LNB Performance vs Temperature

[cyberham]

Today the temperature is 48 F. My C-band LNBF hasn't performed as well as it this since last autumn.

Perhaps the improvement is due at least partially to the LNBF being colder which therefore might lower the thermal noise in its electronics. If this were true, would it be possible to have a refrigerated LNBF? You could literally plug the LNBF into AC power like a fridge or a freezer.

"Crazy ideas can turn into modern inventions". Red Green

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[comfortably_numb]

Red Green

He also said "If the women don't find you handsome, they should at least find you handy!"

 

[c-spand]

Today the temperature is 48 F. My C-band LNBF hasn't performed as well as it this since last autumn.

Perhaps the improvement is due at least partially to the LNBF being colder which therefore might lower the thermal noise in its electronics. If this were true, would it be possible to have a refrigerated LNBF? You could literally plug the LNBF into AC power like a fridge or a freezer.

"Crazy ideas can turn into modern inventions". Red Green

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Do you have a cover on it?

 

[907TECH]

We do not use LNB's in our commercial network, we use LNA's mostly. They sometimes see -60F or even colder, and maybe 90 in the summer. We don't see a noticeable difference in performance in winter but it may be measurable.

 

[cyberham]

Do you have a cover on it?

I only have an offset dish. So the LNBF/scalar is exposed but there is a plastic cap on the mouth of the feedhorn.

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[cyberham]

...They sometimes see -60F or even colder, and maybe 90 in the summer. We don't see a noticeable difference in performance in winter but it may be measurable.

That's a shame. But those are high quality commercial products and may therefore be superior to consumer products.

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[c-spand]

That's a shame. But those are high quality commercial products and may therefore be superior to consumer products.

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This can be cut to fit it.

 

[cyberham]

This can be cut to fit it.

Why would I do that?

 

[c-spand]

Why would I do that?

No worries.

 

[a33]

Perhaps the improvement is due at least partially to the LNBF being colder which therefore might lower the thermal noise in its electronics. If this were true, would it be possible to have a refrigerated LNBF?

I remember a broadcast by DrDish (in german), of Klaus Schumacher in Brazil cooling his LNB to get better reception of Astra at 19E in Brazil with his self-built 8 meter diameter antenna; in the analogue days.
Cooling with 'coldness spray' certainly did the job.
But I believe it was just done as a test, not as a permanent setup...

greetz,
A33

 

[c-spand]

I remember a broadcast by DrDish (in german), of Klaus Schumacher in Brazil cooling his LNB to get better reception of Astra at 19E in Brazil with his self-built 8 meter diameter antenna; in the analogue days.
Cooling with 'coldness spray' certainly did the job.
But I believe it was just done as a test, not as a permanent setup...

greetz,
A33

great info 33. thank you.

 

[Cham]

Cyber maybe you could add a peltier junction device to your LNB and cool it down even further?

 

[Brct203]

I have noticed better reception on the coldest days of the year (around 0F/-20C). My guess is that there's indeed a reduction of thermal noise in the LNBF, but also of thermal terrestrial noise when aiming for low satellites where I might be aiming through trees and other partial obstacles.

 

[comfortably_numb]

I, too, have noticed better reception in colder weather.

 

[mikekohl]

I, too, have noticed better reception in colder weather.

Enjoy the reception while ambient temperatures are lower than room temperature. For the summer, consider a plastic cover to minimize direct exposure of the metal outer portions of the LNBF, to stabilize frequency drift and give slight performance improvements.
A muffin fan would help during those summer months. Perhaps one of those new magic low cost air conditioners in an enclosed device would help even more. As far as winter performance, I doubt if major improvements would be worth the trouble in this situation. We used cryogenic cooling systems to get down to about 15 to 25 degrees Kelvin in military systems that I worked on in the 1970s, to improve parametric amplifier performance at 7-8 GHz. Cost was about $75,000. Kind of ironic when those same numbers could be had in a consumer C-band device a dozen years later for just a few dollars.

 

[Titanium]

You are noticing the seasonal reduced thermal noise from the earth and atmosphere. The LNB cavity temperature would need to be significantly lower to observe a change in the SNR.

 

[cyberham]

This morning on 97W C, I have two Mexican transponders that are 11.0 dB on my mini-BUD. This may be a record strength for this dish whether it's due to temperature or sheer power used by the tp. So even though this tp is DVB-S2 8PSK FEC 5/6, it is locked solidly all day long.

What is the range in transponder power used by different tps? Using this small dish, I find I can never lock anything on C from 87W, 89W or 95W. They don't exist as far as the small dish is concerned. Yet 91W, 97W and 99W have signals as stable as anything I receive on Ku.

 

[Titanium]

The capabilities of the satellite are typically found in the FCC filings or on the satellite operator's website information page.

Your measurement is signal over noise. The target signal may be constant but experience varying "noise" levels generated from spillover from the adjacent satellites carriers. Satellites also drift within their assigned box resulting in the potential for increased signal interaction. So many variables are introduced with an undersized reflector. Look at the spectrum displays received from adjacent satellites and sidelobes. You might find these frequencies are conflicting with the target service.

The link budget will determine the bandwidth and EIRP. The platform is a SSL 1300 and the transponders can be configured on demand. Can't find any recent filings that show the maximum power capability in the current 24 channel c-band configuration, but the platform is capable of combined 10kw.

 

[cyberham]

A spectrum analyzer is a tool that would be beneficial to look for possible interference sources. I do use the technique of motoring the dish to one side or the other in an attempt to evade interference. All of these different factors make it like fishing or chocolates: you never know what you're going to get.

 

[Brct203]

This morning on 97W C, I have two Mexican transponders that are 11.0 dB on my mini-BUD. This may be a record strength for this dish whether it's due to temperature or sheer power used by the tp. So even though this tp is DVB-S2 8PSK FEC 5/6, it is locked solidly all day long.

What is the range in transponder power used by different tps? Using this small dish, I find I can never lock anything on C from 87W, 89W or 95W. They don't exist as far as the small dish is concerned. Yet 91W, 97W and 99W have signals as stable as anything I receive on Ku.

not sure about their respective capabilities and how they would compare to other birds, but a few things to keep in mind:
- There's not much to lock on 87W and 89W in C-Band. There are some data transponders, but as far as TV/Radio, there are 2 active TPs on 87W (Bahamas TV and one radio TP) and one on 89W with CBS feeds (I think in 4:2:2).
- There's more content on 95W but mostly wild feeds, so that come and go. There's also the ABC feeds.
- I get about 14 dB on 87W, 15dB on 89W and 12 dB on 95W with a 10-footer in western CT.
- in comparison, Halifax NS is about 2dB lower than western CT on 95W and 89W, and 4dB lower on 87W

If not for the lower signal, the Bahamas mux might have been a reasonable target, but honnestly I think any of those would be really hard on a miniBUD considering your location. And you're not missing much ar all, to be fair.