Lowering LNB Temperature

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nelson61

nelson61

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Has anyone here experimented with lowering the lnb temp with a thermoelectric cooler to improve signal strength? Thinking of running a similar test.

I was watching Klaus Schumacher's videos of his 8 meter antenna with rotating lnbs on Utube and saw that sticking a thermoelectric cooler on the lnb should pick up 1 dBW and maybe 2. That's like adding something like 50 percent to the dish area.
 
Inno

Inno

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In that case those of us in the Great White North should have signals that are off the scale in the middle of winter, this is not really the case in my experience. I haven't really noticed any appreciable gain in signal strength summer to winter.
 
T

tvropro

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When winter comes the earths noise floor in Kelvin (K) decreases, so this does help. Back in the day when LNB's had high noise temps (80-120) you could notice a reduction in sparkles in the winter. My first dish a 10 foot Tee Comm (Alpha -10) with a 65 degree gasfet LNB did show improvement when it got cold. With LNB's noise temps lower than the noise temp of the dish and satellites much more powerful there don't seem to be much change on our end like years ago. I don't see you gaining much or anything trying to lower the noise temp further. Money and time would be better spent getting a larger dish.
 
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Mr Tony

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heck I have a LNB that shorts out when it gets cold out....when the temp is +10F or below the LNB wont work
 
nelson61

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Here's the links showing their test data and the 8 meter dish. This guy has to be the "God" of amateur dish designers.

8 meter antenna video

[ame=http://www.youtube.com/watch?v=Q0JFP7NFx3s]YouTube - Astra in Brazil - Klaus Schumacher 8M Dish : Part 1 of 2[/ame]


Cooling lnb video

[ame=http://www.youtube.com/watch?v=EtO1H0jhrzQ&feature=related]YouTube - Cooling of LNB to improve reception performance[/ame]
 
Larry1

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The idea is good, but the whole picture of all the noise sources should be looked at to get the maximum lowest signal to noise ratio. Better cable from the LNBF to the receiver or a better tuner in the receiver could do just as much for lowering the noise as cooling the LNBF. (maybe, have not tried this myself) Also I have always woundered if you ran a separate power cable to the LNBF so it would not be on the same cable as the signal could you get a better signal? There must be some losses at the point where the power is inserted on the cable and again where it is taken off the cable, after all every circuit in the signal flow does add noise to the siganl. In the end, the most lost would be due to weather, so a larger, better quality dish is the ultimate solution. More, better signal to start off with before any losses or noise are introduced.
 
Inno

Inno

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Hmmm, that is interesting. I guess in the case of a distant satellite with marginal signal, that might be all you'd need. In a case like Hispasat from North America.
 
14karat

14karat

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Y,know... after reading all of this the only thing that keeps coming to my mind is pretty basic:
I think if I had a 26 foot dish I probably wouldn't be worried much about low quality signals... :)
 
T

tvropro

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Y,know... after reading all of this the only thing that keeps coming to my mind is pretty basic:
I think if I had a 26 foot dish I probably wouldn't be worried much about low quality signals... :)

Bigger is always better :D
 
B.J.

B.J.

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While I don't doubt that cooling the lnb could help a bit, one thing that hasn't been mentioned is that when the temperature drifts much from "normal" ambient temperatures, most of the lnbs we use will drift in freq. I had one KUL1 lnbf that drifted 5 MHz off freq when the temperature got down to mild winter temperatures. Other low cost Cal-Amp and Norsat LNBs would drift up to a couple MHz. I now have a couple more stable lnbs, so I'll be interested in how much they drift this winter, but the bottom line is that all these lnbs are rated over a relatively narrow temperature range.

Similar to the ICE example above, I once had an LNB that when the temperature got down into the 10-15 deg F range, it would develop an internal oscillation that you could see going across the band. As the temp dropped each night and went through that 15-10 deg range, you could see the birdie signal destroy one channel at a time. I had to put an X-10 switch on the receiver, and when the oscillations started, I'd switch it off for a few seconds, then turn it back on, and it would be OK. Once the temp got below 10, it was OK.

I have generally had better reception in winter, but I attribute that to having no leaves on the trees.
 
T

tvropro

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While I don't doubt that cooling the lnb could help a bit, one thing that hasn't been mentioned is that when the temperature drifts much from "normal" ambient temperatures, most of the lnbs we use will drift in freq. I had one KUL1 lnbf that drifted 5 MHz off freq when the temperature got down to mild winter temperatures. Other low cost Cal-Amp and Norsat LNBs would drift up to a couple MHz. I now have a couple more stable lnbs, so I'll be interested in how much they drift this winter, but the bottom line is that all these lnbs are rated over a relatively narrow temperature range.

Similar to the ICE example above, I once had an LNB that when the temperature got down into the 10-15 deg F range, it would develop an internal oscillation that you could see going across the band. As the temp dropped each night and went through that 15-10 deg range, you could see the birdie signal destroy one channel at a time. I had to put an X-10 switch on the receiver, and when the oscillations started, I'd switch it off for a few seconds, then turn it back on, and it would be OK. Once the temp got below 10, it was OK.

I have generally had better reception in winter, but I attribute that to having no leaves on the trees.

My 1989 vintage 40 deg Cal Amp LNB has always worked perfect in the hottest 110 degree summers to the coldest below zero winters. When I bought it it was the same model being used by cable headends it cost me over $200 but has been well worth it. Something to be said for good old quality :)
 
Mr.Arizona

Mr.Arizona

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...not sure if they mentioned it in the videos. But he is at least 3000 miles away from the edge of the footprint.
I was reading about it in the German version and was very impressed.

Just my 2 cents...
 
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