Mobile phone signal interfering with digital TV signal

tobervuirich · 10-08-2009, 23:02

We recently converted to digital signal. Before it went live I had a TV engineer turn our aerial to a different transmitter adding a signal booster. I immediately noticed that when a mobile phone received a text or call the TV's would lose signal either partially or completely. I left it thinking the digital changeover might cure it. It didn't. I phoned the engineer and he blamed our cordless phones. However none are near the aerial or TV's. It is only when we receive mobile phone connections. The aerial is in the loft. I put kitchen foil beneath the aerial with no effect. Can anyone help?

Mick Fisher · 11-08-2009, 01:10

Get the aerial re-sited onto the rooftop.

Or better still go freesat.

tobervuirich · 11-08-2009, 08:33

The aerial has always been in the loft with boosters connected. This has only happened since the aerial was turned to receive transmission from another transmitter when the original position was being interrupted by trees. It also had a new booster replacing the one already on during this repositioning.

**Kymmy** · 11-08-2009, 10:23

The booster (as you call it) sounds like it's a cheap one with absolutely no filtering. Where is it sited? If near the TV then most likely it's 100% to blame. If it's in the loft then the phone signal could be being picked up by the co-ax downlead and feeding upto the booster thus causing feedback on the amplification circuit..

The mobile (either transmitting on 800/900 or 1800 Mhz) should not cause direct interference to the TV, neither should a cordless DECT phone at 2.4Ghz, unless the cordless is an old analogue device or one sold for use in another country..

tobervuirich · 11-08-2009, 11:20

The booster is in the loft very close to the aerial. We already had a booster on it and don't know why this one was installed. It is powered. Should the booster be changed or is there any other way to deflect the mobile signal such as aluminium foil. Although I don't think this would work.

heero_yuy · 14-08-2009, 12:15

Try connecting the outer braid of the co-ax to a close local ground where it enters the booster. The normal yagi aerial is unbalanced when connecting to co-ax. Normally this isn't a problem but it does allow stray signals to sneak in.

Although the phone doesn't use the same frequency as the TV it can cause "desensitising" of the TV front end and/or booster by swamping it.

Alternatively try making up a co-ax balun This has the additional advantage of adding some gain to the aerial.

**Kymmy** · 14-08-2009, 13:36

The balun's not likely to stop stray RF from reaching the booster or TV, probably better using a choke balun (either a line of probably type 43 ferrites or a larger ferrite with the coax wound a good 6-10 turns in a double sided pattern)

The coax ground though would probably do good especially again if it's a cheap booster which is double insulated instead of properly earthed