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Trying to make a decision, 1.8m or 1.2m

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Ex Member
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Mar 3rd, 2009 at 1:58pm  
I was looking for some of your opinions in regards to dish size selection.  Is it worth an additional $1000 to upgrade to the 1.8m dish from the 1.2m?  How much does the difficulty increase in pointing and setting up the 1.8m?

Thanks for the help!
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Eric Johnston
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Reply #1 - Mar 3rd, 2009 at 6:10pm  
Receive:
Assuming no change in the carrier power or modulation towards you then you will improve your downlink rain margin which means less outage time per year due to heavy rain.
Assuming no change in carrier power towards you may be able to change the modulation and coding at the far end to reduce your receive satellite costs by perhaps 2/3.
Assuming a reduced power carrier towards you this will reduce satellite costs and ease the transmit power requirements needed at the other end.

Transmit:
Assuming no change in your uplink power you will be able to buy a cheaper BUC (For example, if you were contemplating a 16W BUC to go with 1.2m dish you would save money by choosing 8W BUC and 1.8m dish)
Alternatively, using the same BUC you will be able to double your uplink transmit bit rate.

Regardless of dish size, the mounting needs to be rock steady.  Pointing involves 1/6th turn increments of the nuts to peak up.  In my experience larger dishes have finer threads on the az/el screws so there is no difference in the sensitivity of the adjustments.  The larger dish does require more concrete etc., but I would not let this discourage you.

The off-axis discrimination (on-axis gain versus sidelobe gain) improves with larger dishes and so the interference received from and sent to adjacent satellites reduces.  This is particularly important where the satellites are being operated close together.  If you want to transmit a high density carrier (i.e. a lot of BUC watts in a narrow bandwidth) the satellite operator will insist on you using a large dish.

Best regards, Eric.
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Reply #2 - Mar 3rd, 2009 at 10:57pm  
I am extremely new to the whole setup, I am not sure what the BUC is so I definetly do not know the specs.  I actually have never set up a system before.  It will be a Bentley-Walker setup with the Hughes HX50 if you might know what that would come with.  Otherwise I will ask their sales rep if he could provide me the information.

Also you mentioned changing the code and modulation.  Is there a good article or wiki you could point me in the right direction for that?

Thanks!!
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Reply #3 - Mar 3rd, 2009 at 10:59pm  
I also just noticed that I accidentally posted this in the LinkStar Forum... If one of the moderators would move it to the appropriate forum, my apologizes.
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Reply #4 - Mar 4th, 2009 at 9:02am  
If it is Hughes HX from Bentley Walker you will be normally be provided with a modern 1.2m Prodelin dish with exceptionally good cross-pol performance and with the polarisation scale behind the dish.

In exceptional cases a 1.8m dish will be recommended if you are at the extreme edge of the beam coverage. Follow their advice.

The HX system copes well with rain fading and operation in weak signal areas by adaptive coding and modulation.

Best regards, Eric.
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« Last Edit: Mar 4th, 2009 at 11:47pm by Admin1 »  
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Reply #5 - Mar 4th, 2009 at 12:32pm  
Quote:
If it is Hughes HX from Bentley Walker you will be normally be provided with a modern 1.2m Prodelin dish with exceptionally good cross-pol performance and with the polarisation scale behind the dish.

In exceptional cases a 1.8m dish will be recommended if you are at the extreme edge of the beam coverage. Follow their advice.

The HX system copes well with rain fading and operation in weak signal areas by adaptive coding and modulation.

Best regards, Eric.


Thanks for the help.  So it would be your suggestion due to the capabilities of the HX system to not upgrade to the 1.8m dish unless we are on the extreme edge of the beam coverage?
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« Last Edit: Mar 4th, 2009 at 11:46pm by Admin1 »  
 
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Eric Johnston
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Reply #6 - Mar 4th, 2009 at 7:40pm  
If you are in a very heavy rain area and minimal outage is important to you, you might consider it worthwhile.

Best regards, Eric.
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« Last Edit: Mar 4th, 2009 at 11:45pm by Admin1 »  
 
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Reply #7 - Mar 12th, 2009 at 2:36pm  
Thanks for the assistance, I think I will end up going with the 1.2m
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Reply #8 - Mar 12th, 2009 at 10:48pm  
Hi this is Tony Walker , if you mail me I will check where you are BUT all our service plans are based on 1,2 mtrs dish , I would highly doubt you need a 1,8 my email adress is anthony@bentleywalker.com
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