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  Reply # 490925 8-Jul-2011 09:21
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Checked my signal last night, ~6:30. The signal quality was at 94%, which is what it usually is. No problem with the picture. 65cm dish in Wellington.

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  Reply # 490927 8-Jul-2011 09:24
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dolsen: Checked my signal last night, ~6:30. The signal quality was at 94%, which is what it usually is. No problem with the picture. 65cm dish in Wellington.

Yea same.  With Mediaportal, Hauppauge DVBs Cards, 90 cm Dish I'm sitting at 100% Signal Quality ... where as around 5:00pm area it was pretty much at 0%.  Overnight and this morning its back to where it was before the problems started a few days ago.

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  Reply # 490953 8-Jul-2011 10:11
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I got nothing overnight, but it was grotty weather in Wellington.

Question - the installer of my new 65cm dish said dish size has no impact on signal. Is this true? He was the expert, so I took his word.

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  Reply # 490955 8-Jul-2011 10:13
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password1: I got nothing overnight, but it was grotty weather in Wellington.

Question - the installer of my new 65cm dish said dish size has no impact on signal. Is this true? He was the expert, so I took his word.

Id say "rubbish" ... imagine if you had a 10cm dish ... you would be always be impacted by rain fade etc.

For Freeview and having a 65cm or a 90cm+ ... Id say that "could" be the case since the signals from Freeview are pretty strong, but not for SBS. 

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  Reply # 490958 8-Jul-2011 10:21
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With a few provisos, what you were told is correct. If you only want to receive Freeview, and you only consider dishes bigger than about 30 cm, and "signal" is taken to mean that reception is effectively flawless, and the occasional instance of rain-fade is acceptable, then dish size makes no difference. For an expert talking casually to the run-of-the-mill Freeview client, it's probably OK.

It's by no means the whole truth under all circumstances though, indeed it is nonsense in the general case, for if it were true, having a dish of zero size would allow perfect reception from Andromeda!

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  Reply # 490970 8-Jul-2011 10:33
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The conversation was about the merits of 65cm vs 90cm on picking up SBS. I thought it was odd, as I've seen plenty of large dishes outside houses that I assumed were that large of reasons of coverage or sensitivity

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  Reply # 490982 8-Jul-2011 10:55
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Again, that's probably true. If you can get SBS on a 65, there isn't a lot of benefit in moving to a 90. It's digital. It either works perfectly or fails badly. (Another sweeping generalisation!)

I opted for a 90 cm dish as my line of site was only just clearing some trees, I wanted to reduce or eliminate the incidence of rain-fade from an already low level, and I wanted the option of adding a C-band LNB to pick up Intelsat 5 at a later date. That last factor would probably mean repointing the dish at I5 as the signal from there is relatively weak, and using an offset LNB for Optus D1, which, I think, could reduce the efficiency of the dish. Finally, as it was a new installation, the cost of a 90 was about $20 more than a 65, so why not? Any larger though, and roof mounting does become more problematic.

In extending that argument a bit, you'll often see large dishes where reception is from satellites other than Optus D1 and services, possibly C-band rather than Ku, where the amount of signal hitting the dish is a lot lower.

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Reply # 491038 8-Jul-2011 13:01
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There is some old wives tales going around about satellite dishes watching SBS

The old formula .7854 by D square applies to dishes, you can forget about the Pi/4 or .7854, which is a constant.  One by increasing the area of the dish from 60cm to 90cm, which is 1.5 squared = 2.25, in a near enough figure, that equates to over three db gain (3.5 db exactly), or double the signal strength.  Here is the big plus; furthermore you also drop the atmospheric noise level down by 3 db (3.5 db exactly).  So technically in the end your new 90 cm dish ends up with a 6-db gain over a 60 cm dish (4 times the signal strength). 

You replace your 60cm with a 6-meter dish, therefore your antenna would have 20-db gain (10 by 10 = 100), and allowing for the atmospheric noise reductions, this would have a beneficial gain of 40db.  Another problem manifest itself is the focusing adjustments on to a satellite with a dish of this size; these adjustments would be very sharp and critical. 

Inherent receiver noise whether from the LNB, cable, or receiver circuitry is a constant.  Unless you want to go into the impossible realms of helium cooling and one is talking about 40 degrees Kelvin.  

 

if doubt use a bigger dish

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  Reply # 491055 8-Jul-2011 13:15
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SBS 1 & 2 solid into Wgtn - but still only registering 85% on my Ultraplus 700HDMI off my Sky dish at 1315NZ Friday.

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  Reply # 491160 8-Jul-2011 16:03
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password1: I got nothing overnight, but it was grotty weather in Wellington.

Question - the installer of my new 65cm dish said dish size has no impact on signal. Is this true? He was the expert, so I took his word.


Maybe you should ask him why Sky routinely install 90cm on commercial installs ;-)

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  Reply # 491428 9-Jul-2011 15:14
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Am I the only person in Wellington still not picking up SBS that reads this thread?

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  Reply # 491432 9-Jul-2011 15:37
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Still OK here...o/cast
Q level back up same as 12401 now

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  Reply # 491438 9-Jul-2011 16:00
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Username01: SBS 1 & 2 solid into Wgtn - but still only registering 85% on my Ultraplus 700HDMI off my Sky dish at 1315NZ Friday.


And at 1600NZ Saturday in a wet & overcast Wgtn, both register at 94%. A weird episode.

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  Reply # 491450 9-Jul-2011 16:46
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Seems at present to be back to normal signal strengths.

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  Reply # 491466 9-Jul-2011 18:18
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Grrr, just me then. Signal disappeared mid week and hasn't come back. Can still tune my Nova-S cards into it, but simply no picture. Rapidly losing WAF.

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