All posts by Peter Smith
Below are all of Peter Smith's postings, with the most recent are at the bottom of the page.P
Whitehawk Hill (Brighton and Hove, England) Full Freeview transSaturday 24 September 2011 5:53PM
Brighton
Apologies for double posting but I think I put this query in an inappropriate place. This one seems more relevant:
I'd like some advice from anyone who understands the modulation techniques and error-correction provided by digital TV.
I'm trying to decide what we should do with the MATV system at Brighton Marina after the DSO next March. With the analogue signals we transpose frequencies (channels) so as not to get RF pickup on any badly shielded drop leads etc and this is normal practice. For the digital channels we currently transpose three of the muxes but not the other three (why? I don't know - it was introduced on a legacy system before I moved here).
My question is: with the high power digital transmitters, should we transpose frequencies to avoid any direct RF pickup clashing with the (slightly delayed) MATV data stream and clobbering the BER? Or is it completely unnecessary with digital transmissions?
The corollary of these questions poses another: does it do any harm to transpose channel frequencies for digital TV? If not, we might as well transpose all six since our head-end equipment is frequency agile. Can I assume that there is nothing RF-specific in the data streams?
I'd be very grateful for any informed opinion or advice.
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Mike Dimmick and Briantist: Thank you both for your helpful replies. I think we will transpose, then. I'll also avoid C41, C44 and C47 (Brighton Central) and C50, C55 and C61 (Ovingdean) since there may just be coverage but it still leaves plenty of channels once analogue has gone.
Thanks again.
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P
Whitehawk Hill (Brighton and Hove, England) Full Freeview transWednesday 21 March 2012 10:12AM
Brighton
As a public service to the 800 households at Brighton Marina, this is to advise the Freeview channels have been transposed as follows:
BBCA channel 23
D3+4 channel 32
SDN channel 26
ArqA channel 29
ArqB channel 42
BBCB channel 51 (not transposed)
Transposition to lower frequencies was necessary to compensate for dodgy and lossy legacy cabling around the site. Reception from Whitehawk is now very good.
All the advice on this site concerning the Freeview reset procedure is valid and should fix any problems but, in case of difficulty, Marina residents should call the Estates office.
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P
Five million London homes must 'full retune' when switchover enSaturday 14 April 2012 1:04PM
Brighton
Briantist: small typo on this pages that slightly confuses the meaning: "Those viewers will "Freeview HD" (or other so called D-Book 7) receivers" should read "Those viewers with "Freeview HD" (or other so called D-Book 7) receivers"
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The Americans also referred to PAL as "Pale And Lousy", but we both agreed that the French SECAM was an acronym for "Scarcely Ever Colour As Meant"
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It would be equally interesting to look at the progress of disk drive capacity over a similar period. The first one I came across an an electronics apprentice was the IBM 305 RAMAC in 1961. Although it's out of your time period, I mention it because it weighed over a ton and stored 5 Mbytes on 50 x 24" magnetic disks and cost around $160,000 which was a LOT of money in those days
Within your time frame, I was using the DEC RK05 in 1976. This used exchangeable 2.5 Mbyte cartridges and cost $7,900 plus installation. There was also a fixed disk version, the RK05F, which stored double - 5 Mbytes. Both had to be mounted in 19" racks so a full rack of fixed disks would store about 50 Mbytes
Now, 6 Tb drives are freely available, a million fold increase but storage density is even better. Housings are available that will hold 14 x 3.5" disks in a rack shelf so it's about 840 Tb per rack, i.e. about 18 million times the storage in a rack.
This is not quite such a ratio as has been achieved with RAM but bear in mind all these disk devices use moveable heads flying above a rotating disk in a mechanical unit.
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Friday 23 September 2011 4:46PM
Brighton
I'd like some advice from anyone who understands the modulation techniques and error-correction provided by digital TV.
I'm trying to decide what we should do with the MATV system at Brighton Marina after the DSO next March. With the analogue signals we transpose frequencies (channels) so as not to get RF pickup on any badly shielded drop leads etc and this is normal practice. For the digital channels we currently transpose three of the muxes but not the other three (why? I don't know - it was introduced on a legacy system before I moved here).
My question is: with the high power digital transmitters, should we transpose frequencies to avoid any direct RF pickup clashing with the (slightly delayed) MATV data stream and clobbering the BER? Or is it completely unnecessary with digital transmissions?
The corollary of these questions poses another: does it do any harm to transpose channel frequencies for digital TV? If not, we might as well transpose all six since our head-end equipment is frequency agile. Can I assume that there is nothing RF-specific in the data streams?
I'd be very grateful for any informed opinion or advice.