Tracking the Elusive SMPS

20 Feb 2022


KiwiSDR waterfall with normal AC power

AC Off

KiwiSDR waterfall with (most) AC power off

In starting the long, slow climb to the heights of the SNR mountain, one of the key activities is identifying and mitigating “self-noise”, or noise coming from devices in your own shack/household/installation.

In my case, this is a difficult proposition, since other members of the household enjoy their electricity and get upset when it is removed. Nonetheless, an opportuntity arose for a quick check today, and the results are shown above.

The results are a bit difficult to read, but a broad band of hash around 20 MHz seems to disappear, yet some weaker ones pop up elsewhere. I’m thinking that some image processing techniques like the astronomers use, like “subtracting” one image from another might be helpful here.

Some more work needs to be done to find a way allow the Kiwi to still be present on the (somewhat extensive) household network (comprising two routers, half a dozen switches, three WiFi access points) while shutting most of it down.

Another technique, which should also be applied, is to use a “noise receiver” with a portable antenna and wander around the facility looking for hot spots. I have a new, battery-powered Icom IC-705 that might be perfect for this purpose, I just need to figure out what kind of strange-looking antenna might be effective for the lower portions of HF.