Cheap switching power supplies are too noisy for ham radio use

hi there this video is about these cheap switching power supplies by an Amazon and other places the great value for money but they are a little too noisy sometimes for use in ham radio and I'll show you why this one I modified with this little volt display it's just soldered under the board with the wire coming up quite convenient great motto recommended now in an effort to tame the noise a little bit I've tried to use this big chunk in toroid it's not really doing much but let's go over to my icon and the waterfall display you can see here several bands of noise all this noise is in fact coming from my power supply and I can prove it a couple different ways but let's look at these bands of noise a little bit first so right now I'm tuned to 2 1 4 165 and you can see this band of noise and we turn up the volume a little that's pretty substantial noise at an s4 right now for this this particular spot okay now remember 163 tuned down a little bit here to this band of noise 136 that's about 27 kilohertz ish there pretty wide so 27 and a half kilohertz ish frequency difference in between and you'll notice they happen over and over and over and over again the Hat on this radio with this power supply it's every band everywhere 27 kill Urtz turn that down because that's annoying now I've hooked up my oscilloscope sorry for the shaky cam and I haven't hooked up to the output of the power supply to show what's going on it's just a little blurry at the moment but this is zoomed in on the DC waveform coming out and if I adjust the trigger just right you can see a little bit of an extra blip sometimes it's a little faint at the moment because first I'm recording this guy right there that zigzag that's the one that's the impulse we're looking for now unfortunately probably have to cut this to try and make note right there you can see another little blip all right about there if I turn my time cursors on again so the difference between this line and this line is about eighteen point three microseconds and if you do the one over on that that's 54 kilohertz the chapter to be roughly pretty close to double 27.5 kilohertz so that is definitely our culprit this little bit extra doesn't seem to be doing much at least not that I can find now let's actually empirically prove or yeah more empirically prove that this is what the issue is by turning off the radio unplug it and I have here a nice lipo battery of the correct voltage that can plug in there we go power back on the radio and oh wait they're still there why is that because the power supply is still on if I you throw the switch to turn it off notice that's starting to fall and all the zigzag lines fade and just disappear now it's nice and quiet it's running off the battery it's nice and quiet much better than before and so that's the the final proof that these guys are noisy I've been using it I'm gonna keep using it for a little while until I find something to replace it I've made plenty of QSOs a lot of ft8 contacts with it how it is there's plenty of room between the spikes of noise so you operate but sometimes it lands right on top of somebody you want to talk to you and it's really annoying not sure what to do about it if I want to keep using this guy but I think this may be relegated to battery charging and things like that and not run my ham radios in the near future so thanks for watching and that's all I got for you

Channel: The Killer Spud

Views: 5,117

Rating: 4.8024693 out of 5

Keywords: Amateur radio

Id: 1pcFojqaka8

Length: 5min 13sec (313 seconds)

Published: Sun May 17 2020