It's Never Quiet Enough

When I moved to my current house I was excited to get my radios set up and start listening. The first time switched on my radios the S-meter was S9+. Yikes. It was time to go on a noise hunt. I followed the standard recommendation of shutting off all breakers in the house and turning them back on one at a time. I found the following items were generating noise at my house. Dealing with noise has been an ongoing battle.

A Creative Bluetooth speaker.
My 6 port USB charging block.
The LED lights in my kitchen ceiling fan.
An in-wall USB charging plug. I removed it and threw it in the trash.
Power supply for my CPAP machine.
The light dimmer switches in a few of my rooms.
My plasma television.

Cable Quality Matters

I recently moved my desktop computer from my desk to the top of a 6 foot bookcase next to my desk. Of course, I needed longer cables for my monitors. My main monitor has a DVI cable. My secondary monitor is a VGA monitor. I remembered I had a long VGA extension cable in my junk box downstairs. I should have left it there. The below pictures show the spectrum around the 20 meter band for no cable, the crappy cable, and a higher quality cable.

No VGA cable

Crappy VGA cable

Good VGA cable

This is a pretty skinny cable. More than likely not shielded. No ferrites on each end like the high quality cable.

Got this cable from Amazon.com. Got the picture from there too. This cable looks and feels higher quality.

Description from Amazon page: KabelDirekt SVGA, VGA Cable Male to Male Computer Monitor Cables (15 Feet) Shielded Copper VGA Video Cable

Watch Out For Laptop Power Supplies

Last year I was visiting my father. I took my RSP2pro and my laptop. I wanted to show him how cool SDRs were. I attached a 20 foot piece of wire to the antenna port, hooked up my laptop, plugged in the power supply and tuned to a known station in the AM Broadcast band. I got nothing but noise. I unplugged the power supply and was able to hear the station.

Over the past year I have been working at finding and dealing with noise sources in my house. A prime culprit for me has been my laptop power supply. Check out the below pictures.

Test One - AM Broadcast Band - Indoor Antenna

For this test the laptop and RSP2pro SDR were on my dining room table. The antenna was a 15 foot piece of wire draped across my family room.

SDR is tuned to 880 kHz. IF AGC is turned off.

Laptop: Battery Power

Laptop: Ac Adapter

Test Two - AM Broadcast Band - Outdoor Antenna

For this test the laptop and RSP2pro SDR were in my upstairs office near the window. The antenna was a 40 foot random end fed antenna between my office window and a 30 foot flagpole at the back of my garage.

SDR is tuned to 1130 kHz. IF AGC is turned off.

Laptop: Battery Power

Laptop: Ac Adapter

Test Three - 20 Meter Ham Band

SDR is tuned to 14.230 MHz. IF AGC is turned off.

Note: Y Scale has been changed to better show difference in noise floor.

Laptop: Battery Power

Laptop: Ac Adapter

Switching Power Supplies Are Noisy

We do not watch much TV at my house. The only reason I had cable is because my wife likes watching HGTV, the Hallmark Channel, and the show Say Yes to the Dress on TLC. I canceled my cable TV and signed up for a $20 per month streaming service that had those channels.

She also likes watching Good Morning America on ABC. So, I needed an antenna to receive over the air television transmissions. We live pretty close to New York City so I figured I did not need a fancy antenna. I bought a cheap active HD antenna from amazon.com. It worked OK but did not pull in the local ABC station. Bummer.

The antenna is in the attic. The USB powered inline amplifier is also in the attic. The wall wart switching power supply is plugged in a power strip next to my desk. It is connected to the inline amplifier with a USB extension cable.

Observation One - Indoor Antenna

When I first started in radio, some reference said "When starting out, just string a wire up indoors". That will work surprisingly well. Not quite true for my office.

I had my SDR tuned to a local station with a wire antenna strung haphazardly across my office. My intent for that particular listening session was not to hear distant DX. My intent was to learn how to use SDRuno better. When I tuned to 880 kHz, a local station, I was surprised by how crappy it sounded. When I turned off the power supply for the active HD television antenna, the station came in much nicer.

Test Conditions: 15 foot wire haphazardly strung around office. Laptop on battery power.

HD Antenna Wall Wart Off

HD Antenna Wall Wart On

Observation Two - Outdoor Antenna

For this test the laptop and RSP2pro SDR were in my upstairs office near the window. The antenna is a 40 foot random end fed antenna between my office window and a 30 foot flagpole at the back of my garage.

The spectrum captures show a marked difference at the low end of the BCB band. There was no audible difference in the quality of the tuned in station. R-Squared strikes again!

SDR is tuned to 820 kHz. IF AGC is turned off.

HD Antenna Wall Wart Off

HD Antenna Wall Wart On

Desktop PCs are Noisy Too

Observation One - Daughter's Desktop PC On/Off - Laptop & SDR Hooked to Outdoor Antenna

My laptop and SDR are by the window in my office, the middle room in my 2nd floor. The SDR is hooked to my 40 foot outdoor random end fed antenna. My daughter's desktop is in the next room at the back of my house.

Daughter's Desktop PC On

Screen shot with SDR and laptop in office and daughter's desktop PC turned on. This screen shot was taken the day after the below "On the hunt" pictures.

Daughter's Desktop PC Off

Screen shot with SDR and laptop in office and daughter's desktop PC turned on. This screen shot was taken the day after the below "On the hunt" pictures.

I unhooked the antenna and fastened a 3 foot piece of wire to the antenna connector and walked around the inside of my house. My daughter was playing video games with her friends so I did not go in her room. I would have found the problem quicker if I had gone in her room. In the rest of the house, the signal was strongest when I was near the window where the antenna enters the house. So, I decided the problem must be outside.

I grabbed a 10 foot piece of trim I had laying around and taped a wire to it, hooked it to my SDR and went for a walk in the yard. The signal seemed strongest in the back near the house. I walked around the some more and found it was strongest outside my daughter's room where she has her desktop PC. Sure enough, that was the culprit.

On the hunt.

The neighbors probably wondered what I was doing.

Daughter's Desktop PC On

Sense antenna right outside her window. Yikes!.

Daughter's Desktop PC Off

Sense antenna right outside her window. Much nicer.

Observation Two - My Desktop PC On/Off - Laptop & SDR Hooked to Outdoor Antenna

My laptop and SDR are by the window and are hooked to my 40 foot outdoor random end fed antenna. My desktop is 12 feet away from the SDR and laptop. I took a spectrum capture with the desktop off and desktop on.

I can't see any discernible difference in the 20 meter band, 14.000 MHz to 14.350 MHz. However, I do see thicker bands of garbage around 14.68, 14.80, 14.93, 15.06, 15.19, and 15.43 MHz.

My Desktop PC Off

My Desktop PC On

Picture Credits