Is it benefitial to ensure that low noise amplifier and filter (LNA) for hydrogen line observing is at a constant temperature?

Andrew Thornett:

I could see potential benefit for having LNA at constant temperature. The easiest way to achieve that is to cool it below any likely outside temperature – avoiding need for heater at well. Plus heating adds noise.

But cooling below ambient leads to condensation hence need to dehumidify. 

You can tell I am just thinking on my feet here….probably should think it out properly then post a single post….

Nevertheless, Alex gave me some advice – he didn’t use these words but I interpreted his advice as follows – apologies, Alex, if I have misunderstood you:

A radio telescope system is only as good as its weakest link. Therefore, there is no point is having a wonderful cooled LNA when the dish/coax/waveguide/SDR/etc. Is not optimised to the same level.

Even then, a poor radio environment, trees, or other sources of obstruction or reflection of radio signals, or other sources of RFI, unstable power supplies, even cloud and poor weather/too many airplanes/etc. may limit how far a system can be optimised.

Alex Pettit:

As the Thermal Gain Coefficient of the  Nooelec SAWbird H1+ LNA (the most popular low noise amplifier and RF filter used for hydrogen line observing by amateurs) is only -0.1 dB gain decrease per + 10 degree Celsuis change in temperature, it is a only a minor part of system drift sources. 

Exec Summary : There Are Much Bigger Fish To Fry – see list below!

Potential Small Radio Telescope Background Drift/Shift Sources:
1. Ground Noise Spill-over
2. Outside Temperature Variation
3. Sky Transparency Changes
4. Sun Blackbody Radiation in Antenna Beam Pattern
5. Sun reflection off roofs / buildings / trees
6. Radio Frequency Interference ( LAN Blocking )
7. Radio frequency Connection Thermal Expansion Ohmic Changes
8. Thermal LNA Gain Changes
9. Thermal SDR Filter Shape Changes
10. Sunlight Refraction off Clouds