Above quote reminded that I did some tests a while ago, after I bought an armor case for my Pi4, one of those big aluminium heat sinks.
I am not very good at putting tiny stickers on things, so installing the small heat pads were a challenge, and I had to use thicker ones I had for the ram, as the one supplied was to thin to connect with the heatsink.
The RPi 4 is in the attic, without a case mounted vertically. ADSB-CPU utilisation is at 70%.
At 10.30 I disconnected 80mm fan cooling Pi4/Airspy combo. The temps rose from 23 to 46 degrees, so nothing to worry about, at least not in winter.
I then swapped the RPis to the one with a heat sink, without any fan. The big heat sinks helps, even without a fan temps stay below 40 degrees C.
Then I switched on the 80mm fan again, and the temperature is almost as low as it was without the fan, but it seems without the case with the fan, they were a little lower.
The only caveat here is, that after swapped Pis again, the temperatures of the case and heatsink-free Pi were higher than they were at the start. Not sure what happened there, so maybe 80mm fan + heatsink are even better?
I guess the real test comes in the summer, when ambient temperatures in the attic are pretty high.
