0.01dB lnb?

Lancelot said:
Hmmmm.................. :D


Anyone checked the DATE at all ???


L.:)
Click to expand...
This is what the firm tells us when we click "Add to Chart"

Thank you for your faith in us.
However, there's no such thing as a 0.01dB LNB. In fact I wouldn't believe any claims of noise factors below 0.3dB. The best LNB we can offer is the Invacom range but these will not fit on a Sky minidish. You would have to buy a dish that has a 40mm LNB clamp. The good news is that the Invacom LNBs don't cost anywhere near £199. Of course, in the UK, the Sky signals are strong so you won't need a special LNB. Any universal LNB will do the job. The only way to increase the signal is to use a larger dish.
:-rofl2
[SIZE=+1][/SIZE]
 
jaju said:
The only way to increase the signal is to use a larger dish.
:-rofl2
Click to expand...

I dont mean to be controversial my friend but that is just not an accurate statement as there are a number of ways to increase signal to noise using the same dish.

Lower Noise Figure LNB
Better Illumination Efficiency
Lower Spillover Loss

are just a few ways.

Personally I wouldnt believe ay claims of Noise Figure below 0.7dB at ku-band from any of the normal Sat TV LNB manufacturers but it is possible to get below this figure with special Low Noise Amplifiers that are not easily available to us.
 
So, to get to the point, what are the best ku band lnb's around - mti? invacom?
 
Hmm - I wonder if SMW are still using the HP8970B Noise Figure Meters that they tested their LNB's with back in the early '90's? This had a measurement uncertainty of +/- 0.3dB.

Quote from their 1996 catalogue -

Measurement Uncertainties

"Despite the use of advanced measurement equipment you will still have some uncertainties to consider. There is an instrument uncertainty in the Noise and Gain analyser of +/- 0.3dB, the noise source has an uncertainty of +/- 0.07dB and there is a mismatch uncertainty of +/- 0.1 dB. This gives a worst case uncertainty of 0.2 dB or a RSS (Root Sum of Squares) of 0.12dB.

But this is however not all. There is another source of error which few people are aware of. The noise source impedance changes slightly between the "cold" and "hot" state resulting in that the LNB "sees" a difference in impedance at the input. This change in impedance does affect the gain of the LNB which also changes with the "cold" and "hot" state of the noise source. This causes the LNB to change the NF and, what is worse, the gain of the LNB during the measurement. Since the analyser measures the ratio between "cold" and "hot" state this can result in a significant error in the noise figure measurement. And this error can be up to 0.3 dB. There is however a way to reduce this error. This is to use a noise source with very little difference in the impedance between "cold" and "hot" states. There are noise sourses available with an extra 10 dB built in attenuator which reduces the impedance variation considerably."

Presumably the NF figures of the currently available SMW LNB's are based on measurements taken with these meters?

Llew
 
Llew said:
Hmm - I wonder if SMW are still using the HP8970B Noise Figure Meters that they tested their LNB's with back in the early '90's? This had a measurement uncertainty of +/- 0.3dB.

Quote from their 1996 catalogue -

Measurement Uncertainties

"Despite the use of advanced measurement equipment you will still have some uncertainties to consider. There is an instrument uncertainty in the Noise and Gain analyser of +/- 0.3dB, the noise source has an uncertainty of +/- 0.07dB and there is a mismatch uncertainty of +/- 0.1 dB. This gives a worst case uncertainty of 0.2 dB or a RSS (Root Sum of Squares) of 0.12dB.

But this is however not all. There is another source of error which few people are aware of. The noise source impedance changes slightly between the "cold" and "hot" state resulting in that the LNB "sees" a difference in impedance at the input. This change in impedance does affect the gain of the LNB which also changes with the "cold" and "hot" state of the noise source. This causes the LNB to change the NF and, what is worse, the gain of the LNB during the measurement. Since the analyser measures the ratio between "cold" and "hot" state this can result in a significant error in the noise figure measurement. And this error can be up to 0.3 dB. There is however a way to reduce this error. This is to use a noise source with very little difference in the impedance between "cold" and "hot" states. There are noise sourses available with an extra 10 dB built in attenuator which reduces the impedance variation considerably."

Presumably the NF figures of the currently available SMW LNB's are based on measurements taken with these meters?

Llew
Click to expand...

I have no idea which equipment SMW use today but I still have more faith in the numbers they quote and they are definately more accurate than say Invacom or Sharp etc. If SMW are still using these old Noise Figure Meters then of course we still have some uncertainty but if they are using the latest generation of equipment then that uncertainty is much lower. Any decent maufacturer will leave a small safety margin in the quoted figure or clarify it as typical or peak etc.

Lets face it you also get the same impedance changes when you attach the LNA to a feedhorn or when you change the elevation of the dish or when you change frequency across the band so we have uncertainties across the board, you also get Noise Temperature changes as the LNA/LNB temperature changes so there are a lot of variables.

I just think its unfair that many people go out an buy the latest Super LNB just because the manufacturer makes a wild claim about performance thats completely untrue and unproven.
 
Hi guys

What about the 0.2dB LNBs from Chess, any good? Would you see an improvement on the Invacom 0.3dB?

Yan
 
Hi,

I heard one Greek company made a 'special edition' 0.1 dB lnb. I think it was Chess.

So how does one go about building a special low-noise amplifier? Where can I get the parts? How to build and implement that Maser laser into the sat system?

Or maybe just cooling a normal LNB is enough for great results. I read in TELEVISION and electronics mag 2 years ago that a man in New Zealand was cooling his LNB.
 
divibi said:
Hi,

I heard one Greek company made a 'special edition' 0.1 dB lnb. I think it was Chess.
Click to expand...

If they claim 0.1dB Noise Figure then the spec is false so who knows unless you can do a direct comparison.

divibi said:
So how does one go about building a special low-noise amplifier? Where can I get the parts? How to build and implement that Maser laser into the sat system?
Click to expand...

You need to do a lot of reading for starters to even begin to understand the problems associated with designing these things. I dont know of anyone that produces a kit of parts either at the moment but maybe someone else does ??

divibi said:
Or maybe just cooling a normal LNB is enough for great results. I read in TELEVISION and electronics mag 2 years ago that a man in New Zealand was cooling his LNB.
Click to expand...

You will need to make a refrigerator unit that is capable of cooling to very low temperatures around -100 degrees C or less. Not very easily done at home.
 
How about pouring some liquid nitrogen on your LNB with someone watching the screen (or taping it) and seeing what happens. :D

Best doing it on some faint analog channel to see the difference.
 
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