Noise Sources in the Shack

Efforts to hear weak signals are hampered by noise. Most often, noise outside of the home cannot be mitigated. However, noise on your own property can often be eliminated. The purpose of this post is to document my Noisy Fox Hunting efforts.

04/4/2025 Broadband noise on 10 M

For some time, I've been seeing a band of noise wandering through my spectrum display on 10 M. I finally took time to track it down. My shack has switched outlets, one on the north and one one the south. These are controlled by voice commands. This is cool because I can say, "Hey, Google, turn radio shack off." The outlets are on the north and south wall. The north wall is where all the ham gear is. When I turn the north side off, everything goes down except the radio and the computer.

When I turned the north side off, the noise you see in the display went away. I traced it to my main ASUS display. It turns out that, when the screen is active, the noise is present. If the screen goes dark, via a power down or screen saver timeout, the noise goes away. So, at least I know what it is! I don't know if the noise is from radiation from the active display but I suspect that is the case.

I have another ASUS monitor mounted above that, so far as I know, does not exhibit this problem.

Problems like this are Buying Opportunities to upgrade to a larger monitor. The monitor size is you shack is a function of your age.

03/25/2025 Broadband noise on 20 M

For a day or so, there has been a broadband noise on 20 M and other bands. I finally took my QODOSEN DX-286 around the house. I could hear the noise throughout the house so I went outside on my rear deck. The noise decreased. As I approached the back door of the garage, it increased.

Fig 1. QODOSEN DX-286

Wandering around in the shop, the noise increased as I approached a power strip on my bench. When the strip was turned off, the noise I was hearing on the AM radio at 14012 KHz went away. Figure 3 shows the noise with  the strip on. Figure 4 shows the ICOM display with the strip OFF.

Fig 2. The Dirty Power Strip in the Shop

Fig 3. Noise on 20M Band - Power Strip ON

Fig 4. Noise on 20M Band - Power Strip OFF

Conclusion

In Figure 3 and 4, the frequency display spanned 80 KHz. In Figure 4, when I reduced the span to 16 KHz, the remaining noise was spread out enough that it could not be seen. It appeared to be a modulated signal. It is steady frequency-controlled. Noise from USB sources is not frequency stable.

The literature suggests that power strips with built-USB ports are known to generate noise. Given that evidence, I intend to search my entire house for noisy USB supplies and devices. The hunt continues.

References:

1. https://www.perplexity.ai/search/cfcdda66-337a-4355-b018-625c37e8f32a
   
2. https://kl7aa.org/usb-interference-fun-on-hf/
   
3. https://www.arrl.org/power-line-noise
   
4. ARRL, "The ARRL RFI Book," First Edition, Edited by Ed Hare W1RFI, c1998

03/25/2025 Broadband noise on 20M (Douk Audio ST-01/ ST-01 PRO)

Stay Tuned!