Interference on TV Aerial/ Antenna Systems All You Need To Know
If you’re suffering with a poor TV signal, there can be multiple reasons for this. Some most common reasons for a bad TV signal are too much signal, not enough signal, damaged/ faulty equipment and many other reasons including interference. You may be wondering what can interfere with my TV signals? What type of interference do I have? And what can I do to resolve this? In this blog, I attempt to give a relatively detailed explanation on the different types of TV interference and what the potential sources of this might be. Please note that this is sort of a sister blog to our blog on ‘types of TV filters’ so I recommend that you read that when you’re done here. Let’s begin.
Interference on Digital TV Picture
There are lots of different types of interference which I detail below, some of which can be easy to identify like interference from telecoms masts, others can be more difficult like some sort of impulse noise. I have had even a several enquiries reporting of the ferries that go to Isle of Wight interfering with signals in places like Portsmouth. In the old analogue days, TV interference could usually be seen as lines on the TV screen which may come and go, you must remember when a mobile phone would ring and for a brief period of time while it connects you would get lines on you picture accompanied with a short pulsing sound, this isn’t the same with digital TV where interference can be catastrophic as it can cause your TV to break-up, become blocky and pixelate or it can cause complete loss of signal, either way your stuck with a TV picture that you won’t be able to watch. Primarily most interference on TV signals is with regards to when a TV signal is received via a conventional TV aerial/ antenna for terrestrial TV services. It’s not impossible that you can get interference on your satellite TV signal or cable TV signal, it just isn’t as common.
How Does Interference Cause Problems With TV Signals?
It helps to think what a TV signal is, it is essential and exchange of information over the air via radio-waves, an interfering signal or source of interference will disrupt this process. Most different services use different frequencies meaning they do not overlap one and another but this doesn't mean they can't cause problems. The two main problems that I have identified in my experience are when an interfering signal is very strong and overloads the TV tuners/ distribution equipment and the other is when the interfering signal is within the frequency range that you wish to receive. This doesn't have to be strong, just enough to ruin the Carrier to Noise readings, an example of this would be Co-channel interference. Something that you should be aware of is that, with radio-waves you get harmonics and different frequencies can interact with each other cause peculiar problems on certain frequencies
Radio Frequency Interference/ Electro-magnetic Interference
Radio Frequency Interference (RFI) is a type of electro-magnetic interference, although the terms are generally interchangeable with regards with dealing with interference on a TV picture there is a subtle difference. Electro-magnetic interference (EMI) concerns any frequency whereas RFI only concerns itself with the frequency range of radio waves. With today’s wireless world there are so many potential sources of interference that you should be aware of as these can cause problems with your TV viewing, especially on services like Freeview, BT Vision, Soarview.
Interfering Sources Around The Home
With today’s wireless technologies there are lots of potential sources of interference that can ruin a TV signal, around the home for example we have:
Wireless Internet Routers
Mobile phones & tablets
PC’s & laptops
Wireless alarms, CCTV cameras, wireless thermostats and much more
If you’re having trouble with interference, it’s a good idea to try and keep some distance between your TV equipment and the interfering source. If you’re having problems from a nearby source of interference you should be able to identify the culprit without the need for a very expensive piece of kit called a spectrum analyser by just cutting of the power to each item and seeing if the TV reception improves. I have included a couple of stories below of call-outs I have attended when nearby electrical equipment has ruined TV signals.
Impulse noise is a type of fast, almost instantaneous type of electro-magnetic interference. Examples of impulse noise inc., interference from car and vehicle ignitions, interference from electrical equipment, sparks on hobs/cookers, lights and so on. Impulse noise usually only lasts a second or two so any pixilation on the digital TV screen will only be for a brief period but if the source creating the impulse noise is used frequently it can cause constant or regular disruptions to your TV picture.
Co-channel Interference is when you have an interfering signal on the same frequency/ UHF group of the signals that you wish to receive, an example of this would be two nearby TV transmitters broadcasting on the same frequency or nearby frequency with analogue transmission. The interfering signal becomes a problem when it comes to a certain strength in relation to your desired frequency, the two come together and knock each other out.
Fixing co-channel interference can be tricky and sometimes there are very few things that can be done about it. You can’t install a TV antenna filter and try and filter out the interference because it is on the same frequency that you wish to preserve, meaning if you filter it out you will filter out some (or all) of your TV channels at the same time. To have any success in resolving co-channel interference you will need to identify the source of the interference. You may have success by using a more directional TV antenna to increase the forward gain of your TV aerial reduce unwanted signals, but the success of this would depend which direction that the interfering signal is coming from. You could try and cleverly install the antenna in a position where a nearby wall, or the chimney stack itself is used to reduce the strength of the interference. If all else fails you could try aligning your TV aerial to a different TV transmitter that is not effected by the interference, this may mean using a transmitter that offers a weaker signal in your location (not always a problem, I recommend reading TV Signal vs Quality for more info)
Interference From Telecoms/ Mobile Phone Masts
As telecoms masts are broadcasting radio-waves, often very similar to or close to TV signals use by TV aerials and satellite TV, these can cause problems with your TV reception. This is a form of RFI. Detailed below are some of the most common types of interference from mobile phone masts.
4G Interference (800Mhz)
4G mobile internet which is a telecoms standard which allows for talk, text, internet and video streaming. It currently broadcasts on various frequencies including 800Mhz, 1400Mhz, 1800Mhz, 2100Mhz, 2300Mhz & 2600Mhz, but it’s primarily the 800Mhz band that causes the most problems for terrestrial TV/ Freeview reception. This is because this frequency band used to belong to terrestrial TV services meaning a lot of TV transmitters used to broadcast on this frequency and many aerials (if they haven’t been installed in the last few years) are designed to receive this, which if above a certain strength can overload your TV tuners/ TV equipment. Most new aerials and distribution equipment is designed to reject/ filter out these frequencies. More on 4G interference.
5G Interference (700Mhz)
At the time of writing this, the aerial and satellite TV sector are currently undergoing the 700Mhz clearance which will see a further reduction of bandwidth reserved for terrestrial TV services like Freeview, Soarview so that the 700Mhz frequency range can be sold off for 5G services. It’s difficult to summarise what 5G is but it is essentially it is further improvements on 4G, which is the basis for the Internet of Things (IoT). With regards to interference of TV signals it is the 5G coverage layer which offers the most problems. Again, as TV aerials and distribution equipment is designed to pick up and distribute this frequency it can cause problems when it becomes too strong. Going forward more and more TV antennas and amplifiers will have inbuilt 5G rejection, but filters can also be installed to resolve your issues. More on 5G interference.
Tetra Interference (395Mhz)
Tetra, which stands for Terrestrial Trunked Radio and is telecommunication system used by governmental agencies and public emergency services. The problem with Tetra signals and TV interference is it’s relatively close to the TV broadcasting frequencies used for terrestrial TV services like Freeview. In the UK it uses the approximate frequency range of 380-395Mhz in the UK which is not far below the lower end of the UHF. Tetra interference is not as common as it used to be, particularly since most TV aerial/ sat manufacturers now include Tetra filters in built into things like amplifiers but it can be a problem when it get’s above a certain strength, usually when you’re near a transmitter or your TV aerial antenna also points in the direction of the Tetra transmitter.
10 Tips For Solving TV Interference Problems
TV inference can usually always be solved one way or another .Identifying the exact type might be difficult without the appropriate equipment but if you follow the guidelines and suggestions below you should be successful.
1- Use only double screened coaxial cabling, there are lots of makes and types, some better than others. I recommend reading my blog on coax cables but a double screened cable not only has the cable braid but also a constant metallic screen in between the braid and the dielectric. This prevents interfering signals penetrating into the cable itself.
2- Use only screened connections. A screened connection is one where the cable termination is itself enclosed within a metal housing, this can also be achieved with equipment with an F connection as the F plugs themselves will act like a screen. All of your aerials, splitters, amplifiers, wall-plates, distribution equipment should have a screened connection.
3- Install an aerial with an integrated balun or log periodic design. A balun, which stands for balance to unbalanced transformer matches the balanced aerial to the unbalanced coaxial cable, thus it balances the system. Interference can be picked up on the cable screen itself and transferred back into the system, a balun will reduce this as at the aerial as interference can be “fizzled” out. I use that term as that was the exact term that is used in my book by Bob Calaz. A log periodic is also suitable and doesn’t need a separate balun because it works different to conventional yagi-type aerials.
4- Install an aerial with in built 4G (800Mhz)/ 5GRejection (700Mhz). Most new aerials that are purchased nowadays will be designed to either reject or to not be designed to receive signals from nearby 4G and 5G signals. If you’re installing a new aerial it might be a good idea to check this, look for Group T or Group K antennas or if using a Group A transmitter a Group A aerial. I recommend first checking the broadcasting frequencies of the TV transmitter that you’re using as you don’t want to install a TV aerial that is not compatible.
5- Install a filter to remove the interference. There are lots of different types for different types of TV interference. It’s important that the filter is installed before any amplification or distribution equipment so that the interference is attenuated before it enters this equipment and not over-load it and so that all the TV positions fed from the amplifiers/distribution equipment get the benefit of the same filter.
6- Install your aerial high up outside where possible, chimneys/ gable end of building are usually the best positions. There are a couple of reasons for this, one because this is where the signal is usually strongest which offers more protection from many types of interference and two, this is usually keeps a nice distance between interfering sources around the home and nearby at ground level and the TV antenna.
7- Install amplifiers with in built filtering. At the time of writing this most amplifiers will have in built 4G filtering (UHF Channel 60 and above) and Tetra filtering but going forward these will likely soon be regularly available in in built 5G filtering (UHF Channel 50+).
8- Install aerial strategically to reduce interference strength. If you know the source of the interference, the aerial itself often can be installed in such a way to reduce the strength of this. For instance you may find that adjusting the TV aerial/ antenna alignment can reduce the interfering signal strength, or by installing your aerial so nearby walls block out unwanted signals while preserving the ones you wish to keep. A cleverly installed aerial, using the chimney itself can often do this.
9- Align TV aerial to a different transmitter. You may find in your location that one transmitter will always offer unreliable reception because of interference, often you can align you TV aerial to a different transmitter which doesn’t have this problem, this transmitter might even be received at a weaker level but offer more reliable reception. Just make sure you tune your TV for the new transmitter which will use different frequencies.
10- Move TV/ interfering sources further apart. If you have identified the source of your TV interfering as something within your home it may be a good idea to move these so that there is a bit of distance between your TV and interference. For instance it’s not idea to install your wireless broadband router beside your TV or AV equipment and you may want to move your router to a new location.
Real Life TV Interference Stories By An Installer
Bit unusual for my blogs but I have included a few stories of mine through the years, hopefully they will provide some value and/ or entertainment to you.
Nearby 5G Transmitter
At the time of writing this, I literally visited this property in that had trouble with interference from a 5G transmitter that had been installed just across the road in Brighton. The reason I include this because how wrong the company that had attended and attempted to fix before I came. After the 5G transmitter was installed my customer quickly had trouble with their TV reception, this should be an easy fix with a filter installed in the correct place. Rather than do this the company had installed a new aerial in the loft aligned to the Whitehawk transmitter, the old on the roof actually worked better picking up signals from the Rowridge transmitter on the Isle of Wight. Installed a new 8 way distribution amplifier, again the existing one worked fine and installed a masthead amplifier and power supply unit, it’s not often you need more than one amplifier within a domestic environment but in this situation the amplifier they had installed was a variable gain one, 1dB-20dB with the gain turned all the way down, so as not to overload the distribution amplifier I assume. The obvious question you will be asking yourself was why add the amp with the gain all the way down if it wasn’t splitting the signal and thus over coming the signal losses? The answer was no reason what so ever, all if would have been doing is adding to the noise figure of the TV signal. After doing all this for £400, very over-priced the customer was still having trouble with reception. I turned up, removed all the equipment the previous installer had fitted and re-connected the system that was their previously which fortunately had been left in situ. I installed a 4G filter (5G mast but it had 4G equipment on it also) before the input of the distribution amplifier and tuned and tested the TV’s which now worked fine. I spent half the time at the job removing all of the unnecessary equipment that had been installed so that hopefully she can get a full refund.
New Aerial Installation, Interference From Broadband Router
My second story is what we refer to as a “re-call”, this is when we have recently carried out an installation but there are problems with it. I consider myself a good installer so this doesn’t often happen but I also like to look after my customers so rather than argue I nearly always return to investigate even when it isn’t my fault. In this particular incident I installed a new TV aerial in Pevensey Bay just outside of Eastbourne, East Sussex. The location where is it was there is very flat land immediately north/ west of it and you can see the Heathfield transmitter on a clear day, this means that it was a good signal even though the aerial was not installed high on a bungalow. The next day I got a call saying that the reception was very poor which I thought was strange. Upon arrival I saw that the customers broadband router had been installed immediately beside the TV. When I moved it a couple of feet away, the reception improved and when I went closer it immediately got worse. Fortunately, the customer could see what the problem was. Most TV’s tuners are usually screened to some degree to protect against situations like this but in this instance the TV really didn’t like being installed beside another transmitting device.
TV Interference Questions – In Blog Comments Section Below Only Please
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Until next time,
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