HD, 8PSK?

[simonhwsn]

Hi
I'm a newbie but I'm very enthusiast and I want to learn.
8PSK is a kind of... signal modulation? any satellite is capable to use it or just the newer ones, same question about HD channels and MPEG4 encoding...
thanks

 

[gadgtfreek]

Digiblur can point you in the right direction for knowledge on this. PM him.

 

[digiblur]

No need to PM...

Almost all of the satellites used for TV are simply bent pipes. They send out what they receive. So any signal thrown at them will come back down. Now if you use a high bandwidth signal without much FEC(forward error correction) then you'll need either/or a big dish or a strong signal. So on satellite slots like 77w where you have older satellites in spots they were not designed for you have to use a QPSK signal so you can have a sustainable decodable signal on the small residential dishes.

 

[Mr Tony]

8PSK can be used on any DBS satellite.

Its just the modulation.....some are QPSK and some are 8PSK

Phase-shift keying - Wikipedia, the free encyclopedia

8PSK allows them to get more channels on a TP. Dish uses a mixture of both QPSK and 8PSK on satellites

 

[jmccurrytech]

I guess there is such a thing as 8PSK Turbo Coded too??

 

[digiblur]

I guess there is such a thing as 8PSK Turbo Coded too??

That's the 8PSK dish uses.

 

[simonhwsn]

No need to PM...

Almost all of the satellites used for TV are simply bent pipes. They send out what they receive. So any signal thrown at them will come back down. Now if you use a high bandwidth signal without much FEC(forward error correction) then you'll need either/or a big dish or a strong signal. So on satellite slots like 77w where you have older satellites in spots they were not designed for you have to use a QPSK signal so you can have a sustainable decodable signal on the small residential dishes.

Let me put it in my words to see if I got it. In this kind of modulation, error-rate is too high that you need a strong signal wich old satellites are not designed to deal with, you could use 8PSK but the signal would be so weak that you would have to use a big dish, right?

8PSK can be used on any DBS satellite.

Its just the modulation.....some are QPSK and some are 8PSK

Phase-shift keying - Wikipedia, the free encyclopedia

8PSK allows them to get more channels on a TP. Dish uses a mixture of both QPSK and 8PSK on satellites

I'm assuming that's why old satellites are able to carry HD channels but would have to be on a QPSK signal wich it's not the best way to do so due bandwidth usage?

It's very hard for me to understand technical info in english but it's worth to try I appreciate your patience, thanks for sharing your knowledge.

 

[Mr Tony]

I'm assuming that's why old satellites are able to carry HD channels but would have to be on a QPSK signal wich it's not the best way to do so due bandwidth usage?

nope. Echo 3 at 61.5 is the oldest satellite in the Dish fleet (that still is being used) and the HD on there is all 8PSK. That satellite is what 10-12 years old I think

 

[digiblur]

nope. Echo 3 at 61.5 is the oldest satellite in the Dish fleet (that still is being used) and the HD on there is all 8PSK. That satellite is what 10-12 years old I think

I believe the Echo1/Echo2 combination at 148 had 8PSK on them.

 

[Mr Tony]

but they used QPSK only with those. I dont remember any 8PSK on 148

 

[simonhwsn]

nope. Echo 3 at 61.5 is the oldest satellite in the Dish fleet (that still is being used) and the HD on there is all 8PSK. That satellite is what 10-12 years old I think

Oh wait, then I misunderstood this part:

So on satellite slots like 77w where you have older satellites in spots they were not designed for...

Does it mean that satellites are designed for a specific orbital location? then birds at 77w can't use 8PSK because both were moved from another one and they aren't oriented properly?

 

[BuddyBoy]

8PSK and QPSK are methods of modulating an analog carrier with digital information in order to carry digital information on an analog signal. Dish went to 8PSK because you can carry 50% more digital payload, and they had sufficient signal to noise ratio to utilize it. 8PSK requires a higher S/N ratio than QPSK. Turbo codes are a type of forward error correction. You can think of this as a way of adding redundant information (extra bits) to a digital bitstream in order to recover the correct bits at the receiving end even when the signal has been corrupted somewhere in the middle. Hopefully you can see that the extra bits are added first (or actually, entirely new bits are generated), and then this new bitstream modulates the carrier.

 

[digiblur]

but they used QPSK only with those. I dont remember any 8PSK on 148

Now that I think of it, there was...I remember setting up a dish to shoot under a tree at my old house to check things out. google 8PSK 148w and you'll see several threads.

 

[mike123abc]

One might mention:

1. Old dish receivers do not have 8PSK decoders in them, so Dish uses QPSK for standard definition. All the HD receivers currently working support 8PSK, so Dish tends to use 8PSK for HD.

2. When they set up the Eastern Arc Dish decided it was going to be newer receivers only so they could do 8PSK on standard definition.

3. Scott recently posted the rumor that Dish is going to convert the Western Arc to 8PSK, so all the older receivers will need to be replaced.

Turbo coding is a different mathmatical formula used in the forward error correction (FEC). It is a better formula than the original one used. Dish 8PSK receiver chips can use either one, so Dish tends to use the Turbo mode to get the better results.

Using Turbo encoding one can actually use less power on the transponder because more errors can be corrected with a given amount of encoding.

 

[whatchel1]

So does anyone other than E* & BEV use the turbo coding on 8PSK? If so what receivers support the turbo coding? Kind of an FTA question but since it was brought up here I was just wondering if others are using the turbo coding. BTW not a hack question in case anyone thinks it is. Just wondering who else is using turbo and what receiver that are using.

 

[Ghpr13]

This might be a little OT but I've always wonder how those great big "screen-like" antennas I see in some yards get their signals from? Do they have to go through E* or D* too? I remember years back (about 30 or 35) when I lived in Chicago, my friend's Dad, who lived in Kentucky, had one, but I never knew if he had to pay a provider for the signal, or just purchase the receiver and programing was free. Also, I remember my friend telling me that when they watched certain programs like Johnny Carson & live sporting events, they seen what was going on while broadcast TV showed commercials...I never witness this myself, so I always wonder if this was true.
Can any "Old Pros" out there set me straight on this?
Ghpr13

 

[whatchel1]

OTA

This might be a little OT but I've always wonder how those great big "screen-like" antennas I see in some yards get their signals from? Do they have to go through E* or D* too? I remember years back (about 30 or 35) when I lived in Chicago, my friend's Dad, who lived in Kentucky, had one, but I never knew if he had to pay a provider for the signal, or just purchase the receiver and programing was free. Also, I remember my friend telling me that when they watched certain programs like Johnny Carson & live sporting events, they seen what was going on while broadcast TV showed commercials...I never witness this myself, so I always wonder if this was true.
Can any "Old Pros" out there set me straight on this?
Ghpr13

Are you asking about an Over the Air antenna?

 

[digiblur]

Some might be OTA antennas...free digital HD and SD signals. Or you might be talking about some older areas had ground to ground microwave TV signals. You were supposed to buy the receiver and subscription.

 

[navychop]

Some satellites are built for one specific location. The shape of the area where the signal hits the earth was fixed by the design and shape of the antenna on the satellite before it was launched. This is to minimize signal leakage onto other nations that may not want those signals. If you relocate such a satellite, you may need to make some tradeoffs.

Some satellites have antennas that can be "shaped" or re-aimed, mechanically or electronically, to change where their signal lands. For extra expense, of course. But then you have a satellite that can be more effectively used if moved to a new location.

 

[JimK2]

This might be a little OT but I've always wonder how those great big "screen-like" antennas I see in some yards get their signals from? Do they have to go through E* or D* too? I remember years back (about 30 or 35) when I lived in Chicago, my friend's Dad, who lived in Kentucky, had one, but I never knew if he had to pay a provider for the signal, or just purchase the receiver and programing was free. Also, I remember my friend telling me that when they watched certain programs like Johnny Carson & live sporting events, they seen what was going on while broadcast TV showed commercials...I never witness this myself, so I always wonder if this was true.
Can any "Old Pros" out there set me straight on this?
Ghpr13

Multichannel Multipoint Distribution Service were pretty popular in the late 1970s, though the early 1980's before DISH and other DBS providers. At that time in Silicon Valley, everybody was building "Coffee Can" antennas with a few transistors as local oscillator and mixer that downconvered the microwave received signal and feed your TV directly, at no cost, free HBO.

It got so bad that the MDS provider would drive around all the neighborhoods with a mobile spectrum analyzer and directional antenna, looking for the local oscillator frequency radiation, when they found a violator, they sent out cease and desist letter and demanded hundreds of dollars of payment or they would press charges.