I Audited the RF Noise in my House

The largest problem facing analog AM broadcasting (and digital Medium Frequency and High Frequency broadcasting) is RF Noise.

Like most people, I have many modern conveniences that make my life easier than previous generations; electric lights, central heat and air conditioning, appliances like vacuum cleaners, microwave ovens, and whatnot. I enjoy the wireless internet, have an LED TV, use LED light bulbs, and get free electricity from my photovoltaic solar system. These devices can contribute to the high levels of RF noise found in most buildings. RF Noise which is the bain of AM broadcasting. Digital modulation schemes use variations in amplitude to transmit data bits. They are not immune to RF noise, they simply mask it better until they don’t.

I thought it would be interesting to isolate the various noise generators that may be present.

To make measurements, I used the Siglent SVA-1032X spectrum analyzer. This unit has a noise floor of -140 dB. My methodology is to turn everything off except the Device Under Test. Set the spectrum analyzer up for a wide band sweep, then narrow the bandwidth on any detected noise. Turn the DUT off to make sure that the noise goes away. Turn the DUT back on to make sure that the noise comes back.

The first thing I noticed; there is more noise during the daylight hours than at night. This is interesting. I thought it might be coming from my solar system, which uses individual inverters for each panel (so-called microinverters). These are wired to 240 VAC but have an internet gateway device that is in the house and communicates with the inverters using a power line data scheme. It turns out this was a minor contributor below the AM broadcast band.

By process of elimination, here are things that were not contributing to RF noise on Medium Frequency (AM band):

  • Cable Modem (Motorola MB7420 DOCSIS 3.0)
  • Router/WiFi gateway* (Netgear R6700v2)
  • GB Ethernet Switch (Netgear TLSG116E)
  • Dell Desktop PC’s (three models)
  • Dell Laptop PC (two models)
  • Android phones (two models)*
  • Phillips 4K LED large-screen TV (5PFL5604/F7)
  • LG LED computer monitor (24MK430H-B)
  • Refrigerator (Frigidaire FFTR1835VSD)
  • Stove (GE BP63D W1WH)
  • LG washing machine (WM3400CW)
  • LG clothes dryer (DLEX4501)
  • Bosch dishwasher (SGV68U53UC)
  • Dehumidifier (GE APEL70LTL1)
  • LED light bulbs (Sylvania 9W Ultra LED)
  • Generic incandescent light bulb
  • Furnace (fancy controller)
  • Furnace burner motor**

*These are intentional RF emitters

**The furnace burner motor made a small broadband RF signal on startup, likely the igniter which uses an electric arc. Once the unit was running, there was no further RF emissions noted.

Medium Frequency baseline noise level

The yellow line is the peak hold, the magenta line is the 100 sweep average and the cyan line is the minimum peak hold. I live out in the sticks; there are no streetlights, no stoplights for miles, the nearest cellphone site is four miles away, and houses are spaced far apart.

First, I measured the noise with everything turned off. I then turned things on one by one, noting any changes in the spectrum. For the list noted above, this is the way it looked.

These are a few things contributing to RF noise levels on the MF band.

We have cheap Chinese grow lights to start seedlings for our vegetable garden. We were using these during the daytime hours to augment the low sunlight in early spring. I initially thought this was coming from the solar system. The interference was making a massive noise hump between 750 and 957 KHz. The brand of growlight is BestVA B-1000 LED which was purchased from Amazon.

RF noise from Grow Light

Next, somewhat surprisingly, the LG computer monitor on my desk was creating a pretty decent rise from 1120 KHz to 1700 KHz. I have three LG computer monitors, this is the newest only this one creates any RF noise.

LG 240P500 LED monitor

Then, pretty much every florescent lamp (compact or full-length tube) created a broadband noise increase across the entire MF band and well into HF.

Florescent lighting

The vacuum cleaner makes a little bit of broadband RF noise when near the receiver. However, you cannot hear the radio when the vacuum is running, so that does not seem to matter.

None of these are surprising. However, I was more surprised that many other electronic devices are not contributing to RF noise in my house.

A little bit about data over power line or power line communications. Searching for power line data can be a bit tricky. First, there is this large voltage 60 Hz (plus harmonics) waveform to deal with. Secondly, there are many different protocols and many different frequencies. I narrowed down my solar system by listening to my Kenwood R-2000 below 300 KHz. Some noise went away when I completely disconnected the inverters. I don’t know the exact frequency, the protocol, the modulation type, etc. But there is something.

Data Over Power line is popular with home automation systems, it can be used to extend Ethernet LAN, and some power companies are using it to control substation equipment, smart power meters, and/or to function as an ISP for their customers. I have heard some HF users complain about BBPL, but I have not experienced it for myself.

Special Equipment

This year, winter in the Northeast has been relatively tame (so far). As I type this today, the temperature is 60 degrees F. The average high temperature this time of the year is around 40 F. This is an anomaly due to the strong El Nino currently going on in the Pacific Ocean. Next year will likely be closer to normal.

To that end, one of the problems in winter time is access to mountaintop transmitter sites. Several of the sites we maintain can only be accessed with special equipment such as a snowcat, track machine, or snowmobile. We have two or three sites that are cut off from regular vehicular access for 2-4 months per year. One site in particular has water flowing down the access road from a reservoir creating a 200-foot sheet of ice that is not even walkable.

For many years, I have been on the lookout for some special equipment that will allow us to get there safely and back.

Meet the special equipment:

Polaris Ranger 900 with studded tracks
The wheels were replaced with tracks and we added this stud kit for ice
Polaris Ranger 900

Like other such items, there is a cost associated with owning this. In the past, we have paid a two-way radio company that has a larger snow machine for rides to the top of various mountains. That can get pricey if several trips are needed. We will have to figure out a reasonable fuel surcharge for the operation of this track machine.

TV sweeps

We have been really busy this fall working on multiple projects plus the day-to-day tasks. One thing that is always fun; sweeping antennas with a VNA.

In this case, WVIT Hartford, CT needed to repair a leaking transmission line section just below the antenna. To ensure that there would be no problems with return to the air at full power, we did a before sweep and after sweep.

WVIT is the ATSC 3.0 lighthouse station for the Hartford Market. FCCinfo.com has the station listed as ATSC 3.0.

WVIT Tower, Hartford CT

The WVIT tower is 1,100 feet tall and is located on Rattlesnake Mountain near Farmington, CT. Most of the other Hartford TV stations are on the same hill.

Tower crew, hitching a ride to the top
Selfie; return loss looks good

It is always interesting to see new places and meet new people. This site has an auxiliary TV studio, which they were using during COVID.

Watching the weather

The weather affects many things. When the weather improves, outdoor projects like tower work can be completed. When the weather is terrible, we may need to do extra work restoring broadcast signals. Today, I am looking at Hurricane Lee, in the North Atlantic basin. Historically speaking, September is the month when we get Hurricanes in the Northeast.

As of this writing, it is too early to be concerned about Lee. Hurricanes can be very unpredictable and there is a good chance the forecast will change many times over the next week or so. That being said, this time of year is a good time to call the fuel companies and top off the generator tanks since winter is coming in a few months anyway. As the situation develops, I may need to dust off the pre-storm checklist.

The basic pre-storm checklist looks something like this:

  • 96 hours or more before the storm: Schedule fuel deliveries for generators, and top off oil and water as needed. Test generators under load if possible. Check UPS batteries. Make an off-site data backup if it does not already exist.
  • 72 hours before the storm: Coordinate with programming to have backup programs available in the event that the satellite dish is damaged, the internet goes down, etc. Inventory and restock PPE, emergency food, water, blankets, first aid supplies, batteries, etc.
  • 48 hours before the storm: Procure supplies needed to secure buildings and sites (plywood, tarps, sandbags, rope, nails, screws, etc). Work out backups for internet STL systems if possible. Work on access plans to remote sites. Make sure that you have the proper tools available.
  • 24 hours before the storm: Secure your personal dwelling, and make sure you have a plan for pets and loved ones. Secure proper shelter for everyone. Fill vehicle gas tanks, and fill portable gas tanks. Update off-site data backup and secure in a safe location.
  • 12 hours before the storm: Secure buildings, park vehicles in areas where they will not be damaged by flooding or blowing debris, and make any last-minute supply runs for emergency food and water. Have a set or two of dry clothes and shoes in your vehicle (almost nothing is worse than spending 12-24 hours in wet and cold clothes). Coordinate response with other station personnel, prioritize the order of restoration, and coordinate with local authorities on their needs.

A few years ago, I purchased one of these LiPo battery chain saws:

DeWalt battery chain saw

These are great units because you do not have to carry cans of 2-cycle gas around. This model will cut trees 12-14 inches in diameter and I get about 25-35 minutes of cutting time per battery depending on the motor load. I have used it several times to cut small trees from access roads to tower sites.

Above all else, during and after the storm, be safe. Do not take any risks involving downed wires, damaged towers, satellite dishes, etc.