I made a similar setup with a power supply of 5.2 V / 2.0 A. But with a Rpi3B+. Due to the load of the Rpi3B+ and the RTL2832 dongle, the voltage dropped to 4.99 V with a current to the dongle of 0.25 A. Due to its components was also expected that the Rpi3B+ would make a heavier claim on the supply and that therefore the manufacturers have increased the supply voltage by 0.2 volts. I think it will be financially more advantageous for the manufacturer than a heavier supply. So for an economical Pi1, a 5.2 V supply is too much of the good ... Joop.
Little differences between the nominal power and the actual voltage supplied to dongles are not that significant and directly related to heat. Let's suppose a difference of 0.5V on a current of 0.25A....we are talking about 125 mW more or less to be dissipated...
The definitive solution to heat problem (the passive way), if you're looking for something sturdy, working on the long term, without cooling fans...
Yes, it isn't suitable for a direct connection to Rpi (it inhibits connection to the free ports also), a short Usb cable is required...but I can tell you that after hours of service you barely can feel is working!
Nothing, I've just made sure the contact surface was clean and polished (I had to saw a big cpu heatsink in three pieces).
CPU fans are brushless motors, usually they have a very low EMI rate and chances to affect an RF digital signal are really close to zero.
This is what I ended up with so for for a sealed passive cooling solution for outdoor use. Dan started the idea with his roof top unit. I have yet to drill hole for the wires. I going to use RTV to seal the gaps, likely the red high temperature as that held up for 20 years in the engine compartment of the aircraft. Case will be mounted under a $100 USD 100W solar panel with a $100 USD deep cycle marine battery. CASE AND HEATSINKS https://www.amazon.com/gp/product/B01HMCYV80/ $22 USD https://www.amazon.com/gp/product/B001A1VE8A/ $22 USD https://www.amazon.com/gp/product/B01H8L4EM8/ $8 USD https://www.amazon.com/dp/B07D15MDXH/ $11 USD USB CABLES https://www.amazon.com/gp/product/B01GA1GKYW/ $9 USD THERMAL STICKY STUFF https://www.amazon.com/gp/product/B075F37SQG/ $17 USD 25M thermal tape https://www.amazon.com/GENNEL-Conductive-Silicone-Adhesive-Compound/dp/B072MSXHJD/ $5 USD
