Active cooling for better noise figure

[WesTheTinkerer]

I was thinking about removing the cover of a Ku LNB to expose the aluminum housing
and then placing some dry ice on it or wrapping some fine copper tubing around it and
circulating some ice water through it. It may throw off the L.O. stability too much so that
any improvement in S/N would be wasted. Any thoughts? Has anyone tried this?

 

[Lak7]

Has anyone tried this?

There is a video of a guy using a can of "Air" to freeze his LNB for improved stability / signal - not very practical.

A bigger Dish is always a good place to start.

 

[WesTheTinkerer]

Yes, I know but that is not as interesting of a discussion. I imagine standing at your dish spraying down your LNBF while trying to watch TV is impractical. Run some rubber tubing from the copper coil down to a reservoir with a windshield washer pump or just use a Peltier cooler. Anyhow I live in a historic district and if I had a ten footer in my back yard the Historical Society would tar and feather me! My neighborhood became a historical district after I moved here 41 years ago. I'm surprised I get away with as much as I do now.

 

[Lak7]

something to consider.....
http://www.dishcamo.com/dishcamo.htm

 

[Lak7]

or take one of these apart....
http://www.target.com/p/igloo-breez...964465&LID=PA&ci_src=17588969&ci_sku=13964465

 

[SatelliteAV]

A story in TeleSatellite magazine many years ago about a hobbyist in South America receiving out of footprint Austra / Hotbird signals with a monster dish and chilled LNB. Dr. dish has some interesting experiments on some European forums.

There also have been discussions through the years here on the forum about chilling the LNB. http://www.satelliteguys.us/threads/154409-Lowering-LNB-Temperature

 

[WesTheTinkerer]

something to consider.....
http://www.dishcamo.com/dishcamo.htm

Those look really nice. I suppose you'd need two, one for spring/summer, and one for fall/winter.
I have already thought about painting it.

 

[WesTheTinkerer]

or take one of these apart....
http://www.target.com/p/igloo-breez...964465&LID=PA&ci_src=17588969&ci_sku=13964465

I can buy surplus peltier coolers here http://www.goldmine-elec-products.com/prodinfo.asp?number=G19077 for $2.95 and use junk fans from fried PC PSUs.

 

[WesTheTinkerer]

A story in TeleSatellite magazine many years ago about a hobbyist in South America receiving out of footprint Austra / Hotbird signals with a monster dish and chilled LNB. Dr. dish has some interesting experiments on some European forums.

There also have been discussions through the years here on the forum about chilling the LNB. http://www.satelliteguys.us/threads/154409-Lowering-LNB-Temperature

I know that it will work and I know how to do it. The problem is that inside the LNB housing there is an LNA which is really what needs to be cooled, and an LNB with an oscillator which needs to be maintained at a constant temperature to remain at a "stable" frequency. Since they are both in the same housing you cool both of them. If you look at the spec sheets of some LNBFs the stability of the L.O. is stated as + or - so many Hertz within a temperature range. Stability drops because an oscillator's frequency will drift with temperature. For stability the crystals of crystal controlled oscillators would be put in temperature controlled ovens so their frequency would not drift (as much) Therein lies the conundrum. I just wondered if any body had done it and got any benefit from it. Thanks for directing me to the old thread I will definitely take a look. So far everyone here has made me feel welcome. Thanks guys.

Wes

 

[SatelliteAV]

You might consider starting with a PLL LNBF like the GEOSATpro SL1PLL to minimize the DRO temperature drift.

 

[WesTheTinkerer]

You might consider starting with a PLL LNBF like the GEOSATpro SL1PLL to minimize the DRO temperature drift.

I am using an Avenger PLL with a noise figure of .1db and frequency drift of +/-300KHz. I believe the one you refer to has a noise figure of .5db if I remember correctly from when I was shopping for my first LNBF. Yes it does I just checked. I knew my dish was too small so I wanted to get the most out of it. I did get about 50 channels on 97W. Now I have a 99cmx90cm offset dish. I did buy a microHD from you. Great receiver by the way.

 

[primestar31]

That .1 noise figure is BALONEY!

It's a good lnb, but no way it's actually getting that noise figure, even so noise figure is NOT everything! I have both the Avenger AND the SatAV SL1PLL, and the SatAV one outperforms the Avenger hands down. There's a dealer on Ebay who is selling the SL1PLL shipped FREE, and I've even bought yet another from him, and he took a "make offer" a $1.50 cheaper.

So unless you truly need a universal lnb, the SatAV one may work better for you.

 

[danristheman]

Is this on ku band or C band? Do you get better Quality in the winter time cause of cold temperatures?

Dan Rose

 

[WesTheTinkerer]

That .1 noise figure is BALONEY!

Primestar, from what I have read you are absolutely right! The avenger is probably more like .5db. I don't even know if I can trust any of the specs! But you live and learn. There is no substitute for experience. It had free shipping. I wish I had the money to buy another brand new dish but I'll just have to wait while I save my pennies. I bought the WSI dish and it's okay for the $98 bucks I paid for it but it is not as nice as the Geosat pro dishes, going to buy one of those next.

 

[WesTheTinkerer]

Is this on ku band or C band? Do you get better Quality in the winter time cause of cold temperatures?

Dan Rose

Dan, it's Ku. It would be easier on C-band on a system with a separate lna and lnb. Dang I can't spell! Thank you spell check and Google. All of this is really just academic anyway right. Years ago when LNAs had higher noise temps it would make a difference but now it would be a drop in the bucket. Minimizing the losses elsewhere would probably give you what you would gain by hacking the Ku LNBF or the LNA on a C-band dish. Just increasing the size of the dish by 10% would do more.

 

[danristheman]

I didn't know if the cold played a factor in signal quality. I use on my 1 meter dish with superdish FSS lnb I got on 97w RT in at 90% quality. would the cold play a factor in a superdish FSS lnb? Also getting prepared for winter.

Dan Rose

 

[Blindowl1234]

Dan, It's 23 here this morning and on my c band I get a little better signal on these cold mornings. I think the sun causes the panels on my dish to flex a bit when it's warmer. Either way I notice a slight improvement when it's cold. With the lnb the temps don't matter..seems to work the same hot or cold. My dish seems to have a mind of its own anyway though lol.

 

[WesTheTinkerer]

I think Blindowl is right. All of my Ku lnbs have black plastic covers though which makes me wonder.

 

[WesTheTinkerer]

Dan, I really don't think it matters. I think I should have just kept my mouth shut. No, I'm quite sure I should have.

 

[SatelliteAV]

It all adds up... LNB chilling will improve performance!

• Atmospheric conditions
• Appropriate sized dish with surface accuracy and efficiency
• Correct matching feedhorn and placement
• Correct scaler
• LNBF with stability and performance based on a balance of gain, amplification with minimal noise
• Minimal connections and coax length
• Quality and appropriate connectors and coax
• Proper coax routing and connector installation
• Quality receiver with sensitive tuner that is optimized with supporting PCB build, chipsets, demod processing and firmware routines

You are correct... Black plastic (either cases or enclosures) do not improve LNB(f) performance. Black absorbs heat and does not promote cooling of the electronics.