How do I choose the correct TV Aerial?
This is a question I get asked often, what is the best antenna for Digital TV aerial installation in Manchester? Like many things there is no one straight answer as it depends on a lot of factors. Let’s discuss some of those factors that would help determine what type of TV Aerial is best for you.
First things first.
When getting a call from someone needing an aerial install, the first thing I ask for is their postcode. Why? Well apart from helping me get to them to provide them a free survey which is all part and parcel of the service we offer our clients. So, getting the postcode helps me very quickly get a rough idea of what type of TV Aerial the clients might need, how?
UK FREE TV- https://ukfree.tv/prediction this is a website/resource for TV Engineers, or anyone for that matter who might like an idea about:
- Their nearest TV transmitter
- The MUX’s or multiplexes broadcast from that transmitter (channel line ups)
- Expected strength of the Digital TV signal in your area- this is what the Engineer will be looking at! So even before arriving to carry out a more detailed survey, we already know what the Digital TV reception is like in that area.
At the installation
Ok, we have arrived at the customer’s home prepared. We already know from the UK FREE TV website what the expected Digital TV reception strength is in that area. Plus, we also carry numerous types of Digital TV Aerials, masts, amplifiers etc on our van we are always prepared for every eventuality.
So, we will determine how strong the Digital TV signal in that area. Next is a couple of other things before we recommend a particular TV Aerial, and they are:
- Is this an outdoor TV Aerial installation, roof mounted for example, or is this an indoor TV Aerial installation, for example in the loft?
- How many TV points is the customer looking for, just the one, or multipole TV points?
Determining the answers to these questions will help us is in making the correct selection of Television Aerial. Let me explain why.
What about fitting in a Loft
If the client is looking say for a Loft fitted TV Aerial then we would definitely recommend a particular Antenna for that type of Installation. Loft aerials are now becoming at least 40-50% of all our TV Aerial installation. This is because new build properties generally pre- wire TV points in the property and track all the cables back into the loft space. All that is required in these types of installations then is a suitable aerial and a splitter or distribution amplifier. This is to split or distribute the signal to all TV points in the house. A typical 3 bedroom house may have 3 or 4 TV points. Thus requiring a TV Aerial that is powerful enough to split 3 or 4 ways. You do this via a passive splitter (no power or amplification required). In the case that the signal is not quite enough to split passively 3 or 4 ways we will then use a distribution TV signal amplifier. This is to ensure all the points in the house receive a strong enough signal.
Using a Analyser or Signal Meter
We are able to determine the best course of action by the use of a field meter also known as a Spectrum Analyser. This piece of high-tech equipment measures all signal parameters. This helps us as TV Aerial Engineers to know what the best system for each situation will be. For example, a Spectrum Analyser will look at 3 things:
- Signal strength
- Signal Quality
- Interference
It’s important to understand all 3 parameters before deciding on the correct antenna for the job. For example, a strong signal with high quality and little Co Channel interference is the best possible desired outcome to work with. It’s because a good signal can usually be split 3 or 4 ways without any amplification.
Recommended Signal Levels
A signal level say measured in a loft of 67dB at the head end with a low BER (bit error ratio) will produce a signal at the TV point once split 4 ways of about 51dB. That is more than ample for reliable TV reception, the maths is quite simple to do. For example, if the BER (bit error ratio) is low then the only calculation you need to do is deduct approximately 4dB for each TV point added via the passive splitter. This is also known as insertion loss in the trade, and you can estimate the output at the point. So as in the case of our 67dB head end signal with low BER we simply multiply 4×4- 4 TV points losing 4dB (insertion loss). This is how we have a number of 16 dB total loss. We subtract the 16dB loss from 67dB and we have an estimated TV point signal level of 51dB. 51dB is a good signal if the BER is low. 45dB being the acceptable threshold and we are 6dB above J
When there is Interference
Now, if the Engineer reads a good high signal but there is Co Channel interreference, this changes things. The interference has the net effect of causing a greater insertion loss. Effectively you have competing signals and if you split the signal via a splitter as describes above you will end up with losses higher than 10dB per point. Thus leaving you with a signal that is below the acceptable threshold.
Do you then simply add an amplifier to boost the level at the head end? No! This will have the net effect of not only boosting the Digital TV signal but also boosting the Co Channel interreference. What is the solution? Namely to reduce the interreference being received. This can be achieved by choosing a TV Aerial that reduces the reception of impulse noise (interference). We have used the Log Periodic design of TV Aerial to great effect for this purpose. It is because this design of antenna is without a rear reflector favouring two layers of elements running parallel. Rear reflectors on aerials are notorious for attracting all types of signals. So, this would be my go-to solution to get around the Co Channel interference problem. Please see this video review of the Log Periodic:
The next thing is carry out a more detailed survey and inspection. Look for potential causes of interreference & make sure that where the TV Aerial/Antenna is sited is away from possible causes of interference. Devices such as thermostats, Internet boosters and routers or external sources. A Spectrum Analyser will determine where the least interference at the Head end is. This leads to the next question. How do you align a TV Aerial/Antenna?
How do I align my TV Aerial/ Antenna for best reception?
Imagine trying to bake a cake in the dark, pitch black! Ok, you have all the ingredients on the kitchen counter, the flour, eggs, dried fruit, cinnamon spice, baking soda etc and you have all the right kitchen appliances, scales for measuring, food mixer, oven you get the idea. Now how would you mix that cake, bake it all in the dark, and expect to get something edible? Very unlikely! This just illustrates a point I wish to make when discussing the question, how do I align my TV Aerial/Antenna namely installing a aligning a TV Aerial/Antenna WITHOUT a Spectrum Analyser is like baking a cake in the pitch black darkness, you are working blind!
Is a Meter Required
A spectrum Analyser allows you to see things that are invisible to the human eye, like Digital TV signals, Co Channel interference. Yes, you may know roughly where all the others TV Aerial are pointing in your street but believe me that is not the correct way to align a TV aerial. You would not believe the number of times I have been called out to a TV Aerial installation say carried out as a DIY job with a TV Aerial that some guy bought on eBay, but is now installed and not working properly? Too many to count! Often in these situations, I not only have to re-install the TV Aerial, but more often than not replace the TV Aerial/Antenna that the guy had bought on eBay! Having said all that some people do strike lucky and manage to get a half decent signal, however most of the time it’s certainly more miss than hit, like baking a cake blind.
So, how is a TV Aerial/Antenna aligned correctly?
Supposing you have the right measuring equipment – a Spectrum Analyser and you know how to interpret the data- signals levels verses signal quality (BER) then essentially you would do the following: 1) Determine the general direction to the main TV transmitter, here in the Northwest in most cases that would be Winter Hill. 2) Once you have the general direction note possible pathway issues, in other words, look for things in the way that could ‘block’ the signal like trees or buildings, if these are close, they can pose a problem- for example, trees give off small amounts of heat and believe it or not this can really mess with your Digital TV signals, so make sure you are looking for a pathway away from trees. Buildings again can cause issues too as they block signals and can cause ‘bounce’ which is Co Channel interreference from nearby competing signals say from Mobile Phone masts as one example.
What about Obstructions to the signal
So, if there are tall buildings at the same height (roughly) as where you are siting the aerial, then you may need to choose another pathway. First, Choose clear pathway away from trees or tall buildings. Connect your antenna to your Spectrum Analyser or Field Meter pointing the antenna in the general direction (pathway of the signal). Next, select on your meter the weakest multiplex as a base to work from. Get that multiplex (also known as a MUX) at a good level & all the other muxes will all be fine.
Re Siting the Antenna
Now moving the antenna is small left and right horizontal movements keeping a close eye on your two measurements. These being signal level and signal quality (BER). Once you have found the highest signal level, now look at the signal quality. BER, can also be measure as MER. Having done that make even smaller movements side to side and up and down. Do this very slightly untill you see that number improve.
Once you have the best signal strength and signal quality on that multiplex, now go and look at the others. Check all 5 or 6 muxes are equally as good, they generally will be. Make sure you aim for the highest possible level. Then, check that you are well above (especially if you are going to split the signal) the acceptable threshold. this is usually above 45dB minimum and at a maximum of 80dB. Yes, too much signal can cause over modulation. So, pay attention that you don’t take the Digital TV signal above 80dB. Once you achieved the best possible signal, then lock of the clamp on the pole. Ensure it’s as tight as can be so that the TV Aerial remains secure in place and you are all set!
What sort of TV Aerial/Antenna do I need for a smart TV?
Smart TV’s are now the norm. If you are in the Market for a new TV chances are you will be buying a Smart TV. So, what is a Smart TV? Simply put a Smart TV doesn’t just supply you with Terrestrial Broadcast channels. They also allow you to access ‘Apps’ that allow you to watch internet TV. Apps like, Netflix, Amazon Prime Video, Now TV, YouTube and many more internet streaming channels. This is great because you will be able to access more channels than your local TV transmitter broadcasts. The only thing you need to be aware of is that some of these services are internet dependant only. Some of them work in tandem with your normal local Terrestrial Broadcasts.
How does this work?
Well essentially the Broadcaster- say Sky rents space on your local TV transmitter. Thus broadcasting FREE and paid TV channels. However, your Smart TV or set top Box (as in the case of BT Vision) decodes the terrestrial signal using the internet. You will require 2 things for the best Smart TV experience, 1) A good quality Digital TV Aerial Antenna 2) A reliable good quality internet service and you are all set.
I Have heard about High Gain TV Aerials; do I need one?
High Gain TV Aerials Antennas do exactly as the name suggest, they ‘gain’ higher levels of signal. That’s got to be better right? Yes and no. If where you live is a poor signal area- ‘blackspot’ then a High Gain TV Aerial is the one you want. If you live in a High Signal strength area, say in Bolton for example just next to the Winter Hill transmitter, then in that case no you do not want a High Gain TV Aerial/Antenna. This is because as discussed already in this article, too much signal is just as bad as not enough. Hence a High Gain aerial could in some areas not work as effectively as a small contract aerial. This is where the UK FREE TV website will prove helpful. It can help you gauge what type of TV Aerial/Antenna you will need. Again, you should call a qualified Engineer with local experience. He will be able to tell you whether a High Gain Digital aerial is the one for you.
Do Old TV Aerials/Antennas still work?
Again, this is something customers ask me a lot. People move into a new house, they see that there is an aerial on the roof or in the loft, yes it looks ancient but maybe that will work ok?
Like many things this is a ‘suck it and see’ type of thing. But generally, here’s a couple of things you should consider:
- Old Analogue TV Aerials will receive Digital signals though perhaps not all and
- Old Analogue TV Aerials do not have in built 4/5G filters.
Conclusion…
So, what this translates to is this, you may plug in your fancy Smart TV to the old analogue TV aerial and notice that on BBC 1 for example, you have a cracking picture- result yeh? Not so fast! A great picture on BBC 1 doesn’t mean the Analogue TV Aerial is fine. Now go and look at More 4 or Sky News, how do they look? “Those channels are breaking up…” I hear you say. That’s right, the Analogue antenna can see the strongest signals coming straight off the top of the Transmitter. However, it cannot see the signals coming off the bottom? Why not? An Analogue aerial- is designed/tuned for a narrow bandwidth.
It could also be that in ideal weather those lower strength channels work. Then when the rain comes, they pixelate, the solution? A Digital TV Aerial.
Also, if you live near a mobile phone mast remember, that old Analogue TV Aerial on your roof does not have a 4/5G filter built in. So, come 6pm when everyone comes home from work and gets on their phones you could have trouble?
It could also be that you are missing some muxes- these are frequencies that carry multiple channels. I have replaced a customer’s Analogue TV Aerial/Antenna with a Digital one. Then, hey presto we re-tune the TV and another 35 channels are found! So you see why the answer to the question; ‘Do Old TV Aerial still work is both YES and NO.
For help from a professional engineer contact us on the number below.
TV Aerials Manchester, 22 Lever Street, Manchester. M1 1EA Tel: 0161 883 1945
https://goo.gl/maps/zStcQQstZoBTKEkp7
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