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aus+uk / uk.tech.digital-tv / Re: Satellite Dishes & Calculations

SubjectAuthor
* Satellite Dishes & CalculationsJava Jive
+* Re: Satellite Dishes & CalculationsMark Carver
|+* Re: Satellite Dishes & CalculationsThe Other John
||`- Re: Satellite Dishes & CalculationsTweed
|`* Re: Satellite Dishes & CalculationsJohn Hall
| `* Re: Satellite Dishes & CalculationsTweed
|  `* Re: Satellite Dishes & CalculationsDavid Woolley
|   +- Re: Satellite Dishes & CalculationsTweed
|   `- Re: Satellite Dishes & Calculationstony sayer
+- Re: Satellite Dishes & Calculationscharles
+* Re: Satellite Dishes & Calculationsalan_m
|`* Re: Satellite Dishes & CalculationsMark Carver
| +* Re: Satellite Dishes & CalculationsTweed
| |`* Re: Satellite Dishes & CalculationsMark Carver
| | `- Re: Satellite Dishes & CalculationsTweed
| +- Re: Satellite Dishes & Calculationsalan_m
| `* Re: Satellite Dishes & CalculationsJava Jive
|  `* Re: Satellite Dishes & CalculationsMikeS
|   +- Re: Satellite Dishes & CalculationsJava Jive
|   `* Re: Satellite Dishes & CalculationsNY
|    `* Re: Satellite Dishes & CalculationsDavid Woolley
|     `* Re: Satellite Dishes & CalculationsR. Mark Clayton
|      `- Re: Satellite Dishes & CalculationsAndy Burns
`* Re: Satellite Dishes & CalculationsR. Mark Clayton
 `* Re: Satellite Dishes & CalculationsR. Mark Clayton
  `* Re: Satellite Dishes & CalculationsJava Jive
   `* Re: Satellite Dishes & CalculationsR. Mark Clayton
    +- Re: Satellite Dishes & CalculationsDavid Woolley
    `* Re: Satellite Dishes & CalculationsJava Jive
     `- Re: Satellite Dishes & CalculationsR. Mark Clayton

Pages:12
Satellite Dishes & Calculations

<t50o1u$6d4$1@dont-email.me>

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From: jav...@evij.com.invalid (Java Jive)
Newsgroups: uk.tech.digital-tv
Subject: Satellite Dishes & Calculations
Date: Thu, 5 May 2022 15:47:21 +0100
Organization: A noiseless patient Spider
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 by: Java Jive - Thu, 5 May 2022 14:47 UTC

One for the pros here. According to this site ...

Satellite Dish Suggested Minimum Sizes
https://www.smartaerials.co.uk/blog/what-size-satellite-dish-do-i-need

"The further you’re away from the satellites in space the weaker the
received signal will be. As the satellites remain in geostationary orbit
around the equator the further in the UK north in the UK you are
installing your satellite dish the weaker the received signal will be,
meaning that satellites dishes installed in the north of England and
satellite usually require a larger dish that those using a comparable
service in the south of England."

I don't dispute the need of the larger dish, but I'm suspicious of the
reason given, not just because it is garble-worded, but more importantly
as follows ...

The radius of earth is about 6,371 km
The radius of the Clarke Belt is 42,164 km
The south coast of England is around 50 degrees N
The border between England & Scotland is around 55 degrees N

There is a nice little triangle solver here:
https://www.calculator.net/triangle-calculator.html

Putting the above into it gives us:

South Coast distance to Clarke Belt = 38,380 km
https://www.calculator.net/triangle-calculator.html?vc=&vx=6371&vy=&va=50&vz=42164&vb=&angleunits=d&x=62&y=34

Border distance to Clarke Belt = 38,862 km
https://www.calculator.net/triangle-calculator.html?vc=&vx=6371&vy=&va=55&vz=42164&vb=&angleunits=d&x=62&y=34

I accept that I haven't allowed for the sats being at 28E rather than
due south, but this is good enough to tell us that, for the two example
locations above, the order of magnitude of the difference in distance
from sat to dish is likely to be only around 1%, and, even after
applying the inverse square law, one would think that's not enough to
justify a substantially larger dish?

So what is the real reason for the greater size of dish needed?

--

Fake news kills!

I may be contacted via the contact address given on my website:
www.macfh.co.uk

Re: Satellite Dishes & Calculations

<jdia76FclaoU1@mid.individual.net>

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From: mark.car...@invalid.invalid (Mark Carver)
Newsgroups: uk.tech.digital-tv
Subject: Re: Satellite Dishes & Calculations
Date: Thu, 5 May 2022 16:53:10 +0100
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 by: Mark Carver - Thu, 5 May 2022 15:53 UTC

On 05/05/2022 15:47, Java Jive wrote:
>
>
> So what is the real reason for the greater size of dish needed?
>
Might it be because further north the 'footprint' of signal is more,
'diffuse' on the earth's surface  ?(Shine a torch onto a football to see
what I mean) Or I might just be talking bollocks  ?

Re: Satellite Dishes & Calculations

<t50t3v$g2b$1@dont-email.me>

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From: nom...@home.org (The Other John)
Newsgroups: uk.tech.digital-tv
Subject: Re: Satellite Dishes & Calculations
Date: Thu, 5 May 2022 16:13:52 -0000 (UTC)
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 by: The Other John - Thu, 5 May 2022 16:13 UTC

On Thu, 05 May 2022 16:53:10 +0100, Mark Carver wrote:

> Might it be because further north the 'footprint' of signal is more,
> 'diffuse' on the earth's surface  ?(Shine a torch onto a football to see
> what I mean) Or I might just be talking bollocks  ?

Doesn't the inverse square law have something to do with it?

--
TOJ.

Re: Satellite Dishes & Calculations

<59e3e6aa70charles@candehope.me.uk>

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Subject: Re: Satellite Dishes & Calculations
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Date: Thu, 05 May 2022 17:19:06 +0100
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 by: charles - Thu, 5 May 2022 16:19 UTC

In article <t50o1u$6d4$1@dont-email.me>,
Java Jive <java@evij.com.invalid> wrote:
> One for the pros here. According to this site ...

> Satellite Dish Suggested Minimum Sizes
> https://www.smartaerials.co.uk/blog/what-size-satellite-dish-do-i-need

> "The further you‘re away from the satellites in space the weaker the
> received signal will be. As the satellites remain in geostationary orbit
> around the equator the further in the UK north in the UK you are
> installing your satellite dish the weaker the received signal will be,
> meaning that satellites dishes installed in the north of England and
> satellite usually require a larger dish that those using a comparable
> service in the south of England."

> I don't dispute the need of the larger dish, but I'm suspicious of the
> reason given, not just because it is garble-worded, but more importantly
> as follows ...

> The radius of earth is about 6,371 km
> The radius of the Clarke Belt is 42,164 km
> The south coast of England is around 50 degrees N
> The border between England & Scotland is around 55 degrees N

> There is a nice little triangle solver here:
> https://www.calculator.net/triangle-calculator.html

> Putting the above into it gives us:

> South Coast distance to Clarke Belt = 38,380 km
> https://www.calculator.net/triangle-calculator.html?vc=&vx=6371&vy=&va=50&vz=42164&vb=&angleunits=d&x=62&y=34

> Border distance to Clarke Belt = 38,862 km
> https://www.calculator.net/triangle-calculator.html?vc=&vx=6371&vy=&va=55&vz=42164&vb=&angleunits=d&x=62&y=34

> I accept that I haven't allowed for the sats being at 28E rather than
> due south, but this is good enough to tell us that, for the two example
> locations above, the order of magnitude of the difference in distance
> from sat to dish is likely to be only around 1%, and, even after
> applying the inverse square law, one would think that's not enough to
> justify a substantially larger dish?

> So what is the real reason for the greater size of dish needed?

The transiting aerial on the sattelite is highly directional.

--
from KT24 in Surrey, England
"I'd rather die of exhaustion than die of boredom" Thomas Carlyle

Re: Satellite Dishes & Calculations

<jdiccgFd313U1@mid.individual.net>

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From: jun...@admac.myzen.co.uk (alan_m)
Newsgroups: uk.tech.digital-tv
Subject: Re: Satellite Dishes & Calculations
Date: Thu, 5 May 2022 17:30:06 +0100
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 by: alan_m - Thu, 5 May 2022 16:30 UTC

On 05/05/2022 15:47, Java Jive wrote:

>
> So what is the real reason for the greater size of dish needed?
>

I don't know the reason but perhaps

The path through the atmosphere is longer hence greater attenuation of
the signal ????

In the SE of England 28.2E the elevation is 25 degrees - in Scotland its
20 degrees. Possibly the same reason why a setting sun closer to the
horizon is red - the light travels further through the atmosphere.

--
mailto : news {at} admac {dot} myzen {dot} co {dot} uk

Re: Satellite Dishes & Calculations

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From: usenet.t...@gmail.com (Tweed)
Newsgroups: uk.tech.digital-tv
Subject: Re: Satellite Dishes & Calculations
Date: Thu, 5 May 2022 16:32:27 -0000 (UTC)
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 by: Tweed - Thu, 5 May 2022 16:32 UTC

The Other John <nomail@home.org> wrote:
> On Thu, 05 May 2022 16:53:10 +0100, Mark Carver wrote:
>
>> Might it be because further north the 'footprint' of signal is more,
>> 'diffuse' on the earth's surface  ?(Shine a torch onto a football to see
>> what I mean) Or I might just be talking bollocks  ?
>
> Doesn't the inverse square law have something to do with it?
>

Rain fade. The further north you go the lower the elevation angle therefore
more atmosphere in the signal path. Taken to its limit, up in the arctic
the sat dishes are almost pointing horizontal.

Re: Satellite Dishes & Calculations

<jdicueFd616U1@mid.individual.net>

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From: mark.car...@invalid.invalid (Mark Carver)
Newsgroups: uk.tech.digital-tv
Subject: Re: Satellite Dishes & Calculations
Date: Thu, 5 May 2022 17:39:42 +0100
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 by: Mark Carver - Thu, 5 May 2022 16:39 UTC

On 05/05/2022 17:30, alan_m wrote:
> On 05/05/2022 15:47, Java Jive wrote:
>
>>
>> So what is the real reason for the greater size of dish needed?
>>
>
> I don't know the reason but perhaps
>
>
> The path through the atmosphere is longer hence greater attenuation of
> the signal ????
>
> In the SE of England 28.2E the elevation is 25 degrees - in Scotland
> its 20 degrees.  Possibly the same reason why a setting sun closer to
> the horizon is red - the light travels further through the atmosphere.

Except the signal also similarly fades on all edges of the footprint
(which blows my theory out of the water too)

https://en.satexpat.com/coverage/east/28.2/

Re: Satellite Dishes & Calculations

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From: usenet.t...@gmail.com (Tweed)
Newsgroups: uk.tech.digital-tv
Subject: Re: Satellite Dishes & Calculations
Date: Thu, 5 May 2022 16:42:35 -0000 (UTC)
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 by: Tweed - Thu, 5 May 2022 16:42 UTC

Mark Carver <mark.carver@invalid.invalid> wrote:
> On 05/05/2022 17:30, alan_m wrote:
>> On 05/05/2022 15:47, Java Jive wrote:
>>
>>>
>>> So what is the real reason for the greater size of dish needed?
>>>
>>
>> I don't know the reason but perhaps
>>
>>
>> The path through the atmosphere is longer hence greater attenuation of
>> the signal ????
>>
>> In the SE of England 28.2E the elevation is 25 degrees - in Scotland
>> its 20 degrees.  Possibly the same reason why a setting sun closer to
>> the horizon is red - the light travels further through the atmosphere.
>
> Except the signal also similarly fades on all edges of the footprint
> (which blows my theory out of the water too)
>
> https://en.satexpat.com/coverage/east/28.2/
>
>

Isn’t that just the gain of the tx antenna falling off towards the edges of
its beam?

Re: Satellite Dishes & Calculations

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From: mark.car...@invalid.invalid (Mark Carver)
Newsgroups: uk.tech.digital-tv
Subject: Re: Satellite Dishes & Calculations
Date: Thu, 5 May 2022 17:43:46 +0100
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 by: Mark Carver - Thu, 5 May 2022 16:43 UTC

On 05/05/2022 17:42, Tweed wrote:
> Mark Carver <mark.carver@invalid.invalid> wrote:
>> On 05/05/2022 17:30, alan_m wrote:
>>> On 05/05/2022 15:47, Java Jive wrote:
>>>
>>>> So what is the real reason for the greater size of dish needed?
>>>>
>>> I don't know the reason but perhaps
>>>
>>>
>>> The path through the atmosphere is longer hence greater attenuation of
>>> the signal ????
>>>
>>> In the SE of England 28.2E the elevation is 25 degrees - in Scotland
>>> its 20 degrees.  Possibly the same reason why a setting sun closer to
>>> the horizon is red - the light travels further through the atmosphere.
>> Except the signal also similarly fades on all edges of the footprint
>> (which blows my theory out of the water too)
>>
>> https://en.satexpat.com/coverage/east/28.2/
>>
>>
> Isn’t that just the gain of the tx antenna falling off towards the edges of
> its beam?
>
Well yes, so I think that's the answer ?

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From: usenet.t...@gmail.com (Tweed)
Newsgroups: uk.tech.digital-tv
Subject: Re: Satellite Dishes & Calculations
Date: Thu, 5 May 2022 16:49:52 -0000 (UTC)
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 by: Tweed - Thu, 5 May 2022 16:49 UTC

Mark Carver <mark.carver@invalid.invalid> wrote:
> On 05/05/2022 17:42, Tweed wrote:
>> Mark Carver <mark.carver@invalid.invalid> wrote:
>>> On 05/05/2022 17:30, alan_m wrote:
>>>> On 05/05/2022 15:47, Java Jive wrote:
>>>>
>>>>> So what is the real reason for the greater size of dish needed?
>>>>>
>>>> I don't know the reason but perhaps
>>>>
>>>>
>>>> The path through the atmosphere is longer hence greater attenuation of
>>>> the signal ????
>>>>
>>>> In the SE of England 28.2E the elevation is 25 degrees - in Scotland
>>>> its 20 degrees.  Possibly the same reason why a setting sun closer to
>>>> the horizon is red - the light travels further through the atmosphere.
>>> Except the signal also similarly fades on all edges of the footprint
>>> (which blows my theory out of the water too)
>>>
>>> https://en.satexpat.com/coverage/east/28.2/
>>>
>>>
>> Isn’t that just the gain of the tx antenna falling off towards the edges of
>> its beam?
>>
> Well yes, so I think that's the answer ?
>
Well yes if you deliberately tilt the beam downwards to restrict the
northerly coverage, but would you be doing that over your intended service
area? There aren’t many ex-pats north of Scotland. (Reykjavik gets
surprisingly good coverage from UK intended beams)

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From: jun...@admac.myzen.co.uk (alan_m)
Newsgroups: uk.tech.digital-tv
Subject: Re: Satellite Dishes & Calculations
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 by: alan_m - Thu, 5 May 2022 16:58 UTC

On 05/05/2022 17:39, Mark Carver wrote:
> On 05/05/2022 17:30, alan_m wrote:
>> On 05/05/2022 15:47, Java Jive wrote:
>>
>>>
>>> So what is the real reason for the greater size of dish needed?
>>>
>>
>> I don't know the reason but perhaps
>>
>>
>> The path through the atmosphere is longer hence greater attenuation of
>> the signal ????
>>
>> In the SE of England 28.2E the elevation is 25 degrees - in Scotland
>> its 20 degrees.  Possibly the same reason why a setting sun closer to
>> the horizon is red - the light travels further through the atmosphere.
>
> Except the signal also similarly fades on all edges of the footprint
> (which blows my theory out of the water too)
>
> https://en.satexpat.com/coverage/east/28.2/
>

Just go west from the South of England to the footprint limits of 28.2E
reception

Elevation 25 degrees in the SE England
Elevation 21 degrees in Killarney (far west of Ireland).

Going that far west gives the same elevation as going north to Scotland.

--
mailto : news {at} admac {dot} myzen {dot} co {dot} uk

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From: john_nos...@jhall.co.uk (John Hall)
Newsgroups: uk.tech.digital-tv
Subject: Re: Satellite Dishes & Calculations
Date: Thu, 5 May 2022 18:09:52 +0100
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 by: John Hall - Thu, 5 May 2022 17:09 UTC

In message <jdia76FclaoU1@mid.individual.net>, Mark Carver
<mark.carver@invalid.invalid> writes
>On 05/05/2022 15:47, Java Jive wrote:
>>
>>
>> So what is the real reason for the greater size of dish needed?
>>
>Might it be because further north the 'footprint' of signal is more,
>'diffuse' on the earth's surface  ?(Shine a torch onto a football to
>see what I mean) Or I might just be talking bollocks  ?

Wouldn't that be counteracted by tilting the dish at the optimum angle
so that the signal still impacts on it at 90 degrees? The suggestion
that it's due to a longer passage through the atmosphere causing more
attenuation seems more likely.
--
John Hall
"Home is heaven and orgies are vile,
But you *need* an orgy, once in a while."
Ogden Nash (1902-1971)

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From: usenet.t...@gmail.com (Tweed)
Newsgroups: uk.tech.digital-tv
Subject: Re: Satellite Dishes & Calculations
Date: Thu, 5 May 2022 17:22:21 -0000 (UTC)
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 by: Tweed - Thu, 5 May 2022 17:22 UTC

John Hall <john_nospam@jhall.co.uk> wrote:
> In message <jdia76FclaoU1@mid.individual.net>, Mark Carver
> <mark.carver@invalid.invalid> writes
>> On 05/05/2022 15:47, Java Jive wrote:
>>>
>>>
>>> So what is the real reason for the greater size of dish needed?
>>>
>> Might it be because further north the 'footprint' of signal is more,
>> 'diffuse' on the earth's surface  ?(Shine a torch onto a football to
>> see what I mean) Or I might just be talking bollocks  ?
>
> Wouldn't that be counteracted by tilting the dish at the optimum angle
> so that the signal still impacts on it at 90 degrees? The suggestion
> that it's due to a longer passage through the atmosphere causing more
> attenuation seems more likely.

At 10 GHz atmospheric attenuation is 0.02dB per km, propagating
horizontally at sea level.

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 by: Java Jive - Thu, 5 May 2022 20:09 UTC

Although I'm only replying to this one, I've read all the replies so
far; thanks for them all ...

On 05/05/2022 17:39, Mark Carver wrote:
>
> On 05/05/2022 17:30, alan_m wrote:
>>
>> On 05/05/2022 15:47, Java Jive wrote:
>>>
>>> So what is the real reason for the greater size of dish needed?
>>
>> I don't know the reason but perhaps the path through the atmosphere is
>> longer hence greater attenuation of the signal ????

Yes, I'd thought of that as well, and I think that's the most likely
explanation, see also below ...

>> In the SE of England 28.2E the elevation is 25 degrees - in Scotland
>> its 20 degrees.  Possibly the same reason why a setting sun closer to
>> the horizon is red - the light travels further through the atmosphere.

Yes.

> Except the signal also similarly fades on all edges of the footprint
> (which blows my theory out of the water too)
>
> https://en.satexpat.com/coverage/east/28.2/

I don't dispute that the signal fades towards the edge of coverage, but
if you look at the coverage map there, coverage is centred on the
British Isles as a whole, so if the need for a larger dish was due to
fading of the signal towards the edge of coverage, the border area
should be getting a stronger signal than the south coast of England, and
therefore a smaller dish should be needed in the borders, and a larger
one on the south coast, whereas reality is the other way round!

I think the argument about the amount of atmosphere the signal has to
travel through is the most convincing so far suggested.

--

Fake news kills!

I may be contacted via the contact address given on my website:
www.macfh.co.uk

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From: Mik...@fred.com (MikeS)
Newsgroups: uk.tech.digital-tv
Subject: Re: Satellite Dishes & Calculations
Date: Fri, 6 May 2022 09:55:13 +0100
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 by: MikeS - Fri, 6 May 2022 08:55 UTC

On 05/05/2022 21:09, Java Jive wrote:
> Although I'm only replying to this one, I've read all the replies so
> far; thanks for them all ...
>
> On 05/05/2022 17:39, Mark Carver wrote:
>>
>> On 05/05/2022 17:30, alan_m wrote:
>>>
>>> On 05/05/2022 15:47, Java Jive wrote:
>>>>
>>>> So what is the real reason for the greater size of dish needed?
>>>
>>> I don't know the reason but perhaps the path through the atmosphere is
>>> longer hence greater attenuation of the signal ????
>
> Yes, I'd thought of that as well, and I think that's the most likely
> explanation, see also below ...
>
>>> In the SE of England 28.2E the elevation is 25 degrees - in Scotland
>>> its 20 degrees.  Possibly the same reason why a setting sun closer to
>>> the horizon is red - the light travels further through the atmosphere.
>
> Yes.
>
>> Except the signal also similarly fades on all edges of the footprint
>> (which blows my theory out of the water too)
>>
>> https://en.satexpat.com/coverage/east/28.2/
>
> I don't dispute that the signal fades towards the edge of coverage, but
> if you look at the coverage map there, coverage is centred on the
> British Isles as a whole, so if the need for a larger dish was due to
> fading of the signal towards the edge of coverage, the border area
> should be getting a stronger signal than the south coast of England, and
> therefore a smaller dish should be needed in the borders, and a larger
> one on the south coast, whereas reality is the other way round!
>
> I think the argument about the amount of atmosphere the signal has to
> travel through is the most convincing so far suggested.
>
There should be sufficient information here
http://www.apsattv.com/techinfo/predicting-out-of-footprint-coverage.htm
to answer your question with facts rather than speculation.

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From: dav...@ex.djwhome.demon.invalid (David Woolley)
Newsgroups: uk.tech.digital-tv
Subject: Re: Satellite Dishes & Calculations
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 by: David Woolley - Fri, 6 May 2022 09:38 UTC

On 05/05/2022 18:22, Tweed wrote:
> At 10 GHz atmospheric attenuation is 0.02dB per km, propagating
> horizontally at sea level.

That's only in good weather. Rain causes a lot of attenuation. Whilst
I don't know exactly how much, uplink powers have to be controlled to
avoid overloading transponders when there is no rain, whilst providing
enough signal in rain.

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From: usenet.t...@gmail.com (Tweed)
Newsgroups: uk.tech.digital-tv
Subject: Re: Satellite Dishes & Calculations
Date: Fri, 6 May 2022 10:15:50 -0000 (UTC)
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 by: Tweed - Fri, 6 May 2022 10:15 UTC

David Woolley <david@ex.djwhome.demon.invalid> wrote:
> On 05/05/2022 18:22, Tweed wrote:
>> At 10 GHz atmospheric attenuation is 0.02dB per km, propagating
>> horizontally at sea level.
>
> That's only in good weather. Rain causes a lot of attenuation. Whilst
> I don't know exactly how much, uplink powers have to be controlled to
> avoid overloading transponders when there is no rain, whilst providing
> enough signal in rain.
>

Yes, correct. I had a look at rain fade attenuation last night and it’s
more of an art than a science. There’s at least half a dozen models for it.
Slant angle does play a part.

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 by: Java Jive - Fri, 6 May 2022 11:52 UTC

On 06/05/2022 09:55, MikeS wrote:
>
> On 05/05/2022 21:09, Java Jive wrote:
>>
>> I think the argument about the amount of atmosphere the signal has to
>> travel through is the most convincing so far suggested.
>
> There should be sufficient information here
> http://www.apsattv.com/techinfo/predicting-out-of-footprint-coverage.htm
> to answer your question with facts rather than speculation.

Thanks, interesting in its own right, but doesn't answer my question.

--

Fake news kills!

I may be contacted via the contact address given on my website:
www.macfh.co.uk

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From: me...@privacy.invalid (NY)
Newsgroups: uk.tech.digital-tv
Subject: Re: Satellite Dishes & Calculations
Date: Fri, 6 May 2022 13:02:46 +0100
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 by: NY - Fri, 6 May 2022 12:02 UTC

"MikeS" <MikeS@fred.com> wrote in message news:t52nph$cdc$1@dont-email.me...
>>>> In the SE of England 28.2E the elevation is 25 degrees - in Scotland
>>>> its 20 degrees. Possibly the same reason why a setting sun closer to
>>>> the horizon is red - the light travels further through the atmosphere.
>>
>> Yes.
>>
>>> Except the signal also similarly fades on all edges of the footprint
>>> (which blows my theory out of the water too)
>>>
>>> https://en.satexpat.com/coverage/east/28.2/
>>
>> I don't dispute that the signal fades towards the edge of coverage, but
>> if you look at the coverage map there, coverage is centred on the British
>> Isles as a whole, so if the need for a larger dish was due to fading of
>> the signal towards the edge of coverage, the border area should be
>> getting a stronger signal than the south coast of England, and therefore
>> a smaller dish should be needed in the borders, and a larger one on the
>> south coast, whereas reality is the other way round!
>>
>> I think the argument about the amount of atmosphere the signal has to
>> travel through is the most convincing so far suggested.
>>
> There should be sufficient information here
> http://www.apsattv.com/techinfo/predicting-out-of-footprint-coverage.htm
> to answer your question with facts rather than speculation.

This is probably a really silly question, but I've always wondered why the
satellite that covers the UK is on a longitude of 28.2 deg E rather than
being at or near 0 degrees since that's the approximate longitude of the UK?
28.2E is the longitude of Ukraine/Belarus/Turkey.

Is there a reason why they don't want dishes to point vaguely south (or
north in the southern hemisphere), and instead to point vaguely south-east
(for UK)?

I'd have thought that a satellite that is designed to cover an area with a
given longitude should be placed roughly at the longitude.

I'm probably about to learn something...

Re: Satellite Dishes & Calculations

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From: ton...@bancom.co.uk (tony sayer)
Newsgroups: uk.tech.digital-tv
Subject: Re: Satellite Dishes & Calculations
Date: Fri, 6 May 2022 13:04:20 +0100
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 by: tony sayer - Fri, 6 May 2022 12:04 UTC

In article <t52qam$r6v$1@dont-email.me>, David Woolley <david@ex.djwhome
..demon.invalid> scribeth thus
>On 05/05/2022 18:22, Tweed wrote:
>> At 10 GHz atmospheric attenuation is 0.02dB per km, propagating
>> horizontally at sea level.
>
>That's only in good weather. Rain causes a lot of attenuation. Whilst
>I don't know exactly how much, uplink powers have to be controlled to
>avoid overloading transponders when there is no rain, whilst providing
>enough signal in rain.

Yes it does! Remember working at a local radio station here one day the
mother of thunderclouds turned up off went the sat fed IRN news feed
shortly followed by the ASTRA 28.2 feed killed them totally till the
cloud moved i on sky was almost black!

Don't some riggers use a damp cloth over a LNB to make measurements
easier i.e. introducing some attenuation?.

Same issue with higher frequency waves from the old Sun at higher
latitudes!
--
Tony Sayer

Man is least himself when he talks in his own person.

Give him a keyboard, and he will reveal himself.

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Subject: Re: Satellite Dishes & Calculations
From: notyalck...@gmail.com (R. Mark Clayton)
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 by: R. Mark Clayton - Fri, 6 May 2022 15:30 UTC

On Thursday, 5 May 2022 at 15:47:29 UTC+1, Java Jive wrote:
> One for the pros here. According to this site ...
>
> Satellite Dish Suggested Minimum Sizes
> https://www.smartaerials.co.uk/blog/what-size-satellite-dish-do-i-need
>
> "The further you’re away from the satellites in space the weaker the
> received signal will be. As the satellites remain in geostationary orbit
> around the equator the further in the UK north in the UK you are
> installing your satellite dish the weaker the received signal will be,
> meaning that satellites dishes installed in the north of England and
> satellite usually require a larger dish that those using a comparable
> service in the south of England."
>
> I don't dispute the need of the larger dish, but I'm suspicious of the
> reason given, not just because it is garble-worded, but more importantly
> as follows ...
>
> The radius of earth is about 6,371 km
> The radius of the Clarke Belt is 42,164 km
> The south coast of England is around 50 degrees N
> The border between England & Scotland is around 55 degrees N
>
> There is a nice little triangle solver here:
> https://www.calculator.net/triangle-calculator.html
>
> Putting the above into it gives us:
>
> South Coast distance to Clarke Belt = 38,380 km
> https://www.calculator.net/triangle-calculator.html?vc=&vx=6371&vy=&va=50&vz=42164&vb=&angleunits=d&x=62&y=34
>
> Border distance to Clarke Belt = 38,862 km
> https://www.calculator.net/triangle-calculator.html?vc=&vx=6371&vy=&va=55&vz=42164&vb=&angleunits=d&x=62&y=34
>
> I accept that I haven't allowed for the sats being at 28E rather than
> due south, but this is good enough to tell us that, for the two example
> locations above, the order of magnitude of the difference in distance
> from sat to dish is likely to be only around 1%, and, even after
> applying the inverse square law, one would think that's not enough to
> justify a substantially larger dish?
>
> So what is the real reason for the greater size of dish needed?
>
> --
>
> Fake news kills!
>
> I may be contacted via the contact address given on my website:
> www.macfh.co.uk

There are several real reasons: -

1. Further away, although not that much.
2. Beam centre will probably be aimed at southern England, so in Scotland you will be off the narrow beam with a weaker signal. (works the other way too, you CAN pick up UK channels in Spain, but you need a BIG dish).
3. More atmospheric attenuation - more signal lost passing through more atmosphere.

Re: Satellite Dishes & Calculations

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From: dav...@ex.djwhome.demon.invalid (David Woolley)
Newsgroups: uk.tech.digital-tv
Subject: Re: Satellite Dishes & Calculations
Date: Fri, 6 May 2022 16:50:53 +0100
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 by: David Woolley - Fri, 6 May 2022 15:50 UTC

On 06/05/2022 13:02, NY wrote:
>
> Is there a reason why they don't want dishes to point vaguely south (or
> north in the southern hemisphere), and instead to point vaguely
> south-east (for UK)?

Due South would put the Sun in the centre of the receiver main lobe
twice a year. The noise temperate of of the Sun is about 6,500K,
whereas a good LNB might have a noise temperature of a few tens of K,
and space could be as low as about 3K.

Being out on the limb of Europe might be another factor.

Re: Satellite Dishes & Calculations

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Subject: Re: Satellite Dishes & Calculations
From: notyalck...@gmail.com (R. Mark Clayton)
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 by: R. Mark Clayton - Sat, 7 May 2022 09:05 UTC

On Saturday, 7 May 2022 at 00:16:03 UTC+1, Java Jive wrote:
SNIP

> > There are several real reasons: -
> >
> > 1. Further away, although not that much.
> No, sorry, but this just cannot be the explanation. Consider ...
>
> The calculation still quoted above for a satellite due south is a worst
> case analysis, and the difference in distance is 482 km as a fraction of
> 38,380 km ...
> 482 / 38380 = 1.3% (rounded up)
> ... whereas for a satellite out at 28.2E, we would have ...
> smaller number than 482 / greater number than 38,380
> ... which must be a smaller percentage than the above, which anyway was
> rounded up, so the difference in distance just cannot be greater than
> around 1.2%. See also the discussion about the elliptical shape of the
> coverage pattern below.
>
> Now think of the dish sizes for Zones 1 & 2, here's a dish available as
> either Zone 1 or Zone 2...
> https://www.amazon.co.uk/Satellites-Zone-Satellite-Dish-FreeSat-2-NO-QUAD/dp/B077DQTPYX/ref=sr_1_16
> ... which is ...
> Zone 1: 60 x 40 cm
> Zone 2: 80 x 60 cm.
>
> The boresight cross-sectional area for each of these dishes is Pi.a.b
> where a and b are the semi-major and semi-minor axes respectively. So
> we have ...
> Zone 1 Cross-sectional Area: 1,885 cm2
> Zone 2 Cross-sectional Area: 3,769 cm2
> ... so a doubling of cross-sectional area.
>
> I don't see how a 1% increase in distance can explain a doubling of dish
> area!

"not that much" about 2.5% based on your figures.

> > 2. Beam centre will probably be aimed at southern England, so in Scotland you will be off the narrow beam with a weaker signal. (works the other way too, you CAN pick up UK channels in Spain, but you need a BIG dish).
> No again, look at the coverage map in the link given by Mark Carver.
>
> The area of strongest signal includes the entire UK except Shetland, the
> entirety of the island of Ireland, and Normandy. Shetland is in the
> fringe zone, as probably is Iceland though this is not shown on the
> coverage map (I think someone said recently here that you could get
> British satellite TV in Iceland).
>
> The coverage pattern is roughly elliptical, which is exactly what you'd
> expect from a conical beam, circular in cross-section, irradiating the
> curved surface of the earth at a slanted angle. Again as expected, the
> semi-major diameter lies along the line from 28.E, going roughly from
> Thanet through Liverpool and the Isle Of Man and onwards between
> Scotland and Northern Ireland. This means that, say, Aberdeen is about
> the same distance from it as St Ives or Lands End in Cornwall, they are
> each about 260 miles or 420 km straight line distance from Liverpool,
> and therefore, based on distance from the centre of coverage alone,
> these two places should require about the same size of dish. But, see
> also below.
>
> Note: There is a cutout in the Atlantic, but, in the absence of
> evidence to the contrary, I assume that this is entirely fictional,
> caused merely by lack of data because no-one lives in the Atlantic, and
> that actually the coverage pattern is actually near-elliptical. It's
> not truly elliptical because as the earth's surface curves away from the
> satellite into the North Atlantic, the coverage is spread over a wider
> area and, despite the cutout, this spreading is noticeable in the
> coverage map.

Depends on the satellite and transponder, some are fairly wide beams, others quite narrow.

> > 3. More atmospheric attenuation - more signal lost passing through more atmosphere.
> Yes, my first reaction before making my OP was to guess that this might
> be a major cause of the need for a bigger dish, and many replies since
> have also mentioned this. Now, having understood the near-elliptical
> nature of the coverage pattern as above, we can do some calculations for
> the two locations previously established to be equidistant NE and SW
> from its semi-major diameter. Putting these two places into a sat
> calculator reveals that, although there is about 437 km difference in
> distance to the sat (so, as predicted, less than that given in the first
> calculation for a satellite due south, and divided by a greater distance
> = smaller percentage change), the main difference is the elevation
> settings required, 19.8 and 24.3 degrees, so, in the absence of other
> more convincing suggestions, greater attenuation of the signal
> travelling a greater distance through the atmosphere does indeed seem to
> be the cause of the need for a bigger dish.

Indeed maybe I should have put it first. About 2.5 times as much atmosphere by rough calculation, depending on latitude

>
> Aberdeen (57.13,-2.10)
> https://satlex.de/en/azel_calc-params.html?satlo=28.2&location=57.13%2C-2.10&la=57.13&lo=-2.10&country_code=uk
>
> Azimuth angle: 145.17° (True North)
> Elevation angle: 19.83°
> ...
> Distance to satellite: 39578.52 km
>
> St Ives, Cornwall (50.20861,-5.4875)
> https://satlex.de/en/azel_calc-params.html?satlo=28.2&user_satlo_dir=E&la=50.20861&lo=-5.4875&country_code=uk
>
> Azimuth angle: 139.06° (True North)
> Elevation angle: 24.31°
> ...
> Distance to satellite: 39141.72 km
> --
>
> Fake news kills!
>
> I may be contacted via the contact address given on my website:
> www.macfh.co.uk

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Subject: Re: Satellite Dishes & Calculations
From: notyalck...@gmail.com (R. Mark Clayton)
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 by: R. Mark Clayton - Sat, 7 May 2022 09:10 UTC

On Friday, 6 May 2022 at 16:50:55 UTC+1, David Woolley wrote:
> On 06/05/2022 13:02, NY wrote:
> >
> > Is there a reason why they don't want dishes to point vaguely south (or
> > north in the southern hemisphere), and instead to point vaguely
> > south-east (for UK)?
> Due South would put the Sun in the centre of the receiver main lobe
> twice a year. The noise temperate of of the Sun is about 6,500K,
> whereas a good LNB might have a noise temperature of a few tens of K,
> and space could be as low as about 3K.
>
> Being out on the limb of Europe might be another factor.

The sun still appears behind the satellite for two short periods each year.

Originally $ky used 19.2 E, which is about the same longitude as Warsaw, but since it went digital it is on 28.2E, which is the about the same longitude at central Ukraine.

Given most of the UK is west of Greenwich it does seem and odd choice.

OTOH with my steerable dish I could see from 42E (shed in the way) to 45W.

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Subject: Re: Satellite Dishes & Calculations
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 by: Java Jive - Sat, 7 May 2022 11:49 UTC

On 07/05/2022 10:05, R. Mark Clayton wrote:
>
> On Saturday, 7 May 2022 at 00:16:03 UTC+1, Java Jive wrote:
> SNIP
>>>
>>> There are several real reasons: -
>>>
>>> 1. Further away, although not that much.
>>
>> No, sorry, but this just cannot be the explanation. Consider ...
>>
>> The calculation still quoted above for a satellite due south is a worst
>> case analysis, and the difference in distance is 482 km as a fraction of
>> 38,380 km ...
>> 482 / 38380 = 1.3% (rounded up)
>> ... whereas for a satellite out at 28.2E, we would have ...
>> smaller number than 482 / greater number than 38,380
>> ... which must be a smaller percentage than the above, which anyway was
>> rounded up, so the difference in distance just cannot be greater than
>> around 1.2%. See also the discussion about the elliptical shape of the
>> coverage pattern below.

It's actually 1.1%.

>> Now think of the dish sizes for Zones 1 & 2, here's a dish available as
>> either Zone 1 or Zone 2...
>> https://www.amazon.co.uk/Satellites-Zone-Satellite-Dish-FreeSat-2-NO-QUAD/dp/B077DQTPYX/ref=sr_1_16
>> ... which is ...
>> Zone 1: 60 x 40 cm
>> Zone 2: 80 x 60 cm.
>>
>> The boresight cross-sectional area for each of these dishes is Pi.a.b
>> where a and b are the semi-major and semi-minor axes respectively. So
>> we have ...
>> Zone 1 Cross-sectional Area: 1,885 cm2
>> Zone 2 Cross-sectional Area: 3,769 cm2
>> ... so a doubling of cross-sectional area.
>>
>> I don't see how a 1% increase in distance can explain a doubling of dish
>> area!
>
> "not that much" about 2.5% based on your figures.

No, the difference in distance is only 1.1%, and even were it 2.5%, it
still wouldn't explain a doubling in dish cross-sectional area.

>>> 3. More atmospheric attenuation - more signal lost passing through more atmosphere.
>>
>> Yes, my first reaction before making my OP was to guess that this might
>> be a major cause of the need for a bigger dish, and many replies since
>> have also mentioned this. Now, having understood the near-elliptical
>> nature of the coverage pattern as above, we can do some calculations for
>> the two locations previously established to be equidistant NE and SW
>> from its semi-major diameter.

Oops, should have been major diameter.

>> Putting these two places into a sat
>> calculator reveals that, although there is about 437 km difference in
>> distance to the sat (so, as predicted, less than that given in the first
>> calculation for a satellite due south, and divided by a greater distance
>> = smaller percentage change), the main difference is the elevation
>> settings required, 19.8 and 24.3 degrees, so, in the absence of other
>> more convincing suggestions, greater attenuation of the signal
>> travelling a greater distance through the atmosphere does indeed seem to
>> be the cause of the need for a bigger dish.
>
> Indeed maybe I should have put it first. About 2.5 times as much atmosphere by rough calculation, depending on latitude

[snip]

>> --

^ Correctly, there is a space here, so this should have been
recognised as the beginning of a sig.

>>
>> Fake news kills!
>>
>> I may be contacted via the contact address given on my website:
>> www.macfh.co.uk

Your ng software seems to be having a problem with recognising valid sigs.

--

Fake news kills!

I may be contacted via the contact address given on my website:
www.macfh.co.uk

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