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Freesat PVRs - can I check my understanding of the technology



 
 
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  #11  
Old October 28th 18, 09:04 PM posted to uk.tech.digital-tv
Bill Wright[_3_]
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Default Freesat PVRs - can I check my understanding of the technology

On 28/10/2018 19:27, NY wrote:

LS8 2QN, towards the top (south) end of the road.

From other postings, it seems as if the people who do use aerials are
split between those who use Emley Moor and those who use Belmont, even
though the profile for Belmont shows obstructions for all the 60%
Fresnel zone and one half of the 100% Fresnel zone.

Even with an aerial 50 m high (being silly, for the hell of it!)
JavaJive recommends Bilsdale for fringe reception but not Belmont. But
people have aerials in that direction, so presumably it must work for
them :-)


Computer predictions are not reliable. Time and time again I've found
them to be wrong. The only way is to climb on the roof with an analyser,
and even that won't tell you about periodic variations like tree
screening and co-channel interference.

In a location like yours my thinking would be biased towards Emley Moor.
As long as the signal strength was adequate from Emley I'd use it. Too
much chance of CCI with Belmont. I'd only use Belmont if I was desperate.

Bill
  #12  
Old October 28th 18, 10:12 PM posted to uk.tech.digital-tv
Andy Burns[_12_]
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Posts: 735
Default Freesat PVRs - can I check my understanding of the technology

NY wrote:

You mean I'd need one tuner per recording (even if all the channels
being recorded are in the same high/low band and the same polarisation),
rather than (as for terrestrial) one tuner which produces a data stream
that is split into separate recordings from the same multiplex.


No, for a given frequency/polarisation/band combination (where the band
just shifts the frequency range) you get a transponder, each transponder
carries multiple streams just like a mux does on terrestrial.

  #13  
Old October 28th 18, 11:30 PM posted to uk.tech.digital-tv
Java Jive[_3_]
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Posts: 1,662
Default Freesat PVRs - can I check my understanding of the technology

On 28/10/2018 20:04, Bill Wright wrote:

On 28/10/2018 19:27, NY wrote:

LS8 2QN, towards the top (south) end of the road.

From other postings, it seems as if the people who do use aerials are
split between those who use Emley Moor and those who use Belmont, even
though the profile for Belmont shows obstructions for all the 60%
Fresnel zone and one half of the 100% Fresnel zone.

Even with an aerial 50 m high (being silly, for the hell of it!)
JavaJive recommends Bilsdale for fringe reception but not Belmont. But
people have aerials in that direction, so presumably it must work for
them :-)


Computer predictions are not reliable. Time and time again I've found
them to be wrong. The only way is to climb on the roof with an analyser,
and even that won't tell you about periodic variations like tree
screening and co-channel interference.


Quite. A computer prediction can only do so much - tell you if
there's a hill in the way that you can't see from the site, etc. I do
say in my site's help section that, particularly for marginal
situations, it's best to do what the OP has done here, ask for advice
from knowledgeable local experts.
  #16  
Old October 29th 18, 01:38 AM posted to uk.tech.digital-tv
Paul Ratcliffe
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Posts: 2,329
Default Freesat PVRs - can I check my understanding of the technology

On Sun, 28 Oct 2018 19:36:17 -0000, NY wrote:

Were amplifiers and cables of a distribution system (presumably designed for
terrestrial at 400-850 MHz) up to the job of also passing a usable level of
satellite signal at a much higher frequency (10-15 GHz)? Evidently they
were!


No they weren't. You need waveguide for such stuff.
Satellite is downconverted to 950-2150 MHz typically out of the LNB, but
no idea what 'cable' distributions systems actually do these days.
  #17  
Old October 29th 18, 03:36 AM posted to uk.tech.digital-tv
Bill Wright[_3_]
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Posts: 3,031
Default Freesat PVRs - can I check my understanding of the technology

On 28/10/2018 19:36, NY wrote:

The short-lived British Satellite Broadcasting was laughably
unambitious about the number of channels so used one band and one
polarisation. Thus the signal could be distributed to blocks of flats
by simply adding it to the terrestrial feed and adjusting the
equalisation.


Were amplifiers and cables of a distribution system (presumably designed
for terrestrial at 400-850 MHz) up to the job of also passing a usable
level of satellite signal at a much higher frequency (10-15 GHz)?
Evidently they were!


No, they weren't. Signal loss at 10GHz in ordinary coax would be
something like 4dB per metre. All domestic satellite downconverts Ku
band signals to 0.850Ghz to 2.6GHz (called 'satellite IF'). Even so a
lot of equalisation would be needed to make the top end work.

Where a system has been designed for VHF radio, UHF TV, and satellite IF
the difference in launch slope and equalisation is great.

Bill
  #18  
Old October 29th 18, 09:40 AM posted to uk.tech.digital-tv
Ian Jackson[_7_]
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Posts: 175
Default Freesat PVRs - can I check my understanding of the technology

In message , Brian Gaff
writes
Yes, where did all those Squarials go?
Brian


I have two in the loft.
--
Ian
 




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