12V TV Interference

oldbloke · Guru

12V TV Interference

valiant81 · Senior Member

Hi all;

Digital break up can be caused by a number of things, everything from the incorrect antenna, or off direction, trees, poor quality cable and fittings, too little signal or even to much signal !!. Having the right antenna for the channels that you wish to receive, even sharp bends in the cable can cause problems. With poor quality cable and running that cable close to other cables , both 12 volt and mains can cause problems with drop out and even turning on a light or motor can cause all sorts of drop outs. sound and or picture freeze. Sometimes ferrite beads may help.

Had a antenna job a few years ago before i retired ( early days of digital tv ) and my customer had three other technicians try and sort out his problem with one of the digital channels that he was unable to be received. Plenty of signal and the missing channel was at the antenna terminals. No one had check on the quality of the cable, reception was good before digital and it was only since we got digital that my customer started to have problems.

In the end a complete rewire from the antenna to the splitter and on to the wall plates and fly leads. Everything was replaced bar the antenna and having a look at the coax cable, i found that is was a very poor quality and the shielding was basically foil and 4 strands of fine wire. Replacing with good quality RG6 cable soon had my customer very happy.

STRETCH ARMSTRONG · Senior Member

I agree with valiant81. Another issue with my tv is the result from the sell off of spare digital tv frequencies(700-840mHz) to mobile phone industry. This has resulted in some 4g and 5g interference if you are within one km of a tower. My vans tv arial is pre 2015 so is subject to the this. You can buy a simple LTE filter that stops any boost to these frequencies. I believe jaycar has them.

valiant81 · Senior Member

STRETCH ARMSTRONG wrote:
I agree with valiant81. Another issue with my tv is the result from the sell off of spare digital tv frequencies(700-840 mHz) to mobile phone industry. This has resulted in some 4g and 5g interference if you are within one km of a tower. My vans tv aerial is pre 2015 so is subject to the this. You can buy a simple LTE filter that stops any boost to these frequencies. I believe jaycar has them.

Hi all; Stretch, You are right with the LTE filter and one thing that i forgot to mention. But these filters have to be inserted right after the antenna and before any form of amplification if a amplifier is installed. If installed after a, say a masthead amplifier the amplifier would amplifier the tv signal and the 4/5g signals and could then be to high a level for the filter to remove effectively .The Lte filter would still work, but because of the higher levels would be less effective in removing the interference. The same goes for FM filters.

-- Edited by valiant81 on Tuesday 12th of May 2020 12:18:06 PM

stoney123 · Senior Member

What happens when you play a movie from a usb stick?

valiant81 · Senior Member

Hi Stoney 123; No problems if you are playing movies off a usb stick. It is the digital tuner that is picking up the interference.

Whenarewethere · Guru

Is the interference happening if the TV is on a completely separate power supply. IE stick the TV on a separate 12v battery not wired through any part of the vehicle.

oldbloke · Guru

USB or DVD player its pervect. Only plays up wnen on dtv . And only if fan heater at home is running. Or if exhaust fan in van shower is running.

Aus-Kiwi · Guru

Try twisting the DC wires ? Or if there is shielded wire ? Make sure its earthed at ONE end . Or the shield becomes a conduit for elect interference .. LED lights can cause issues .

oldbloke · Guru

What would twisting the 12v wires do?

Jaahn · Guru

Aus-Kiwi wrote:
Try twisting the DC wires ? Or if there is shielded wire ? Make sure its earthed at ONE end . Or the shield becomes a conduit for elect interference .. LED lights can cause issues .

What would twisting the 12v wires do?

________________________________________________________________________-

Hi Oldbloke smile

If the interference is being picked up from the 'air' by the power supply wires then twisting the pair may help to reduce the pickup.

If the interference is coming through the power wires from the DC motor running then fit this from Jaycar; https://www.jaycar.com.au/10a-dc-noise-filter-improved/p/AA3074

Installation information; https://www.jaycar.com.au/medias/sys_master/images/images/9399804297246/AA3074-manualMain.pdf

Also fitting an old style ignition capacitor between the power in-put leads might bypass it. Or do all three.

Jaahn

-- Edited by Jaahn on Friday 15th of May 2020 09:29:08 PM

-- Edited by Jaahn on Saturday 16th of May 2020 09:13:24 AM

markf · Senior Member

Getting rid of interference of any type can be an exercise in frustration. Ask anyone who's into amateur radio and they'll almost all have tales of the "day I almost became a drug addled, alcoholic, axe wielding, radio wrecker".

The steps to getting rid of interference are working out what sort of interference it is. Hi frequency, low frequency, impulse, etc. How is it getting into the TV ? Is it coming in via the power cord or the antenna ? And most importantly, where is it coming from ?

There are lots of variables when it comes to chasing down interference - far too many to address in one post. In your case I reckon I'd start looking at the fan that causes the interference when you switch it on. To tackle the antenna system, power cables, etc. is only avoiding the issue. Treat the problem at the source - the fan first.

Bicyclecamper · Guru

I have a Tv , on 12 volt,it was originally being used on 240 volt but we got an amplifier and 12 volt lead from Jaycar . Have never had a problem with it since we have had it or c.van, it is an Changhong, or chonhing, or ghang ching, actually don't know what it is, would have to go over to the van to find out what it is, but that is beside the point. The last van and tv we had, I built my own aerial, so it would fold up an pack away easily, it worked like a charm, until we stayed at the Eucla, then we could only get SBS, but we were camped in the bush a bit out of town, so I buried most of the coax cable into the ground by 6 inches, and I got 2 extra channels, I think it stopped a lot of interference. But this does not enswer your question I don't think.

oldbloke · Guru

Interestingly. Sometimes after the heater fan at home stops the digitizing continues. If i remove the arial plug from the wall and plug back in the picture comes good.

Aus-Kiwi · Guru

Twisted wires act as shield . The earth - wire around the positive + wire .

oldbloke · Guru

Aus-Kiwi wrote:
Twisted wires act as shield . The earth - wire around the positive + wire .

Pretty sure the interference is from the arial. But will try that

Ozlad · Member

I put one of these to help with interference with our portable 12v radio, while it helped it didnt completely eliminate it,
www.jaycar.com.au/u25-ferrite-voltage-spike-protectors-noise-suppressors-each/p/LF1290