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Fredk20716 · 05-13-2018, 11:34 AM

I have an inexpensive EBay wireless backup color camera I installed wiring to one of my marker lights. It worked great but only with the lights on. I have since added a TPMS another inexpensive EBay purchase and experience interference (snow) over the camera monitor even with the TPMS off. Does the TPMS interfere with the camera or could it be something else? The interference is with the engine on/off.

A quick Google search indicated that if I add passive noise filter it may eliminate it.

https://www.youtube.com/watch?v=-GsqtuS7PUo

ANYONE HAVE A FIX FOR THIS ISSUE? Thanks.

uncledon · 05-13-2018, 11:58 AM

So do I understand correctly that there was no interference when first installed, but then after the TPMS install you noticed it?

If so, and if the interference is present when vehicle is not running, and TPMS is off, then try removing batteries from all TPMS sensors. Possible that there is something going on there as the sensors emit signal continuously when batteries are installed. It can't be noise from vehicle if it's not running.

Mudsock · 05-13-2018, 01:01 PM

You need to determine if the noise is coming in through the power line, or through the RF channel. It may well be that the TV receiver is receiving an interfering signal from the TPMS transmitters, especially if they are operating on the same band. The transmitters are at the tires and turning off the TPMS receiver does not stop all sources of potential interference from the TPMS system. By turning off the receiver you have likely eliminated it as the noise source. It would certainly be eliminated if you remove power from it. Any clocked digital circuit is a source of RF radiation, although the radiation level of some are so low as to be negligible. Engine and transmission controllers are terrible radiators at different frequencies and often under go one or more design turns to clean them up. They ALL still radiate and can cause interference. The design goal is not to interfere with other systems on the vehicle. Add a new system, as you have, and the potential for problems recurs. But turning the engine off long enough for them to shut down (maybe more than a minute - the have a list of things to do at power down) eliminates them as a source.

When you power more than one device on a run of wire, the voltage drop on the wire is the sum of the drops caused by the current drawn by the various devices. If one device is switching on and off, it would subject the other devices to a common mode voltage drop and could be a source of common mode noise. This type of noise could potentially be reduced by a power line filter - an inductor. The core material of the inductor has a range of frequencies at which it is useful. Interference coming in the power line can be at RF frequencies. I would use a 12V gel cell battery as a power source for the camera and then the receiver to eliminate common mode noise as the problem. Batteries are a clean source of power when they only power one item. Add the second and common mode noise can develop. You could use 6 D cell batteries as a source for a short period of time.

The ARRL arrl.org has a book, “Radio Frequency Interference- How to Identify and Cure it” ($4.00). It has some good information.

These types of problems consume a lot of engineering time and money to resolve. Low end equipment often lacks adequate internal filtering. Sometimes the entire responsibility for the problem rests with the device receiving interference. Phonographs, CD players and public address systems are not supposed to receive radio signals, but some do. The fault is not with the transmitter in such a case.

It could be that the signal coming from the camera transmitter is not strong enough. That causes snow on all analog TVs. Move the camera much much closer to test this. Is the voltage supplied to the camera really what it requires. Measure it. Common mode voltage drop could be the problem, especially when the battery is low, or the alternator is not boosting the voltage.

It could be that feeding the receiver with a twisted pair would cause the power line to stop being as susceptible to RF energy. The power line can function as an unwanted antenna for transmitting ore receiving RF energy. A twisted pair is simply a positive battery wire twisted together with the return, or ground line. Six or eight turns per inch is common. The technicians used to pinch two wires in the chuck of an electric drill and let the drill do a clean job of it. Twisted pairs are often used in automobiles to resolve noise issues.

Waiter21 · 05-14-2018, 06:52 AM

I had the same problem.... I installed an inexpensive wireless camera on the back of my Mirada.

I installed TPMS sensors in my ACME dolly wheels and the rear wheels of my Camry. They were intermittent whenever I turned on the rear camera, that was wired to the rear clearance lights.

I finally decided to run a coax cable for the camera and do away with the wireless.. The Camera now worked perfectly, and no more problems with the TPMS..

wa8yxm · 05-14-2018, 08:15 AM

TPMS uses radio transmitters.. Wireless camera uses Radio transmitters. IT is indeed possible they are using the same channel and thus will cause mutual interference. Suggest wired camera.