It's interesting, isn't it, as long as you don't know what the CPU temperature is, it doesn't bother you. You just use it.
Google says:
"What is the maximum temperature a CPU can handle?
How hot should my CPU get? The safe temperature range for most CPUs is between 40–65°C (or 104–149°F). At the highest loads, your average CPU temps can go up to 80–85°C (176–185°F), but consider this the absolute limit. Sustained CPU temps above 80°C (176°F) can do long-term damage to the CPU and its silicon."
And my experience is that it depends on the modes in which I use it and how long (continuously). For me, the external heatsink is at room temperature, and the CPU temperature would be high for my usage if I hadn't done internal cooling.
I cool the outer rib with a 92x92x25mm silent fan.
I use it in FT4, FT8 and sstv mode, which use the CPU in continuous operation. One time I saw that I was close to 80C degrees, then I had no CPU cooling and I made a screenstream of the process I used.
When I noticed the higher temperature, I immediately stopped recording. I am currently cooling the CPU with a 50x50x10mm silent fan and heatsink. Thus, the maximum CPU temperature is around 40-50 degrees Celsius. I'm still using the first RPi4 and I changed the output FETs once because I was testing on battery and had no current limitation. I'm getting close to 4300 QSOs with these FETs I replaced and 6.3A current limiting at 12.5V with the IRFZ24N fets.
These are my experiences.
From the beginning, I constantly make sure that I am able to cool the heat-generating parts. I have been using the device since the release of the v3 alpha. (Nov 2023)
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Gyula HA3HZ
HA3HZ