RF Small Signal Amplifiers and Cooling

[dnyberg2]

I know that in the pursuit of low noise amplifiers, the cooler the better, generally speaking. But when does it make sense to try and go through the work required to cool an amp? One of my passions is radio astronomy. I have a good collection of LNA's around of various types and an eight foot dish to play with. Some of my amps are, run of the mill, small signal amps with SMA connectors in blocks of metal from surplus equipment. I am working up to the point of being able to determine the noise factor of these AMP's and was wondering, even if I knew what an AMP's NF is, how can I tell how much improvement is possible with even moderate cooling? Is the effort worth it? For instance, during the day it gets quite hot outside up here in the mountains of CA where I live. What would be the hypothetical advantage or improvement in RF AMP noise if I put the amp in a small freezer? Thanks in advance.

 

[nsaspook]

Most of the stuff I saw for Satcom ground stations was cooled to about 80K. To get lower than that you needed a vacuum cryogenic Helium cooler. You might try a dry-ice cooler.
http://www.setileague.org/articles/cooling.htm

 

[the_emi_guy]

Keep in mind that amps often have a fairly limited operation temperature range, such as -40C to 85C. Cooling from 25C down to -40C will only buy you about 0.8dB noise reduction.