Odd visual artifacts on one Mac, but not on another

m5kvk

https://garethhowell.com/wp/wp-content/uploads/2026/07/IMG_5398.mov

The video is of SmartSDR for Mac running on my MacBook and on my Mac Mini. Both are running SmartSDR for Mac and connected to my remote 6400 tuned to 80m with the same Display settings.

As you can see, the display on the Mac Mini has spikes at a regular rate.

The only difference is that the Mac Mini uses an Ethernet connection whereas the macBook is using WiFi.

As an extra check, I looked at the same setup on the PC in the remote shack. There's nothing there, so it's not coming over the air.

I've no idea what's causing the spikes. Any suggestions?

Erik Carling EI4KF

Not related to cause but effect: are you using screened CAT8 ethernet cable?

Related to cause: have you tried turning off each of all likely sources of pulse noise in your house to try and identify the culprit?

m5kvk

Good suggestions, Erik.

To the first, no. My local shack (remember, the radio is remote) is down the bottom of the garden on a "TT" (i.e. supplied by Live and Neutral with local Earth) supply. Plus, the supply has a very good filter on it. Using an oscilloscope and VNA I can see nothing induced or transmitted on the mains supply.

That's not to say that there are no spikes on the supply, but they don't show up on anything else. However, you are right: the other distinguishing feature is that the Mac Mini is mains powered, whereas the MacBook is battery powered.

Further investigation shows that the interference spans the range 500kHz to 6MHz. Interestingly, the result varies depending on whether SmartSDR is set to "80m" or "Gen". On the latter, there is no interference.

K3CDY

This is very interesting. On the offending Mac, I notice that the spikes on the FFT display are not being captured in the waterfall below. If this were truly some sort of external interference, you would see those spikes painted on the waterfall, and creep down - and that’s not happening.

To me, this smells more like a software glitch.

Have you tried an app de/re-install?

m5kvk

Hi Bill

Since I posted, SmartSDR for Mac updated itself and the artifacts remain. I think the reason they aren't also on the waterfall is the update rate. If I increase it, the artifacts do appear as a white horizontal line across the screen. They aren't affecting the audio though.

Very odd.

m5kvk

Update: I was able to activate the WiFi interface and switch to using that. No difference.