Help needed - Vehicle aircon system causing VHF RFI

[VK5MLB]

I am hoping someone may be able to provide me with some advice on how to get rid of some RFI caused by the Aircon / Heating system in my 2005 Hyundai Terracan 4wd.



The interference seems to oscillate up and down the VHF band lasting for about 10 or 15 seconds on each frequency before moving somewhere else in the band. It can be heard on the Uniden scanner as well as the 2m/70cm Wouxun radio. The signal strength is reasonably strong, really too strong to just remove with the squelch.

It seems to change frequency when I change between the recirculation and fresh air mode on the vehicle heating / cooling system. It also doesn't matter whether the fan is actually on or not, you still get interference when the unit is just sitting idle. Changing other functions on the unit doesn't seem to change the level of interference.

I am a bit stuck as to what to try, I did put some clip on ferrite cores onto the cables coming from the rear of the unit, but that hasn't changed anything. My ultimate solution will be to try another Aircon unit in the vehicle, but that is a last (and costly) measure. The other option it to have no VHF in the car, but that is also undesirable.

Has anyone seen anything like this before ?

Thanks

Matt - VK5FMLB

[ZL2WHO]

Hi Matt. This is a stickler, Id be looking for a SWM power supply inside the electronics. Sometimes the fan speed regulator
is switched. Can you get a circuit diagram of the electronics for the Aircon ? id be letting the car company know about it.

[VK3RX]

You could try contacting Hyundai Australia. You would not be the first in the world installing a VHF radio in that model or with that system, and they may have a fix i.e. a suppression kit.

I've had similar issues in the past with a couple of overseas manufactured vehicles, and while in one case it took some time for the local branch to get a response from Japan, eventually a kit was sent out and the problem fixed.

[VK5MLB]

Thanks guys, I will fire off an email to Hyundai and see what comes of it.

Matt

[VK5MLB]

I received an email reply from Hyundai, it seems that they say they have not seen this problem before and are unable to provide any suggestions.

It looks like I am back to square one.

If I knew that another Aircon unit from a similar vehicle would fix it I may look at that, but I can't really be sure that will do it.

Hmmmm, what to do??

[VK2CSW]

Hi Matt

Your description of the interference changing frequency makes me think that an A/C unit wouldn't be at fault. Exactly why do you think it is related to the A/C.

When you say frequency, I assume you mean the RF frequency, not the audio pitch. If so, I would immediately think Engine Management, the processors in them little buggers can be a bit noisy, does a Terracan have that sort of engine management (2005 model - I would guess it would) maybe you could screen it?

Colin

[VK5MLB]

The reason I thought it was associated with the Aircon unit is because changing the setting from recirculation to fresh air causes the frequency (RF) to alter.

If you have a look at that video you can see what I mean (just click on the picture), when the noise starts the Aircon unit is set to fresh air - then I change to recirculation mode and it changes frequency - then back again and it appears on another VHF Marine frequency. This was without the vehicle engine running (I believe that rules out the engine management system).

It seems to pop up right across the VHF spectrum at various times, making the scanner, fire brigade radio and 2m Wouxun unusable sometimes.

[VK3RX]

Don't give up on Hyundai. Their local customer service office here might not have heard of RF interference, but the head office in Korea certainly has. Ask them to escalate the problem to Korea.

Some info from the ARRL:

Hyundai has an extensive EMC test facility at its factory in Korea. They have not experienced many problems with properly installed, medium-power transmitters. Their customer-service engineers have been able to work successfully with their dealers to straighten out any problems that have been encountered. They do not have any published installation guidelines, but suggest that a proper installation would keep power and antenna cables well away from the ECM and its wiring, obtain power directly from the vehicle battery and ensure that the antenna were properly tuned and installed, well away from the ECM. The ECM is located just behind the kick panels on the left or right side of the vehicle. Customers who experience problems should first carefully evaluate the installation, then, if necessary, contact their dealer. Dealers have access to Regional Offices and the National Technical Services Department for assistance in resolving customer problems.

And some links with general installation info below. Suggestions re routing wiring and antenna cable clear of vehicle wiring and modules as far as possible are good ones. Somewhere I saw a suggestion that where possible cross power and antenna cables 90 degrees to vehicle wiring to minimise interaction. Not always possible of course.

Is the interference still there when the antenna is disconnected? That can help to isolate whether it is coming in via power cables or antenna pickup.

http://service.gm.com/techlineinfo/radio.html
http://www.k0bg.com/

[VK2CSW]

The reason I thought it was associated with the Aircon unit is because changing the setting from recirculation to fresh air causes the frequency (RF) to alter.

If you have a look at that video you can see what I mean (just click on the picture), when the noise starts the Aircon unit is set to fresh air - then I change to recirculation mode and it changes frequency - then back again and it appears on another VHF Marine frequency. This was without the vehicle engine running (I believe that rules out the engine management system).

It seems to pop up right across the VHF spectrum at various times, making the scanner, fire brigade radio and 2m Wouxun unusable sometimes.

Still could be engine management, despite the name they tend to run pretty much every thing, even when the ignition is off...
So when you activate a dashboard control, the ECM can get involved - thus the RFI you are seeing - I have to admit I am just thinking "out loud" here.

[VK2HRX]

....recirculation to fresh air causes the frequency (RF) to alter...

This (recirculation to fresh) isnt a function of the aircon unless this vehicle is set up in a different way to any others I have seen over teh years.

Compton
VK2HRX

[VK3RX]

I assume what the button(s) are doing is simply opening and closing a vent (and if the engine is off, that is probably all that is happening). In my vehicle, that function and just about everything else is controlled by "the computer" (called ETACS ECU system in my case). When you press a button (other than one for a switch that is clearly a click on click off type) it is a software function i.e. you are telling the box you've selected that particular function.

You don't mention how you have your radios wired in. If you've tapped into something else or even run leads back to the fuse box to a live point, there could be crud on the line. Try leaving the radios mounted where they are, and running power leads direct to the battery, out the door if necessary just for a test, and see if the problem is still there. Be careful about polarity and make sure you have a fuse in the cable(s) .

I once had an FT690 running off either the cig line or something else I found under the dash, and there was low level noise (not alternator whine) on tx - rx was fine. I ran leads direct to the battery, and problem solved.

[VK5MLB]

I had another look at this today, no solution yet but what I did find was that the interference is almost certainly coming from somewhere inside or very close to the Aircon control unit.

With the Wouxon handheld running on battery power I was able to walk around the vehicle and still receive the interference at a reasonable signal strength - I think this rules out dodgy wiring to the radio.

With some attenuation I found that the signal was definitely strongest when the antenna was touching or very close to the Aircon control system, so it is something from fairly close to that unit.

I also found that the noise was dropping about 12.5khz every 10 seconds, this was on some 156mhz frequencies.

This video is not great quality but you will get an idea on what is going on.

http://s152.photobucket.com/albums/s185 ... 032011.mp4

I agree that the pushing of the recirculation / fresh air switch is linked to a processor somewhere (probably part of the Engine Management system), this then operates the motor to open or close the vent. The signal is not very strong in the location where that motor and vent is located, so I believe the processor is more likely the cause.

Still open to all suggestions ...

Matt

[VK2XDE]

Hi Matt,
The noise I hear in your first video appears to be ignition noise or injector noise.
You appear not to have the squelch (Mute) fully open in your video and it appeared to close the mute when the noise level dropped slightly when you pushed the buttons.

If it is ignition noise or injector noise the ticking noise will increase in frequency as the accelerator is pressed and engine revs increase.

The noise will most likely be getting into the radio via the DC power lead and /or the aerial. Try disconnecting the aerial at the radio.
Where is the aerial mounted on the vehicle?

If you still have the noise without the aerial connected use a 12 volt gel cell to run the radio (without the aerial). Has the noise reduced in level?

If the noise is coming in via the aerial, plug an aerial in that is not attached to the vehicle and move it away from the engine compartment. (behind the vehicle)

Does the noise exist without the engine running but with the ignition on and the air conditioner fan on?

Awaiting your reply.

Steve VK2XDE

[VK4APN]

If you still have the noise without the aerial connected use a 12 volt gel cell to run the radio (without the aerial). Has the noise reduced in level?
Steve VK2XDE

I had a similar problem on my Forester - I gave up trying to find the source of RFI. I ended up using a good compromise setup - I mounted the main part of the IC208H on a board together with a 7ah gel cell that is charged via the 12v utility socket thru a high power schottky diode to the gel cell battery. So the radio is powered via the 7ah battery directly & charges up whenever I am driving. The board is mounted under the drivers seat. It works for me.
Good Luck
Paul vk4apn

[VK5MLB]

Thanks guys, the noise is still present with the engine off but the ignition on.

It is present with the handheld radio running on a battery with just the whip antenna connected. I would assume that would rule out the noise getting in through the power or antenna cable. I feel that it is actually being radiated from the CPU that runs the A/C unit.

Unfortunately the noise is still about S7 on the handheld standing at the back of the car, so moving the radios around inside the vehicle doesn't seem to be a likely solution either.

The way that it oscillates through the band is annoying as well, you can't just lock out a frequency because it ends up pretty much everywhere at some stage.

Quite frustrating...

[VK3RX]

When you can hear the crud on a handheld outside the vehicle without the engine running ..... I'm out of ideas.

Parallel to suggestions here, pursue Hyundai, ask them to refer the problem to Korea. Outline the problems in basic english (maybe short dot points), tell them it is a commercial VHF band two way radio you are installing, the vehicle is generating high interference to the extent that operation of VHF high band two way radios is impossible with this model vehicle etc. i.e. talk it up a bit. Can't hurt ....

[VK5ZD]

Hi

I get some noise from the electric fuel pump on my car (Ford, not Hyundai), although this only affects HF in my case. The electric fuel pump is inside the tank which slightly complicates matters. While this might not be related to your problem, I wanted to mention that the noise generated by the pump can be heard on a receiver that's brought near any of the wiring in the car. i.e. the problem might not come from the part of the vehicle where it appears to be strongest.

Secondly, a frequency shift when you operate the ventilation controls might just be due to the minor change in the battery voltage when the vent motor(s) operate.

73
Iain

[VK2DVZ]

As an aside to the supposed A/C noise or similar, I had a Toyota Camry V6 sedan that gave off lots of noise, mainly at HF frequencies, that was fixed ultimately with the installation of multiple tubular ferrite core - but not the split type, (2 or 3 if I remember correctly). I was installing an IC-706M2g HF rig and a Turlin Outbacker whip on the tow bar at that time.

The noise was found to come from the electric fuel pump, buried inside the fuel tank.

I obtained Ferrite cores from RF Industries in VK3 land. The core mix of the ferrites was suggested so as to offer maximum suppression at the worst affected frequencies involved. I remember I was asked to determine and and note the signal strength of the interference on each of the amateur HF bands, which I did, then forwarded the results on to RFI. They supplied the cores that offer the best suppression.

I had to remove the back seat to gain access to the multiple wires running to/from the tank. I had NO spare length of wire to play with, so I cut all wires and spliced in additional wires of same wire diameters that had been pre-wound through the 2 or 3 cores, then soldered the whole lot into place.

I worked like a treat - noise virtually gone!

Good luck solving your noise problem too Matt.

Ross.

[VK5MLB]

Thanks Ross

I think the next step is to pull apart the dash and take out the Aircon unit, that way I can have a good look at it and possibly put a number of ferrite cores on the wiring associated with it. It's not going to be a fun job but one that I think I will need to undertake if I want any chance of solving this.

With the amount of RFI crud this thing is generating I really would have thought Hyundai would have had more of a clue about what is going on, there must be other people out there with a VHF radio in a Terracan. I think I will be escalating this to the Korean gurus to see what they think.