Cooling SDR on LRO-H4(SETI Horn of Plenty) [hydrogen line radio telescope at LRO]. – astronomy.me.uk The Website of Lichfield Radio Astronomy Observatory (LRO)

[Andrew Thornett]

https://www.astronomy.me.uk/cooling-sdr-on-lro-h2scrt

This might be of interest to some hydrogen line observers.

Andy

[Ayushman Tripathi]

Hi Andrew,
Nice fix.

I've been thinking about something similar, but for a different use: using a small Peltier (TEC1-12706) to cool the LNA below ambient to bring its noise temperature down.

Some references on Peltier-cooling an LNA:
https://arxiv.org/pdf/0709.1840
https://science.nrao.edu/facilities/cdl/low-noise-amplifiers

https://www.mouser.com/c/thermal-management/thermoelectric-peltier-modules/

Cold side on the LNA, hot side on a heatsink + fan like yours.
The catch is condensation, going below ambient pulls dew/frost onto the cold side, so it'd need a sealed enclosure with desiccant.

Thanks.

[Andrew Thornett]

I have even bought the stuff for Peltier cooling but thought Id try a pair of fans first. Peltiers seem to use a lot of power so I am assuming I would to include some sort of temperature control, is that right? What would I use for that?

Sent from Outlook for Android

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[Ayushman Tripathi]

Hi Andrew,

Yes, you'd want temperature control. Peltiers draw a lot of power and don't like constant on/off cycling, so you don't want to just run it flat-out.

The simplest option is a cheap thermostat controller. You set a target temperature, it reads a probe, and it switches the Peltier on/off (or holds it) to maintain it.

I'll try to set this up soon and will share the setup pics.

Thanks.

[Adrian]

 "Peltiers draw a lot of power and don't like constant on/off cycling, so you don't want to just run it flat-out."   The only reason that you wouldn't want to run them flat out is that Peltiers are some of the lowest efficiency ways to attempt cooling anything and only the fact that there are no moving parts makes them even able to be considered. The reason you wouldn't want to run them "flat out" is due to their high power consumption but it's the only way to achieve maximal cooling and if power supply capacity is not an issue then it is OK.  The primary issue with constant cooling is the need to prevent condensation.  Electrically and thermally, Peltiers are designed to run at full rated current.
   Lastly the fact they don't like to be cycled on/off is strictly a nuanced statement. The reason this is conditionally true is due to thermal and not electrical properties. The Peltier semiconductor junctions and their coupled ceramic plates have differing coefficients of expansion. Repeated cycling of temperature extremes as with full on and off cycling tends to form stress cracks in the junctions and detachment of the ceramic plates causing premature failures. However, cycling with PWM at higher hundreds or higher frequencies that regulate temperatures gradually and allow thermal inertia to smooth mechanical stress is adequate. Also regulation with linear constant current regulation is also possible with feedback regulation of power for temperature control.

Adrian

[Adrian]

I'm sure this is way more than anyone is interested in but can serve as a reference point for a comprehensive view of just how advanced Peltier temperature control can  become.

https://www.renesas.com/en/document/apn/rx23e-group-example-thermoelectric-peltier-controller-application-notes?r=1473661

Adrian