As for no contribution, of course you know I'm referring to the specific topic at hand, which had moved on from the original thread as these things always do.
The idea that we should all bow at the knees of noggin because he is all-knowing and is never even slightly not completely right about anything (the initial comment was an aside in the first place) is something I'm sure noggin himself will find quite amusing....
Last edited by A former member on 4 March 2004 3:27pm
are they not able to have one single cable coming from the dish and then have the LNB thing behined the TV??
FYI, the LNB is the box on the end of the arm of the dish that the cable connects to; it's the thing which makes the dish a receiving antenna and not just a rather stupid looking piece of metal. The purposes of the dish is to reflect the signal from the satellite and focus it into a narrow (and consequently stronger) beam aimed at the LNB - basically just act like a mirror.
So no, you certainly can't put it behind the TV
Also FYI, LNB stands for 'Low noise block-downconverter', so called because it downconverts the extremely high frequency signals it receives (tens of Ghz) down into lower frequencies (thousands of Mhz) which are able to travel along the cable and be picked up by the receiver's tuner, the block part means that it downconverts the whole frequency range at once, and the low noise part is in there because it aims to do it without introducing very much noise on the signal (I think modern LNBs are down to about 0.2dB now aren't they?)
EDIT: Since I'm after something to do, I've knocked up a little diagram in paint which basically shows how the signal gets from the satellite into the receiver and the basic operation of the dish. Yes I know it's not perfect but you get the idea:
http://www.rp-networkservices.com/tvforum/uploads/satellite_copy2.jpg
Last edited by cwathen on 4 March 2004 3:50pm - 4 times in total
are they not able to have one single cable coming from the dish and then have the LNB thing behined the TV??
FYI, the LNB is the box on the end of the arm of the dish that the cable connects to; it's the thing which makes the dish a receiving antenna and not just a rather stupid looking piece of metal. The purposes of the dish is to reflect the signal from the satellite and focus it into a narrow (and consequently stronger) beam aimed at the LNB - basically just act like a mirror.
So no, you certainly can't put it behind the TV
Also FYI, LNB stands for 'Low noise block-downconverter', so called because it downconverts the extremely high frequency signals it receives (tens of Ghz) down into lower frequencies (thousands of Mhz) which are able to travel along the cable and be picked up by the receiver's tuner, the block part means that it downconverts the whole frequency range at once, and the low noise part is in there because it aims to do it without introducing very much noise on the signal (I think modern LNBs are down to about 0.2dB now aren't they?)
EDIT: Since I'm after something to do, I've knocked up a little diagram in paint which basically shows how the signal gets from the satellite into the receiver and the basic operation of the dish. Yes I know it's not perfect but you get the idea:
http://www.rp-networkservices.com/tvforum/uploads/satellite_copy2.jpg
Ahhh........ now I understand! I'll shut up now
I have cable anyways so theres no dish on my house!
I hold my hands up - I confused the 1D and Universal issue. Apologies.
However the thrust of my argument was that with current LNB standards you would need 4 independent LNB outputs to guarantee the ability to tune all Astra 2/Eurobird transmissions rather than the 2 cwathen suggested.
If you were to have 4 independent outputs - H Low, H High, V Low, V High - you could feed as many tuners and receivers as you liked via a switching matrix fed by the four inputs, with an output for each tuner. AIUI this is how some community satellite distribution systems work - though there are other systems that use frequency transposition to carry all four feeds on a much wider bandwith distribution system (effectively carrying all four feeds spread out across a wider bandwith - about 4GHz?), with a reverse transposer locally installed for each receiver controlled by voltage and tone switching, making it look like a normal LNB to a receiver.
Noggin mate, it was an aside, and to be fair looking back it was nit-picking on my part anyway -- and the handbags episode was immature on both my and I Hate...'s part... so for my part I apologise.
Was just wondering, do you think it would be technically feasible to produce an LNB and tuner with an uprated bandwidth, making the 22KHz switch unnecessary? I'm guessing you'd need better quality cabling though, and if you were to use shotgun cable, it would be even harder to get working properly.
One other thing, if you were to use 4 signals, is there not the potential for signal degradation when an already potentially weak (minidish + shotgun cable + bad weather for example) signal is split by the tuner? Potentially you could have 4 or 5 tuners running off one outlet; would this not degrade the signal to the point where the whole thing would fall over?
Noggin mate, it was an aside, and to be fair looking back it was nit-picking on my part anyway -- and the handbags episode was immature on both my and I Hate...'s part... so for my part I apologise.
Why apologise? It's only the internet, it wasn't as if we were screaming at each other in the middle of the street!
Noggin mate, it was an aside, and to be fair looking back it was nit-picking on my part anyway -- and the handbags episode was immature on both my and I Hate...'s part... so for my part I apologise.
No worries - I wasn't at all offended - just a bit odd being discussed in my absence! (Surprised people think much about anything technical I post to be honest)
Quote:
Was just wondering, do you think it would be technically feasible to produce an LNB and tuner with an uprated bandwidth, making the 22KHz switch unnecessary? I'm guessing you'd need better quality cabling though, and if you were to use shotgun cable, it would be even harder to get working properly.
Yep - perfectly feasible. I mentioned something similar in my previous post. Some community satellite systems use a frequency transposer to take the output of an H LNB and a V LNB and shift one well above the other - so that a single IF can carry both H and V channels - with either a modified receiver or an "un-transposer" before the receiver controlled by the LNB voltage output of a standard box. This requires that the cabling can carry twice the bandwith of a standard LNB IF system I guess. I don't know for sure, but I think there are systems that incorporate this with a wider band H & V LNB output to avoid the need for tone-switching - I think you end up piping around 4GHz bandwith IF signals as a result.
The transposer system does have the advantage that the system is passive - the 4 LNBs routed into a switching matrix system requires a switch per receiver and independent feeds from the matrix to each receiver. Cheaper for small installations than a transposer - but nto for larger set-ups.
Quote:
One other thing, if you were to use 4 signals, is there not the potential for signal degradation when an already potentially weak (minidish + shotgun cable + bad weather for example) signal is split by the tuner? Potentially you could have 4 or 5 tuners running off one outlet; would this not degrade the signal to the point where the whole thing would fall over?
With up to 4 tuners you'd probably use 4 separate LNBs in one (a la Quad LNB) - so each would be fed independently via separate cables. I assume there is some loss compared to a single LNB - but as they are all in one designs I suspect this is not too significant.
Similarly if you integrated multiple tuners fed from a single LNB in a receiver I would expect the performance to still be pretty good compared to routing the outputs to tuners in different locations. I think the connectors and cabling are significant losses in most distribution at these frequency levels - rather than the actual tuner loss?
