0.01dB lnb?

kamaleon

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#1
hmmm.... what the heck is the score with this lnb:
_http://www.satcure.co.uk/no_lnb.htm

0.01dB? Receive tv from Australia on a minidish?

:eek: or O-no?
 

Lancelot

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#2
Hmmmm.................. :D


Anyone checked the DATE at all ???


L.:)
 

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#3
Read their disclaimer...

None of the material contained in the Sites is to be relied upon as a statement or representation of fact.
 

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#4
bid0n said:
hmmm.... what the heck is the score with this lnb:
_http://www.satcure.co.uk/no_lnb.htm

0.01dB? Receive tv from Australia on a minidish?

:eek: or O-no?
Smells of Extract of Urine to me.... O-Ha
 

kamaleon

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#5
No wonder why satcure's the only hit when you google for 0.01LNB then!!!

:-rofl2:-rofl2:-rofl2
:-doh! what are they fkc'ng like....

well spotted dudes
 

Hitchcock

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#7
An LNB with a noise figure of 0.01 dB would also not give 200% signal strength (whatever that means), it would raise the C/N however over a normal Sky LNB (0.6 d:cool: by x 63, meaning the Sky minidish (45 cm) would behave like a 3.6 m dish with a normal Sky LNB.
 

divibi

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#8
Hello everyone!

Hitchcock,
Is such an LNB of 0.01 db at all feasible in the world of physics? What if it's made out of real gold, platinum or better. Is a true 0.1 db possible (not just a sticker figure)? What is the way to improve LNBs; maybe sub zero cooling or something? Anyone has any suggestions?
 

Hitchcock

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#9
Hi divibi,

I don't know what the physical limit is, I asked a question about this once, and I was told that there is always some background noise, 4 deg Kelvin, which corresponds to a noise figure of 0.06 dB.

I also asked a reputable LNB manufacturer once, SMW, and they told me they were using the best transistors (HEMT) available at the time, their top-perfoming LNB has a noise figure of 0.8 dB and it is the same noise figure they had back in 1995. With the arrival of the Invacom 0.3 dB back in 2002 I could finally see a better picture over what the SMW 0.8 dB offered, but not by very much. Going by the actual improvement I saw over the SMW, the Invacom is probably no better than 0.5 dB in reality.

As for golden LNBs etc, someone once told me that if you coated the 'needle' inside your LNB with pure gold, you would improve your signal a tiny bit ... I have no idea if you could actually see this improvement on your TV screen though.

Your idea about sub zero cooling is interesting. Maybe we could try something like this (photo stolen from the web)!

 

ouagadougou

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#10
A Noise Figure of 0.8dB is still a realistic minimum at ku frequencies. The gain of successive transistor devices has improved over the years so that when you cascade them in an LNB they give a better overall noise performance and gain than the older lower gain devices.

Low noise temperature gets to a point where you can begin to see temperature variations as you move your dish. This background noise temp amongst other things sets the real background noise level of your system or System Noise Temperature.

If you have the equipment you can quite easily measure the noise output increase of your LNBF when you put your hand over the feedhorn becuase the LNBF noise temperature is lower than the physical temp of your hand.
 
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#11

frund

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#12
Does sound like April job.:D
 

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#13
Hitchcock said:
An LNB with a noise figure of 0.01 dB would also not give 200% signal strength (whatever that means), it would raise the C/N however over a normal Sky LNB (0.6 d:cool: by x 63, meaning the Sky minidish (45 cm) would behave like a 3.6 m dish with a normal Sky LNB.
The idea of dB in the signal path is to simplfy the equation of total losses by addition.

Once you remove the average 0.6dB from the rest of the losses (atmospheric noise, temperature, dish, cable, connectors and tuner), you find there isn't that much improvement anyway.
 

Llew

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#14
Hitchcock said:
I also asked a reputable LNB manufacturer once, SMW, and they told me they were using the best transistors (HEMT) available at the time, their top-perfoming LNB has a noise figure of 0.8 dB and it is the same noise figure they had back in 1995. With the arrival of the Invacom 0.3 dB back in 2002 I could finally see a better picture over what the SMW 0.8 dB offered, but not by very much. Going by the actual improvement I saw over the SMW, the Invacom is probably no better than 0.5 dB in reality.
Yes, I agree that the difference can be less than you would expect with a properly matched SMW LNB / dish combination.

I have done the same comparison with my SMW XL800B 0.8dB LNB and an Invacom 0.3db. to my SMW dish.

The SMW LNB can be expected to achieve maximum results using the same manufacturer's dish, and in my case using the Invacom with this dish doesn't improve the overall gain as much as I would have supposed considering the differences in noise figures. But of course being a universal twin LNB makes it much more convenient to use.

Llew
 

ouagadougou

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#15
Llew said:
in my case using the Invacom with this dish doesn't improve the overall gain as much as I would have supposed considering the differences in noise figures. Llew
Thats because Invacom and many of the others are misleading you when they quote a Noise Figure of 0.3dB which is purely for marketing purposes.

SMW are more accurate and honest when they quote 0.8dB.

If you went from a real 0.8dB NF LNB to a real 0.3dB NF LNB then you should see a sensitivity improvement of 4.4dB which is quite an improvement by any standards and is not far short of doubling the dish diameter. Clearly we dont get anywhere near that amount of improvement with these so called 0.3dB LNB's because the 0.3dB spec is fake.

The gain difference between LNB's is also very important and can contribut quite a lot to sensitivity improvement.
 

Hitchcock

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#16
ouagadougou said:
A Noise Figure of 0.8dB is still a realistic minimum at ku frequencies. The gain of successive transistor devices has improved over the years so that when you cascade them in an LNB they give a better overall noise performance and gain than the older lower gain devices.
Do you know exactly how they measure the noise? I'm curious because SMW do also make those X-Line (old Wideband type) LNBs, and for many years* they were quoted as having a noise figure of 0.6 dB (actually those are the ones I said appeared in 1995) whilst the newer WDL ones, and also the Quattro (= OMT + 2 WDLs), were only rated at 0.8 dB and when I asked SMW about this, they told me that they were in fact all of them (X-Line, WDL/Quattro) using the same transistors, it was just that the design of the WDL/Quattro was different or sth (he didn't really give me a good answer that day, herr M**** Kj******* :D).

* To my surprise their noise figure is now only quoted as typical 0.8 dB, whilst the WDL NF is still quoted as 0.8 dB as before, but the Quattro has gone up from 0.8 dB to 0.9 dB! So have their LNBs suddenly become poorer now (poorer manufacturing), or have they changed the way they measure the NF (yet again, to their disadvantage?) or what? :confused

ouagadougou said:
If you have the equipment you can quite easily measure the noise output increase of your LNBF when you put your hand over the feedhorn becuase the LNBF noise temperature is lower than the physical temp of your hand.
I wish I had the equipment, I would be bery keen to conduct this sort of experiment.

Channel Hopper said:
The idea of dB in the signal path is to simplfy the equation of total losses by addition.

Once you remove the average 0.6dB from the rest of the losses (atmospheric noise, temperature, dish, cable, connectors and tuner), you find there isn't that much improvement anyway.
Well, according to the formula I use (and ouagadougou too, as I can see from his last post), if you DO remove the noise (T = 0), then C/N suddenly becomes quite large ... :-hammer

(I do stand open for correction though, maybe I'm using an oversimplified formula.)


Spiney, do you know how much noise (in Kelvin) we could be talking about with one of those masers? Do you think it could ever be made available to us consumers? (Perhaps this is what the MOD or DOD use?)

An LNB with a genuine noise figure of just 0.1 (not 0.01) would really make a world of difference. For me and the Invacom I'm currently using it would be like quintupling (yes, that is 5 times) the area of my dish (more than doubling the diameter).
 

ouagadougou

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#17
Hitchcock said:
Do you know exactly how they measure the noise?

I wish I had the equipment, I would be bery keen to conduct this sort of experiment.

Spiney, do you know how much noise (in Kelvin) we could be talking about with one of those masers? Do you think it could ever be made available to us consumers? (Perhaps this is what the MOD or DOD use?)
Y Factor Measurements are the standard way to measure the Noise Temperature of a complete receiving system. You compare the noise output difference between a hot temperature like the ground and a cold part of the sky by moving your dish from one to the other and measuring the noise output change from your receiving system, there are a number of noise sources you can point your dish at to do these measurements. The bigger the difference in dB in this case the lower the noise temperature of your LNA/LNB. Because you know what the ground temp is and you know the difference in dB after this measurement you can then convert back and calculate your actual system noise temperature. When you have your system working well and with a big enough dish its quite easy to measure the noise output from the moon.

If you want to measure an amplifier on its own then a calibrated Noise Figure Meter is the easiest way to do this but you can build your own equipment that will do the same job for a lot less money. On my 2m dish I can quite easily see the movement on a normal analogue sat meter when I put my hand over the feedhorn this way my hand is hot and the sky temp is cold.

Maser amplifier noise temperatures depend on the type of cooling and the refridgerator temperature used but noise tmeperatures down to 3 or 4 kelvin are possible this equates to a noise figure of 0.04dB. The cooling systems are very complex and difficult for us to use at home.
 

kamaleon

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#18
My what an amazing thread me has started aiiiiiiiiiiiii

ali's indahouse
 

Hitchcock

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#19
Thanks for your detailed explanations, ouagadougou. This is all very interesting.

ouagadougou said:
Maser amplifier noise temperatures depend on the type of cooling and the refridgerator temperature used but noise temperatures down to 3 or 4 kelvin are possible this equates to a noise figure of 0.04dB. The cooling systems are very complex and difficult for us to use at home.
Ahh, an LNB with a noise figure of just 0.04 dB! :-rub That would be like the diameter of my dish (Invacom 0.5 dB LN:cool: shooting up from 1.8 m to 6.5 m!

Think of the demand for such an LNB in fringe areas where people are currently using dishes measuring 3 – 9 m! Those dish sizes would all come chrashing down to 0.8 – 2.5 m!
 

divibi

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#20
Hello!

Is Maser amplifier a kind of laser? Is it possible to buy DIY kits, just to have the simplest laser, then add a 'phase-change' PC cooling solution, for example and become the owner of an LNB of less than 0.1 dB ? Have such experiments been done before? Can it be made into a practical solution if only for a couple of hours a day, to make a hobby out of it?
 
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