Single frequency interference

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

^{Brian Butterworth published on UK Free TV 30th September 2007 at 14:09}

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'

There are two main causes of this type of intermitted interference:

• Local analogue interference
• Non-wideband aerial in some areas

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.