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Single frequency interference

What to do when several channels are missing, but they are all on the same 'multiplex'

What to do when several channels are missing, but they are all
published on UK Free TV

There are several different type of interference that cause problems. This page deals with the situation where:

There are two main causes of this type of intermitted interference: The current Freeview mulitplexes are shown in this diagram. If all of your missing channels are on a single row, you have "single frequency interference":



Local analogue interference

Local analogue interference is caused by household video devices that you can attach to a television such as:
  • Sky Digibox;
  • Video cassette recorder (VCR);
  • Personal digital video recorder (PVR);
  • Games console;
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?
How do I get a test card with Freeview1
I would like to know if it is possible to receive UK terrestrial Freeview servic2
I have been told I would receive too much singal from my Freeview tansmitter as 3
Can my Freeview box receive more than one BBC and ITV region?4
Is it true that my 87 year old mother is entitled to a FREE upgrade when the ana5
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In this section
Official aerial installers guide to the TV spectrum future1
Which free digital TV system will give me the most reliable reception?2
High pressure causing channel loss through "Inversion"3
Digital Region Overlap4
Freeview reception has changed?5
Two frequency interference 6

Comments
Tuesday, 12 November 2019
S
SteveK
10:38 AM
Haywards Heath

Chris.SE - thanks for this. All channels on C47 now unwatchable. Hope rectified soon.

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SteveK's 9 posts GB
Saturday, 8 August 2020
I
Ian Lythgoe
11:18 AM

Located at Ross on Wye. Receiving from the Ridge Hill transmitter.
Keep losing signal to several Freeview channel. Seems to be SDN channel 21. signal loss is very short less than 30 seconds and seems more frequent In higher air temperature. Fault has been occurring for several weeks.

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Ian Lythgoe's 1 post GB
Sunday, 9 August 2020
C
Chris.SE
sentiment_very_satisfiedPlatinum

7:01 AM

Ian Lythgoe:

Neither Freeview nor the BBC are currently reporting any faults at Ridge Hill and it's not currently listed for Planned Engineering. You might be in a location where reception especially of the SDN/COM4 multiplex is a bit marginal but without a full postcode we can't see what your predicted reception might be.

Whilst there is some variable intermittent "Troposheric Ducting" around at present that's been quite strong in some parts of the country causing interference from distant transmitters (see
https://www.bbc.co.uk/rec….jpg ),
if your issue has been continuous for several weeks there could be some additional reception problem with your installation.

I would check that your aerial seems intact and pointing in the correct direction and that your downlead looks undamaged (especially if it is old). Also check all your coax plugs, connections, flyleads etc, unplug connectors check for corrosion or other problems and reconnect them. Flyleads are a common problem, try swapping/changing them. See what signal strengths and quality you are getting for all the multiplexes shown in your TV's tuning section, it may indicate some issue.
Problematic connections, water ingress etc. can seem to affect reception of just an individual or several multiplexes.


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Chris.SE's 2,560 posts GB
Friday, 21 August 2020
M
Mrs Samantha Bryan
7:03 PM

We have an LG TV linked to aerial in loft. Before 12th Aug TV would pick up all freeview channels but after retune I can no longer receive certain. Uhf channels. The other TV linked to same aerial is picking up all channels OK. I have tried factory resets, manual retunes, automatic retune and aerial out retune, aerial in retune. I seem to be missing uhf 34 and 35. BBC 1 & 2 are fine. Not sure if this is going to be an aerial issue as the other TV picks channels up fine? Getting rather frustrated and freeview help hasn't been very helpful. Any advice would be appreciated.

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Mrs Samantha Bryan's 1 post GB
Saturday, 22 August 2020
C
Chris.SE
sentiment_very_satisfiedPlatinum

5:08 AM

Mrs Samantha Bryan:

Ah, so if Freeview help hasn't been helpful we need to know why! We also need a full postcode to look at your predicted reception.

To save me repeating a lot of information I've already given, see my post Winter Hill (Bolton, England) Full Freeview transmitter | free and easy and the post to which it refers and all the following posts to give you an idea of the issues involved. If you aren't receiving from Winter Hill, the UHF channel numbers won't apply, but the principles are the same. A bit more information about your setup is also needed, eg. is it your main tv? Is it a longer cable run etc. Do you have cable or satellite etc.?

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Chris.SE's 2,560 posts GB
Sunday, 29 November 2020
F
fred
11:08 PM

For the last 4 days Ive been able to get hardly any channels, some of them come back late evening
Whats going on? Weather is good, so why can't I get any channels
Its bad enough in summer high pressure weather when I lose most channels for days on end, but now in winter to!
How can I solve this?
Im in Faversham Kent ME13 postcode

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fred's 1 post GB
Monday, 30 November 2020
C
Chris.SE
sentiment_very_satisfiedPlatinum

4:38 AM

fred:

Apart from seeing my post in reply to you on the Faversham page Faversham (Kent, England) Freeview Light transmitter | free and easy there has been some "Tropospheric Ducting" around with the recent high pressure affecting some parts of the country at varying times (it can occur in winter). If it's continuing to affect you, it should clear by Wednesday and things should be back to normal.

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Chris.SE's 2,560 posts GB
Tuesday, 9 February 2021
C
Cap’n’bob
5:36 PM

This is more of an FYI though comments/answers gratefully accepted for the questions at the end...

I was having intermittent total interference on PSB1 (BBCA) on 4 out of 5 TVs in the house. It also sometimes impacted a bit of COM5 and LCB. The channels would just wink out with a freeze, no audio and zero signal strength for anything from 2 to 45 minutes at a time. The only changes I'd made recently were 2 Roku's added to 2 tv's that worked fine. The problem only arrived a week or so after installing and using the Roku's. All but one device attached to thenTVs are HDMI with one legacy scart on a little used tv.
I disconnected all attached items, checked fly leads and the in-loft antenna and distribution block with masthead amp... all seemed fine (working, not corroded) so I assumed it was something else causing local intermittent interference.

What I found amazed me but it might not wow the experts here. I was watching something which winked out. I noticed that my Mac Mini media server connected with a mini-dp to DVI cable to a modern Acer LED monitor came to life as the signal died. For a laugh, I switched off the monitor and the signal returned immediately. I was staggered. It was easy to replicate and worked reliably. Monitor on with Mac Mini screen showing and the tv signal died, switch it off and it comes back.

Here's the weird part... if the same monitor was on but with no video signal OR a different computer showing on a different input of the same monitor (thunderbolt to HDMI) there was no interference. If it was on the Mini signal, and I gripped the cable, the signal came back.

Questions: should I just replace this mini-DP cable or could it be something else? Does all this make sense? (Still seems weird to me). I can't move the monitor location and it impacts TVs in multiple rooms and isn't close to any fly leads though it is roughly under the distribution box in the loft.

Thanks for any thoughts and hopefully it might help others with weird (digital??) interference?

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Cap’n’bob's 1 post GB
S
StevensOnln1
sentiment_very_satisfiedPlatinum

6:55 PM

Cap'n'bob: How close is the monitor to the aerial cable? HDMI cables (particularly those with poor screening) are a well known source of electrical interference, particularly in the UHF band, presumably other similar/compatible cable types are also capable of causing the same impact. You may find that moving the offending cable and keeping it away from the aerial cable is enough to resolve the problem, or if that isn't practical it may well be worth replacing it with a higher quality properly screened cable (ignore anything about gold plated connectors, it's the foil and/or braided screening around the cable that's important).

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StevensOnln1's 3,153 posts GB
Tuesday, 16 March 2021
D
djlewis
8:03 AM

no com5 arqa channels showing, started on the 14/3/2021, all connection checked and did many tv retunes
transmitter wenvoe.

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djlewis's 2 posts GB
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