchase a PRI from a telco to say, share between businesses in an office complex, and get assigned a block of 10 DIDs, when I place an outgoing call on the circuit, how does the telco know what CID to set for the business placing the call.
Now, granted, there is ANI, which is often set to the main "Bill-To Number" on your customer account, and that is used in the event of a call to 911. But you almost always have to have a direct SS7 connection to get or set the ANI. Very rarely will you find a an end user that has SS7 capability.
It is the responsibility of the circuit end user to ensure that their customers are not playing mickey mouse games with CID. As a former administrator of a very large Asterisk deployment, I laid out the dialplans and configurations so that if someone was trying to set their CID to something outside of our DID pool, the system would reject the call and play a message about not setting bogus CIDs.
That's what directional antennas are for.