Freeview signals: too much of a good thing is bad for you
Most people will experience nothing but simplicity and joy with the digital switchover - the process that turns off the old five high power analogue signals, and the existing six low power digital services and replaces them with six new high power Freeview multiplexes.
For those with problems, there are generally three issues.
Eliminating other possible problems firstThe first is that very, very old equipment will not function with the digital signals split into 6,817 sub-signals, as it was only designed to work with 1,705 sub-signals. This is known as the "8k mode issue" - see TVs and boxes that do not support the 8k
It is also common that people do not clear out the old channel list (by selecting "first time installation" retune, "Factory Reset" or "Shipping Condition") before doing an "autoscan" for the available broadcast frequencies, and this results in everything from missing channels to no subtitles, programme guide, wrong channel numbers and no text services. If you can't find how to do it see either Freeview Retune - list of manuals or do it this way: My Freeview box has no EPG, is blank, has no sound or the channel line up is wrong .
A third problem is caused by having signals from more than one transmitter - see Digital Region Overlap.
The final very common issue is "too much signal".
Transmitters have much more digital power after switchoverAt most transmitters, the digital signals after switchover are considerably more powerful than before. This was because when the analogue and digital services ran together, the digital services were kept low to prevent appearing as snowy interference on television sets using analogue reception.
Here is an example, from Sutton Coldfield, of how the signals change at switchover:
4,000kW of analogue signals are turned off, and the digital services increase in total power from 48kW to 1,200kW - that is an increase of 25 times in numerical terms, also know as +14dB. (The reduction of -7dB from the analogue strength is intended - the digital services require less power to cover the same number of homes).
This large increase in power should cause no effect for most people. A stronger signal does not increase the picture quality (you need Freeview HD for that), sound levels - the only effect should be that more homes that are further away from the transmitter mast can receive a stable digital signal.
High gain aerials and signal boostersHowever, many people have been tempted into buying one both high gain aerials and signal boosters.
High-gain aerials were very suitable for places where the Freeview signal before switchover was very weak indeed, but if you have one of these and you are located closer to the transmitter, you will probably now have a signal overload.
Generally speaking, signal booster devices are never really much use for Freeview reception, and much of the time they actually amplify the interference more than they do the signal, causing reception to get worse, not better.
How to tell if you have too much signalThere are almost as many ways for a Freeview box to display the "signal strength" and "signal quality" as there are types of Freeview box. Here are some of them:
Speaking generally, there will be two indicators:
One is signal strength - this shows the power level of the signal entering the Freeview box. Often "0" is the lowest and "10" the highest, but sometimes it can be a percentage, sometimes coloured boxes and so on.
The signal strength should be around 75% - more than this indicates too much signal.
The other measure is the signal quality and this is much more important to high-quality Freeview viewing. Any measures that increase this to the maximum will provide for uninterrupted viewing, lower values will result in "bit errors" that cause the picture to freeze and the sound to mute out.
One problem with over powerful signals is the overload can sometimes show as a low signal because the receiver circuitry will enter a "blown fuse" state to protect itself.
How to deal with too much signalFirst, if you have a booster or amplifier - remove it from your system. Don't just unplug the power, as this will result in no signal getting though the device.
If you can't just disconnect the output cable and connect it to the input cable, you might need a coax female-female coupler to connect two male connectors together.
If you don't have a booster or amplifier, you might have to fit an attenuator onto the cable. They come in two types, either a "single attenuator", around five pounds, or a variable attenuator, for around ten pounds. The variable sort has a knob that can be turned to select the required level of signal dampening.
Tom : Although the ST5 area is approximately 33 miles away from Sutton Coldfield, however the first part of the code is not precise enough for reception assessment purposes, basically because the field strength of the signal in this area is predicted as only being around 36dB, too low for reliable reception.
A full post code or alternatively one from somewhere nearby, e.g: a shop incl post office.
|link to this|
The Belling style coaxial plugs are not the problem but it is the way someone has wired it up that is. It is a simple matter of ensuring that the centre conductor is fitted properly into the centre pin (and tightened correctly if it is of the screw type or soldered if it is of the older style) and ensuring that the outer braiding has been opened up correctly and wrapped around the compression collar so that it makes good contact with the main body but does not leave any fine filaments free to touch the centre core. Over my years in the industry I hate to imagine how many thousands of these I have fitted and re-fitted. The plug is not the problem then, but fingers and bad workmanship are.
|link to this|
steve burton: Check at the end of your channel list (numbers from 800 and up) and you will likely find the BBC North East Channels. If your recorder allows you to edit the channel list you could delete them, otherwise please provide a postcode so we can see which North East transmitters are providing a signal at your location then further advice can be offered.
|link to this|
I have a problem where only some of the freeview channels have too much signal. for example the bbc freeview channels are perfect with 1005 quality, but other channels like sky news itv channels have 100% strength but very low quality.
if I semi remove the arial I can lower the signal strength and have perfect itv. sky news etc coverage but lose the bbc channels.
how can I get perfection for the two groups of channels simultaneously??
|link to this|
gregor pirrie: What is the signal strength on the BBC channels? You could try an attenuator (see link below) which plugs between the aerial and TV to reduce the signal strength, try 3dB and 6dB attenuators (you can plug them together to give 9dB of attenuation if needed).
6dB Coax Plug Inline ATTENUATOR: Amazon.co.uk: Electronics
|link to this|
gregor pirrie: What is you signal strength on each mux? 75% should be perfect on each one, but obviously some will be slightly stronger than others. But its very odd that by killing the signal a bit, the BBC mux goes
Look at your cable - if its damaged then the BBC mux might unusually weak, whilst others are too strong.
|link to this|