Antenna Interference Issues

A major issue some antenna users face is interference being picked up by their antenna, causing problems with the received signals on the TV set.  This can be very frustrating, especially when you are watching your favorite show! 

Digital TV sets are designed to work with a lot of RF signals coming into them from many sources.  The TV receiver includes something called “forward error correction”, which can compensate for lost digital information up to a point.  However, it is limited in how many errors it can correct.  If there is a lot of interference, too much digital data may be lost, and the TV receiver can no longer correct the errors, resulting in pixelization, freezing images, and sometimes complete loss of signals.

The first step in eliminating interference should be to make sure that you are getting the best quality signal you can get to your TV set.  This includes making sure that you have a high-quality TV antenna designed for your location, high quality coaxial cable, F connectors, splitters, and amplifiers, and that all connections are tight.  Loose connectors will almost guarantee signal quality issues, including allowing unwanted RF signals to get into your home OTA network.  However, even after installing the best equipment and ensuring it is installed correctly and all connectors are tight, you can still receive interference.

Where do these interfering signals come from, and is there anything you can do to solve the problem?  Quick answers: 1) Everywhere, and 2) Maybe, maybe not. 

Let’s start by talking about where the interfering signals come from.  Two of the most common sources are:

Both of these types of interference can be easily minimized by using the appropriate filter to eliminate those signals. 

Other sources of radio frequency interference (RFI) from outside the home include different radio services (land mobile radio systems, pager systems near hospitals, ham radio operators, etc.).  In most cases, these services are being operated within FCC rules, but may be strong enough to overload the tuner in the TV set.  These types of RFI can be a challenge to eliminate, but it may be as easy as just aiming your TV antenna away from the source.  Sometimes, removing an amplifier, or adding an attenuator inline, will work since it will reduce the signal level, possibly eliminating the tuner overload issue.  But it may also mean that you will lose some of the more distant TV stations you are trying to watch.

Much more difficult to identify and eliminate are interfering signals from many devices in and around the home that are called “unintentional radiators”.  These can create radio frequency (RF) energy, even though they aren’t radio transmitters.  These RF signals can then interfere with TV sets and other electronic devices.  The FCC does have rules regarding allowable levels of RFI from unintentional radiators, but some manufactures ignore these rules.  Also, some sources of RFI are exempt from the FCC rules, and, in some cases, even if the device is in compliance with the FCC rules, the unintentionally radiated signals can still cause RFI problems, especially when trying to view a weak TV station.  Three major sources of RFI include:

  • LED and compact fluorescent light bulbs – there are numerous documented instances of interference from some low-cost LED and compact fluorescent lights that don’t comply with FCC rules.
  • Agricultural “grow” lights and industrial arc lighting – these are typically exempt from FCC RFI rules, and can be a strong source of interference.
  • Solar Panels – a significant percentage of solar panels, which are also exempt from FCC rules, create a large amount of RFI problems from the inverters that convert the DC from the solar panels to AC used in the home. It is possible to make inverters that have minimal RFI, but that adds cost.  Since it isn’t required by the FCC, some manufacturers will not add the filtering into their inverter designs to save cost.  If solar panels are found to be the issue, contacting the manufacturer is recommended.  They may have a solution, although it might add cost.

There are numerous other potential RFI sources, including microwave ovens, neon lights, touch controlled lamps, electric blankets, fish tank heaters, air conditioners – essentially, anything that requires power to work.  Troubleshooting these is actually fairly easy if the source is within your home.  Just go around and unplug devices (don’t just turn them off since many are designed to be “instant on”, so are always drawing some amount of power) until the problem goes away.  If the problem doesn’t go away, you may need to knock on your neighbor’s door, and see if you can convince them to unplug devices in their home.  Most of the sources listed above are unlikely to be a problem if they are in your neighbor’s home, but some things, like solar panels and LED lights may be strong enough to be a concern.

Some OTA users have found that this problem may only occur at night, and the TV works fine during the day.  Another earlier blog discusses some of the issues related to RF signal propagation.  As noted in that article, RF signal propagation can and will vary between daylight and darkness due to changes in the ionosphere when it is no longer in direct sunlight.  Also, the electromagnetic energy from the sun varies over an 11-year cycle.  As the electromagnetic energy from the sun increases, interference from distance sources can increase.  We are just starting a new solar cycle, and the energy output from the sun is expected to be getting stronger over the next several years, which may lead to more interference problems as the solar cycle progresses. 

Another reason the interference issues can be worse in the evening is that LED and fluorescent lights are being turned on, more people are home, and more electrical devices are being used in the home.  This results in a higher level of interfering signals that can be picked up by the antenna, causing more interference on the TV.

Finding and fixing sources of RFI can be difficult, can take a lot of time, and specialized test equipment may be needed.  There are a host of articles on finding and fixing RFI that can be found on the Internet, but your best bet may be to find a local ham radio operator that is willing to help.  If you are having RFI problems, there is an excellent chance that your ham neighbor is having the same problems and may already be working on finding the source.