Single frequency interference
Brian Butterworth published on UK Free TV There are several different type of interference that cause problems. This page deals with the situation where:
- Freeview reception is perfect or near-perfect most of the time
- Several channels are missing, but they are all on the same 'multiplex'
Local analogue interference
Local analogue interference is caused by household video devices that you can attach to a television such as: If you have any of these devices, you will need to work out which of these is blocking the reception of a Freeview multiplex by turning off the suspect device and then rescanning for channels on the Freeview box.If powering off the device restores the Freeview channels from the blocked multiplex, you will need to either stop using the problem device's RF output by disconnecting the RF output cable permanently, or by changing the RF channel number that that device uses. See, for example, How do I change the RF output channel on a Sky Digibox?
You can find a list of the frequencies that are not in use at your location by putting your postcode into the My Freeview reception and looking under the "Free RF channels" section.
Non-wideband aerial in some areas
In some places you will need a wideband aerial to receive all the Freeview multiplexes. For example in Central Birmingham, the Sutton Coldfield has multiplex D on an 'out of group', so you cannot view Film4 or ITV2+1 without an aerial upgrade.To find out if you need an aerial upgrade, see My Freeview reception.
Help with Freeview, aerials?
Tuesday, 16 March 2021
C
Chris.SE11:25 PM
djlewis:
Retuning when you have no signal is never a good idea, it usually just clears the correct tuning, and you have to repeat a retune when signals are normal.
Whilst it's usually possible to track any reports of recent interruptions to any BBC channels, that's not so for the commercial multiplexes.
There is currently no Planned Engineering at Wenvoe and there are no current Live issues being reported by Freeview.
So try a manual retune on UHF C45 which carries the ArqA/COM multiplex at Wenvoe and hopefully the channels will be restored.
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Thursday, 3 June 2021
J
Jim Sinton7:09 AM
I have 2 TV's including a new one where the audio is delayed by about 1 s from the video. This is without using any sounbar etc. Have factory reset both and still have the issue. This only affects the HD channels on free view. Struggling to think what it could be other than a broadcast problem. I am on the Windermere transmitter.
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C
Chris.SE3:26 PM
Jim Sinton:
Hi. It's very unlikely to be a transmission fault if it's happening on one set and not another. You could also check with neighbours that they aren't having the problem.
There's no Planned Engineering currently listed or reports faults by the BBC or Freeview.
I'd very carefully go through your sound settings when watching an HD channel. Some sets do have settings that allow you to adjust the sound sync and a reset may not reset them back to 0.
If the problem is still ongoing, post the make and model number of the set, someone may know about an issue.
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Friday, 11 June 2021
A
andy2:33 PM
Afternoon I've bought a Technomate TM-RF HD IR and wondering if any one could help me on what would be the best channel to have it set to as I'm getting some interference on the channel I have it set at at the moment, and I don't want to lose any of the channels, I think I'm in the winterhill transmitter as I'm over in Stockport
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Saturday, 12 June 2021
C
Chris.SE8:58 AM
andy:
I would try anything above UHF C60, so that should be far enough away from C55 (COM7).
Anything lower might give interference if the device produces any harmonics or it or any equipment has strange C+5 or C+9 effects.
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C
Chris.SE9:11 AM
andy:
Oh, to add to the above, make sure the HDMI leads are not close to any of the RF leads. The RF leads should ideally be quality double screened types, as HDMI has been known to cause interference, especially to C55.
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Thursday, 26 August 2021
R
Ron6:26 PM
Watford
Starting about one month ago, we can't get decent/any reception on COM5 (ARQA on your list).
We are on the Hemel Hempstead transmitter and get COM6 on C29; COM5 on C31; COM4 on C37; PSB1 on C40; PSB2 on C43; & PSB3 on C46.
The signal quality on all muxes except for COM5 is always 95%+ (Usually 100%).
The signal quality on COM5 never goes above 90% and most of the time is less than 30%. Sometimes it goes down to 0% and the picture is completely pixelated and sometimes says, "No Service".
The error rate is regularly above several 100s and sometime in the 1000s.
When this happens, I look at all the other muxes and the quality is 100%.
Surely, if there was an aerial problem, then all muxes would be affected.
We have 5 Freeview TVs in use on a wideband, signal powered aerial and they all have the same problem on COM5.
What is likey to be the problem?
Thanks in advance.
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Ron's: mapR's Freeview map terrainR's terrain plot wavesR's frequency data R's Freeview Detailed Coverage
Friday, 27 August 2021
C
Chris.SE12:45 AM
Ron:
If it's become persistent, then I would start looking for two possibilities - aerial installation or interference.
Firstly check the connections at the aerial and any masthead amp, the coax cable condition and the termination at the amp/splitter or PSU if it's a masthead amp and connections to the splitter.
Faults/corroded connections can affect a single multiplex (but eventually further deterioration could start to affect more/all of them) this is because standing waves can be set up in the cable, this is frequency dependent and depends on the length of cable from the point of fault. It's not that common, but it does happen.
The installation is always worth a check if it's a few years old.
Interference from a variety of possible electrical/radio(RF) sources can again affect specific frequencies only, others can be more broadband. Does the problem occur at the same sort of times every day? Or is it totally random?
If it occurs at the same sort of time every day, have a look at anything that comes on with a time clock or even a light sensor, even lights you switch on manually. Faulty street lights, fluorescent lights, compact fluorescents, older style LEDs can all generate interference. (Filamentary LEDs - clear or frosted, virtually don't generate any interference and are tons better than those with the big plastic cap on the back).
Unfortunately this type of interference might come from a near neighbour. BTW have you asked if your nearest neighbour has the same problem with COM5, that might help narrow things down.
If it's more random, things like boilers for hot water, arcing thermostats, fridges and freezers starting are possible suspects but these tend to be broader spectrum interference so just affecting COM5 is much less likely.
Other things to consider. Have you changed anything in your installation that might coincide with when this started? Are you using any equipment you hadn't used before (or for some time) eg. something with an RF output that may be set to/near C31 - eg. a recorder, old skybox, games console etc.
Does the problem only occur when certain devices or their PSUs (eg. phone chargers) are turned on?
One final possibility (but odd it's only started recently) is you might be in a location where C31 is vulnerable to frequent interference from another transmitter (it wouldn't necessarily apply to all multiplexes) but we'd need a full postcode to look at the predicted reception in your locale.
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Wednesday, 5 January 2022
S
SteveK4:44 PM
Haywards Heath
Me again. Heathfield transmitter. RH16 3RX.
As we progressed into winter my reception on on C46(674.0MHz) crashed. Virtually zero strength and zero quality and lots of bit error. Variable but useless. This has now improved slightly but very dodgy and unwatchable. However C47(682.0MHz) is now frequently crashing and I am having to switch to C41(634.0 MHz) to watch main terrestial channels.
Is it the weather?
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SteveK's: mapS's Freeview map terrainS's terrain plot wavesS's frequency data S's Freeview Detailed Coverage
Thursday, 6 January 2022
C
Chris.SE4:40 PM
SteveK:
Well it could be weather but NOT tropospheric ducting at present. It's more likely to be a problem with your aerial installation - assuming it's an external aerial and not loft mounted.
I would check that your aerial seems intact and pointing in the correct direction (bearing 93 degrees - almost due E) with the rods (or squashed Xs) horizontal (even if it's in the loft - they can get accidentally disturbed) and that your downlead looks undamaged and isn't flapping in the wind if external.
Also check all you coax plugs, connections, flyleads etc, unplug connectors check for corrosion or other problems and reconnect them. Flyleads can be a common problem, try swapping them.
See what signal strengths (if any) and quality you are getting for the multiplexes shown in your TV's tuning section, this might indicate potential issues with your aerial or downlead.
If you post the figures for each it may give us a clue.
I notice a while back you reported signal strength and quality, if you did attenuate the signal what is it now, any attenuation may not have been needed.
Faults/corroded connections can affect a single multiplex (but eventually further deterioration could start to affect more/all of them) this is because standing waves can be set up in the cable, this is frequency dependent and depends on the length of cable from the point of fault. It's not that common, but it does happen.
The installation is always worth a check if it's a few years old.
Do you have a distribution amp/splitter and where is it located? If you have one, check that it still has power and check the connections to it.
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