Are sat dishes too small?
 

R. Mark Clayton wrote:

As most installations are "free" from $ky and any front of house / chimney
stack dishes are limited to 45cm

By what decree?

Bill

Are sat dishes too small?
 

On 05/06/2012 09:53, David Woolley wrote:
The satellite operators are constrained by the power from the photo
cells on the satellites, but choose the technical parameters of their
signals so as to get the maximum revenue (i.e. sell as many channels as
possible) consistent with producing an acceptable signal most of the
time. Increasing the bit rate on a multiplex means a higher signal to
noise ratio is required to receive it accurately.

Is that what they do? I assumed they kept the transponder symbol rate
the same, but squeezed more channels into it - with a resulting
continuous loss of quality as there are fewer bits per channel.

I suppose you could fiddle with the symbol rate or error correction, but
I'd be a little surprised.

Andy

Are sat dishes too small?
 

"Bill Wright" wrote in message
...
R. Mark Clayton wrote:

As most installations are "free" from $ky and any front of house /
chimney stack dishes are limited to 45cm

By what decree?

Bill

The Town and Country Planning (General Permitted Development) Order 1995
(H.1.a.i)


but amended by

The Town and Country Planning (General Permitted Development) Order 2005


http://www.communities.gov.uk/docume...drantennas.pdf

the latter allowed 60cm NOT 45cm - so well spotted.

Are sat dishes too small?
 

Andy Champ wrote:


Is that what they do? I assumed they kept the transponder symbol rate
the same, but squeezed more channels into it - with a resulting
continuous loss of quality as there are fewer bits per channel.


That is what they do to choose the rate in the first place. They can
then try and find the point that finds the best balance between number
of chargeable channels and what people are prepared to pay for a given
level of quality.

First choose the fastest bit rate that produces a usable signal for
enough of the time that the punters won't complain too much. This
maximises the number of channels at a given technical quality.

Then you can try reducing the quality until what people are prepared to
pay starts off dropping faster than the bit rate per channel.

Are sat dishes too small?
 

R. Mark Clayton wrote:
"Bill Wright" wrote in message
...
R. Mark Clayton wrote:

As most installations are "free" from $ky and any front of house /
chimney stack dishes are limited to 45cm
By what decree?

Bill

The Town and Country Planning (General Permitted Development) Order 1995
(H.1.a.i)


but amended by

The Town and Country Planning (General Permitted Development) Order 2005


http://www.communities.gov.uk/docume...drantennas.pdf

the latter allowed 60cm NOT 45cm - so well spotted.


and well known to dish installers, who often face florid-faced local
ladies who see the new dish as they walk their pet rats and declare,
"I'll send for the police!"

Bill

Are sat dishes too small?
 

Bill Wright wrote:
David Woolley wrote:

DSB dish sizes tend to be set by planning law. They are set based on
what is permissible without explicit planning permission.
The max size set by planning law significantly exceeds the range of
mini-dish sizes.

There are two limits; one for the first aerial and one for the second.
Are you referring to the smaller one. If so, I guess that there is a
combination of people self policing the visual impact of the dish and
also wanting to minimise the materials cost.

Are sat dishes too small?
 

On Tue, 05 Jun 2012 22:03:08 +0100, Bill Wright wrote:

R. Mark Clayton wrote:
"Bill Wright" wrote in message
...
R. Mark Clayton wrote:

As most installations are "free" from $ky and any front of house /
chimney stack dishes are limited to 45cm
By what decree?

Bill

The Town and Country Planning (General Permitted Development) Order 1995
(H.1.a.i)

but amended by

The Town and Country Planning (General Permitted Development) Order 2005

http://www.communities.gov.uk/docume...drantennas.pdf

the latter allowed 60cm NOT 45cm - so well spotted.

and well known to dish installers, who often face florid-faced local
ladies who see the new dish as they walk their pet rats and declare,
"I'll send for the police!"

Bill


y dish caused a lot of comment at first: I couldn't hear what was being
said, but the number of people who stopped/pointed/talked...!
It's not only 65cm (Only 5cm over permitted size) but pale cream and solid.
Fortunately it's about 20m back from the road and the house is set back from
the one next door, so the dish isn't visible for far along the road.

It used to suffer loss of signal in v. bad weather, then I realised that I
hadn't skewed the LNB. Since then there's been no problem at all.
--
Peter.
The gods will stay away
whilst religions hold sway

Are sat dishes too small?
 

"Bill Wright" wrote in message
...
R. Mark Clayton wrote:
"Bill Wright" wrote in message
...
R. Mark Clayton wrote:

As most installations are "free" from $ky and any front of house /
chimney stack dishes are limited to 45cm
By what decree?

Bill

The Town and Country Planning (General Permitted Development) Order 1995
(H.1.a.i)


but amended by

The Town and Country Planning (General Permitted Development) Order 2005


http://www.communities.gov.uk/docume...drantennas.pdf

the latter allowed 60cm NOT 45cm - so well spotted.
and well known to dish installers, who often face florid-faced local
ladies who see the new dish as they walk their pet rats and declare, "I'll
send for the police!"

Bill

In Scotland:

2 antennas maximum (fronting and non-fronting (these terms are not
specifically used in the Order))
1 antenna: up to 100cm and 35 litres cubic capacity.
Other antennas: up to 60cm and 35 litres cubic capacity.
Chimney-mounted antenna: up to 60cm and 35 litres cubic capacity

I love teh idea of a dish having cubic capacity.

Are sat dishes too small?
 

In article , Bill Wright
wrote:
Jeff Layman wrote:

I have always understood that the 45 cm Sky disk was the minimum size
that Sky could get away with for (usually?) reliable reception. When
I looked into getting Freesat a couple of years - or maybe more -
ago, the minimum size of disk available relatively cheaply, complete
with receiver, was 65 cm. Apart from having to move the dish because
of a tree growing too high, I've never had reception problems from
28.5° here in Sussex, no matter what the cloud cover.

We find it helpful to use larger dish sizes for communal systems where
there is a lot of amplification, because the increased s/n ratio (less
beamwidth means less sky noise)

Erm...

I'm puzzled by you saying a larger dish ("less beamwidth") means "less
sky noise". I can see that a larger dish will have a higher gain, so
should pick up more signal. But why do you say a larger dish will reduce
sky noise? I'd expect the improvement in CNR to be due to more signal,
not less sky noise.

Although I can see that reducing the dish overspill may reduce the noise
from what the feed sees around the rim of the dish (house, ground,
whatever). Are you assuming a larger dish will also give a changed
illumination factor?

Slainte,

Jim

--
Please use the address on the audiomisc page if you wish to email me.
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Armstrong Audio http://www.audiomisc.co.uk/Armstrong/armstrong.html
Audio Misc http://www.audiomisc.co.uk/index.html

Are sat dishes too small?
 

Jim Lesurf wrote:

I'm puzzled by you saying a larger dish ("less beamwidth") means "less
sky noise". I can see that a larger dish will have a higher gain, so
should pick up more signal. But why do you say a larger dish will reduce
sky noise? I'd expect the improvement in CNR to be due to more signal,
not less sky noise.

I'd agree with you. If there were no temperature variations, you would
expect the amount of noise to be independent of the dish diameter.

A smaller dish may see more warm buildings than a large one. Warm is
relative; the sky is very cold.