Freezing an LNB?

[SatSearcher]

Just been reading on another forum about the effects on LNB's when they're cooled or even frozen, seems some members are getting very good results when spraying the LNB with freeze spray! Anybody got opinions on this?

[ouagadougou]

I havent tried freeze spray but cooling does work because you lower the physical temperature of the whole device and so the noise temperature/noise floor and sensitivity is lowered as well.

You can buy specially made cooling chambers that use dry ice or gas to cool as low as possible but the main risk is wether or not the original LNB housing can handle the very cold temperatures encountered or even if it will fit the cooling chamber.

We used to cool all the LNA's in Sat Earth Stations but that was a while ago.

Cooling chambers are available for people who try amatuer radio astronomy and they arent that expensive.

Not an easy task this one but could be worth it for the real enthusiast. Just wish I wasnt stuck in Africa as I have a chamber at home waiting to be tried out !!

Cheers.

[SatSearcher]

Sounds an interesting challenge! I know there's no substitute for a bigger dish, but this could be an alternative for people who either can't afford bigger dishes or don't have room for one. Think i might just test out freeze spray for now, see what results it gives. Just worrying a bit over whether it will damage the LNB at all?

[ouagadougou]

There is a chance you could damage the LNB because the LNB housings arent designed to be forced cooled like this. Also the rapid cooling then warming from a freeze spray may be too much for the LNB seals.

You wont know for sure until you try.

The biggest problem with the cooling chambers is the size and weight and the fact that they need to go at the focus of a prime focus dish or on the supoort arm for an offset dish so there are some mechanical problems to solve.

[satwyn]

have a look at dr dish it does work or you could move to the north pole

[xanadu]

Freezing an LNB below the manufacturers operating specification can also cause problems with frequency drifting as the LNB has been setup in the factory to work within a specific temperature range.

In theory super cooling will eliminate thermal noise and give a slight improvement to performance.

[Detlef]

have a look at dr dish it does work . . . .
I guess you are referring to this old German guy in Brazil that can get the ana1ogue channels from Astra 19.2E on a monster dish. He cannot quite get any of the digital channels though, so has enlisted the help of an LNB manufacturer and they have tried a cooled LNB. At the current rate of slippage of the ana1ogue switch off, he will probably suc***b before it happens :D

There are peltier effect coolers, a sort of reverse thermocouple (see: _http://en.wikipedia.org/wiki/Thermoelectric_cooling ) where one side of a semiconducting sandwich gets cool as the other side gets hot, that may be a possibility.

zanadu makes a very valid point. In the early days I had an LNB that was worse in cold weather. It turned out that the case distortion was causing the LO to drop frequency by more than the AFC could handle.