Railfan Technology > Scanner interference from car

My 2016 Subaru Outback causes interference on 160.875 with different scanners and antennas.When I turn the engine off it works fine! I also have a problem at home with our new heat pump that causes interference on 160.515.

It's a fairly common problem. Scanners are often very poor at blocking interference. Interference can be introduced a couple of different ways. If the scanner is getting its power from the car (cigarette lighter outlet or hooked directly to the car's electrical system), installing a line filter on the power supply may help. I use an inline filter from Powerwerx for that. They are around $20 and will do an OK job most of the time.

If the interference is present with a portable or any radio in vicinity of the vehicle, that's a much bigger problem. Something in the vehicle's electrical system is "dirty"--spewing out a lot of RF interference. Fixing that usually entails figuring out what component in the vehicle is putting out the RF interference and replacing it. Modern vehicles have a lot of electronics, so sleuthing out the culprit can be difficult. Common things are the voltage regulator (usually contained within the alternator on most modern vehicles), the alternator itself, electronic control modules (ECM), ABS controls, lighting/security systems, etc. If one of those things is the culprit, replacement is often the only option--and expensive.

One other note: if the RF interference stops when the ignition is shut off, that's great, but if it doesn't, then it probably is an electronic component that is running even when the ignition is shut off. Then there are things that run for awhile after the ignition is shut off before they turn off--for example, interior or exterior lighting shut off delays, etc. A key diagnostic technique is to ascertain when the interference starts and/or stops.

I go back to my often posted admonition about scanners vs. commercial radio models. Most good commercial model radios are MUCH better at handling the type of RF interference commonly found in vehicle electrical and electronic systems. That said, if the vehicle is causing RF interference to a commercial radio (and I've seen plenty of vehicles that have), then there is usually something significantly amiss somewhere in the vehicle's electrical system.

As for interference from things like the heat pump that the OP mentions, all types of appliances are SUPPOSED TO comply with Part 15 of the FCC regulations prohibiting RF interference emissions. In reality, few comply because there is almost no enforcement of the rule. About the only option there is replace the offending appliance or electronic components therein--expensive, or to use a radio (probably a commercial model once again) that is better at rejecting the interference.



Edited 1 time(s). Last edit at 05/04/18 07:20 by WW.

Putting the scanner antenna on the roof may prevent pick up of the noise source. Chances are the car components are working as designed, so there is nothing to fix to reduce the interference. This sort of thing is very common these days. It isn't worth mucking around with complex systems and voiding warranties to attempt to correct it.



Edited 1 time(s). Last edit at 05/04/18 09:33 by radar.

I get static on my scanner from my camera!

I installed LED driving lights on my truck, whenever they were on the FM radio was solid noise no matter what station. These were the type that had a fan on the back for cooling. They made it to the garbage can within a week.

radar Wrote:
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> Putting the scanner antenna on the roof may
> prevent pick up of the noise source. Chances are
> the car components are working as designed, so
> there is nothing to fix to reduce the
> interference. This sort of thing is very common
> these days. It isn't worth mucking around with
> complex systems and voiding warranties to attempt
> to correct it.

Trying to receive anything on a rubber ducky from the inside of the vehicle is usually very unsatisfactory. The radio reception is already compromised by the Faraday cage created by the vehicle body and, yes, RF interference from vehicle electronics may be amplified. Again, it just depends how bad the interference is--I've seen RF interference from a supposedly "healthy" vehicle's electronics peg an RF meter for 20 feet around it.

Your fuel pump is what is causing the interference.

Posted from iPhone

trkinsptr Wrote:
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> My 2016 Subaru Outback causes interference on
> 160.875 with different scanners and antennas.When
> I turn the engine off it works fine! I also have a
> problem at home with our new heat pump that causes
> interference on 160.515.


Finding the source and preventing noise and intermods can be very complex. A typical hobby scanner will be very challenged in most situations.

Just for clarity, the interference is tripping the squelch circuit and perhaps the FM demod circuits at a combination of IF and LO frequencies that coincide with that frequency on the front end of the scanner. Whatever is being generated by the car or heat pump is most likely not at radio frequency. The problem noise could be at RF frequencies but is usually relatively broadband so not likely to show at only one or two RF channels. There may or may not be an audio sound from the radio that could help sort out the source.

My 2010 Subaru is very touchy inside as well, more touchy or 'hot' as I turn on the lights and the windshield wipers, obviously noise on the DC side of the car. The Yeasu radio I'm using is battery powered so that's one clue, when I touch the radio knob, any dashboard controls the steering wheel buttons or put my hand near the radio, it opens the squelch with constant noise or sometimes a data noise. In those old days the Distributor, points and spark plugs could be heard over a scanner, now it's the car's data bus. If you look under the driver's seat (in a Subaru and maybe other cars) there's basically a computer, maybe it's called a controller or whatever but it has all the noise generators of a computer. One way to gain better characteristics of the noise is to turn the car off, knowing that it doesn't all turn off at the same time. The aforementioned computer usually stays on for quite some time and could turn off in functional sections. The alternator and any motor noise should go away though.

The car windows ruin the absolute advantages of a Faraday cage. Plenty of RF gets in and out through the windows. Not to mention modern cars are not completely metal, or even completely continuous metal panels. There's plenty of weather or vibration gaskets and plastic covered holes in modern cars. There's also poor grounds that work fine for a typical car but are still conducting noise around the inside of the car, including that data 'noise' that goes to different parts of the car. It may well meet an RE/RS spec for the car to function but not necessarily for a hobby radio.

Clearly a well chosen high end radio should be able to handle or reduce the intrusions into the radio itself. Usually with additional downconversion and filtering, also shielding around sensitive circuits ( Faraday cage again ). The ultimate is a steel case, that Faraday idea around the radio itself, properly grounded to the metal car frame.

Let us know how it works out.

asull85 Wrote:
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> Your fuel pump is what is causing the
> interference.

I'm fairly certain that's what caused the interference on mine.

Interesting thead. Whilst railfanning in the States, years ago, my EOS 5 film camera always caused interference. BUT - my friends didn't. Spooky or what!! chris k.

asull85 Wrote:
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> Your fuel pump is what is causing the
> interference.
>
> Posted from iPhone

That might be one source, but modern cars are full of microprocessors. The engine control unit (ECU), the body integrated unit (BIU), ABS brake and stability control, air bag control, collision avoidance, blind spot detection, entertainment system, navigation, etc. I'm sure I'm forgetting some.

Even the simplest car model has several microprocessors, all of which can radiate RF.

"Clearly a well chosen high end radio should be able to handle or reduce the intrusions into the radio itself."

Over the years, that has been about the only relatively sure-fire solution to RF interference. Even that may not always work, but it is usually the most effective. Good quality amateur radios have gotten a lot better at rejecting RF interference, but even they have issues with it. Some years back I had to junk what was otherwise a pretty good amateur mobile radio because it simply could not reject RF interference, even with all kinds of filters, etc. In mobile radios, I essentially use commercial equipment exclusively, and their good intermod rejection ability is a major reason.

One other note: many commercial radio systems are set up with some sort of tone squelch codes (e.g., CTCSS codes for analog, RAN codes for NXDN digital) that are designed to only allow the squelch of the radio to open if the correct code is contained in the signal received. The helps control a lot of unwanted RF opening the squelch on the radio, but it may not prevent RF interference from garbling up a desired, but weak signal trying to get into the radio. In most railroad radio operations, tone squelch is not used because of the fact that railroad equipment may inter-operate on other railroads.

Good radio design can reduce interference from sources that are not on the desired channel. Broadband noise that is on the desired frequency is going to interfere no matter how good of a radio it is.

When I was working for TxDOT here in Austin, we had radio interference issues with 2 major manufacturers of the heavy duty trucks the state of Texas purchased.

It took us over 1.5 years working with the manufacturers for them to solve the problems which came from the multitude of on-board vehicle computers.

There are also federal standards, don't recall that vehicle manufacturer must meet for vehicle interference for two way radio systems. I have had some ham friends bring this up when they had interference and once they showed them the documents, they acted quickly to resolve most if not all of the radio interference issues.

However, using an outside antenna is a must start to prevent interference to the radio and then work forward from there.

Also had issues with the cars and other vehicles.

We mostly purchased Motorola high end low-band and VHF high-band radios. Motorola helped a little but we ended up by hiring a specialized company that had a very large quite chamber and we could drive the vehicles into the building.

The vehicle manufacturers participated in the testing. Numerous high way departments were reporting the same type issues. We also used the manufacturers testing facility.

This resulted in major design changes to the on-board computer systems, adding more shielding, and moving the frequency away from the public safety radio band.

Took lots of effort but now, whenever TxDOT purchases a new vehicle, the manufacturer supplies data about radio interference.

Good luck

Pat
WA5VRO
South Austin, TX

radar Wrote:
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> Good radio design can reduce interference from
> sources that are not on the desired channel.
> Broadband noise that is on the desired frequency
> is going to interfere no matter how good of a
> radio it is.

Sadly true. Vehicle electronics certainly can do this on occasion. I've also seen interference from stationary sources that goes off the chart. In one instance, there is a spot way out in the country a few dozen miles from where I live where RF interference from some stationary source is so bad that it will "jam" a commercial digital radio that I use for nearly 4 miles of highway. It goes on because the FCC essentially has no budget resources to enforce the RF interference rules outside of the metro areas. The nearest FCC office to me these days that could send out a field unit to check an RF interference complaint is 800 miles away.



Edited 1 time(s). Last edit at 05/05/18 19:58 by WW.

WW Wrote:
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> radar Wrote:
> --------------------------------------------------
> -----
> > Good radio design can reduce interference from
> > sources that are not on the desired channel.
> > Broadband noise that is on the desired
> frequency
> > is going to interfere no matter how good of a
> > radio it is.


> ... there is a spot way out in the
> country a few dozen miles from where I live where
> RF interference from some stationary source is so
> bad that it will "jam" a commercial digital radio
> that I use for nearly 4 miles of highway.
...


That happens to my Yeasu near Orin Junction in Wyoming, on I-25 but all the way to the ridge on SR-18 near Shawnee Junction. Inside the car, outside the car, car on or off. With the two junctions there and the channel changes it's not a good spot for no radio monitoring.

Probably all the repeaters on the ridge to the west and then another installation of them closer to Douglas. Must be a sweet spot in the topology for all the repeater companies to have built them there.



Edited 1 time(s). Last edit at 05/05/18 20:19 by TCnR.

I switched my 5/8 wave antenna for the 1/4 wave that was mounted on my 2016 outback and that did away with the interference on 160.875!

trkinsptr Wrote:
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> I switched my 5/8 wave antenna for the 1/4 wave
> that was mounted on my 2016 outback and that did
> away with the interference on 160.875!


Just for clarity, this is a very common phenomena, although agreeably less than ideal. There's lots of technical reasons that 'could' explain it but that would need all sorts of additional info. Sometimes a 5/8 just doesn't work out, sometimes it does and is often worth trying out.

I cleaned off built up crud on my 1/4 wave antenna and now it picks up 160.875 without interference!