studentkra

Most switching power supplies change the frequency of the converter depending on the temperature. Not much, but enough to notice it at the waterfall. If it is not possible to disconnect the power source you are testing from the mains, simply heat it up a little with a hair dryer and look at the signal on the waterfall

@IK8SUT , I don't have a diagram. This is a classic power supply consisting of a step-down transformer, a diode bridge and a 1084 linear stabilizer.

I used a toroidal transformer from a BBK household amplifier. The secondary windings of this transformer had too much voltage, so I simply wound two windings on top with a thick stranded wire of 12 and 5 volts. I used four diode bridges to power three 5 volt channels and one 12 volt channel. After the diode bridges, I installed electrolytic capacitors and linear stabilizers. One 7812 and three 1084. (I bought some MP1584 high frequency converters. I'll test them for noise later). After linear converters, I used filters from inductors and capacitors. I'll attach some photos.

If anyone is interested, I use a linear transformer power supply. I have three SDR receivers. One KiwiSDR, one FlydogSDR and one RSP1A running Orange Pi4 lts. I also use a Microtik LTE router, an ethernet switch, and active loop antenna and a downconverter. Depending on user activity, the total electricity consumption is 60 watts per hour.