Which PoE for RPi4 and Airspy Mini?

I’ve done my own stress testing.

First you can see the temperature with the default settings of the PoE hat, this is from the start of the graph to around 08:40.

Then I switched to have the fan on at full speed continually until 11:40

Then I changed the fan configuration to be the same as @jonhawkes2030:

dtparam=poe_fan_temp0=40000,poe_fan_temp1=45000

Translated, this means turn the fan on at the lower of the two speeds at 40°C and then go faster at 45°C.

I ran the same stress command until 13:00 (with a very quick dip when I had to restart the test)

stress -c 8 -t 1999

You can just see that at 10:40 my central heating kicked in and the shack temperature rose by ~1°C.
While the stress test was running, the temperature was around 45°C to 46°C but never higher. It was around the same as the Pi at idle without any cooling.

htop

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They also used just the heat sink alone, and that only lowered the temperature just a few degrees.

It was one they sell for their cases, which is not that high but with a footprint way larger than the cpu. Maybe it just is a bad design, and smaller heat sink with the fan directly attached would perform better.

Still, I‘d say any airflow will be enough to keep temps in check.

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@LawrenceHill,

I did look at that post, however, it was on a commercial site advertising their own fan.
It is not clear if they used heatsink tape or adhesive.
Their tests got a lot hotter than mine. I did not get hotter than 45C. I may not have used the same application.

For airspy and/or attic use, a fan is clearly going to help. I think a fan and heatsink even helped my RPI2 years ago when trying the airspy in the early days.

The heat sink they used was also one their own and uses thermal tape, pre-applied.

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