LNB for C band ?17deg

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kevincraky

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#39809 19-Aug-2009 17:24

LNB for C band ?17deg I was told that I need a 13 deg. not a 17 deg. for C band LNB to get good reception for chinasat6

I was told I have 2 new C band LNB from 2 diferent manufacturers one is a BORL this BORL seems usless

There is this one forsale in Christchurch on trademe

" ASK-BC224 C band LNBF
C Band dual polarity LNBF
I/P Freq. 3.4~4.2 Ghz
L.O. 5150 Mhz
O/P Freq. 950~1750 Mhz
Gain 62db
Noise Temp 15 K

is it true the difference between 17 and 15 gets me better reception for Chinasat6 ?

Kevin Clancy Architectural Designer

cyril7

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#248731 19-Aug-2009 18:57

Hi, most of these LNBs are made in China by companies of dubious repute, the quality of there wares can be all over the place, the reliability you can hang on their Noise Temp should be taken with a bar of soap.

Get an LNB from a reliable source, try Satmax they are in ChCh, while their LNBs probably also come from a Chinese factory they will ensure that what you get will work or you can take them back. Chinasat6 is not hard to get assuming you are in a location that can see the satellite (which is only around 15deg elevation depending on exactly where you are) other than that and the need for at least a 2.4m dish its not hard to get, no super performance nitro powered LNB needed.

Cyril

kevincraky

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#248782 19-Aug-2009 20:35

Its not the cost but the unsightliness of such a big dish - I have been able to get 6 good channels on my 1.2 meter dish - I am now becoming aware as you have pointed out that some of these LNBs are quite week. Perhaps it is bad quality control or it is the specs or the brand - I have 2 different LNBs with the same specs but one is useless for my needs. I see a Guy selling one on trademe with what appears to have a better spec than the 2 that I have - the Dealers sell for tripple price and for all I know they might be the same ?

Kevin Clancy Architectural Designer

cyril7

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#248884 20-Aug-2009 07:08

Hi, while you might get one or two of the stronger transponders with a 1.2m dish you will be running on the edge of margin, hence you are picking up differences in probably otherwise good LNBs. I suggest you increase the size of you dish and you will find both LNBs will work fine.

The signal strengths that Chinasat6 presents here really demands a bigger dish otherwise you will find other parts of the equation wont work, (ie no one makes a LNB that will work at those signal levels).

Chinasat state that the predicted power level over NZ is 36dBW which will require a 1.6-2.0m dish, a 1.2m dish is recommended for power levels of around 39-40dBW, thats a 3dB difference. From my experience teh 1.6-2.0m recommendation is still marginal, hence for reliable reception most installers use 2.4m dishs. If you choose to use smaller than recommended then there is a penalty to pay.

If you choose not to operate gear in its recommend margin then cannot expect reliable results. Its a bit like complaining that your new Toyota Corolla keeps overheating when you run it 3hrs continuous at 180km/hr, if you intend to do that then purhaps you should go for the larger Lexus models.

Cyril

Jaxson

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#248919 20-Aug-2009 09:11

Your Corrolla can get past 95km/hr?!

kevincraky

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#248930 20-Aug-2009 09:26

OK fair enough - here is a question - is it absolutely totally impossible to uses 2 dishes with 2 LNBs to go into one receiver box?

Kevin Clancy Architectural Designer

cyril7

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#249048 20-Aug-2009 14:29

Hi, its no problem to have two dishes with a LNB on each going to one STB, you can use either a 22kHz switch, Disqec switch or full multiswitch all depending on what level of flexibility you require.

Cyril

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kevincraky

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#249054 20-Aug-2009 14:42

I think I worded dat wong - silly me What I ment was can I or could I get 2 dishes pointed at the same sat
and double up the power to the box - say instead of one 2.4 dish I use 2 1.2 dishes to get a strong enough signal????

Kevin Clancy Architectural Designer

cyril7

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#249057 20-Aug-2009 14:49

Oh ok, no while technically it is possible, in practice its simply not possible to get close enough phase alignment to make it work, in radio astronomy it is commonly used, however they have some fearfull computer power behind it to make it happen, so no forget that idea.

Cyril

richms

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#249151 20-Aug-2009 18:20

No you cant, you would need the local oscilators in them locked together - otherwise they will just beat in and out making the resulting signal a total mess.

And you would need to have the phase perfect with the combination.

And the losses in the combiner would negate any increase in signal.

Just install the recommended sized dish.

Richard rich.ms