Defender (Puma) radio interference

[patto1]

My 2010 MY Defender electrical system makes massive amounts of electrical interference on the broadcast band as well as on Flying Doctor HF frequencies. In fact it is impossible to use the HF Flying Doctor frequencies whilst the engine is running. I believe this problem is not just on my vehicle but on all Pumas. I have contacted Land Rover AU and they do not have any solutions. Land Rover UK tell me that they have done noise reduction on the military version but are not willing to give out any of the information.
Has anyone had any experience in reducing the HF noise on the Puma?

[Symo]

I have no idea but could only be the alternator, couldn't it? Had it full of mud?

Try a snubber on it, cap to ground and see if that helps.

[wrinklearthur]

Hi patto1

Before you start fitting noise suppression components on your vehicle, I would try and find the source of this noise.
A fairly easy way of doing this is, grab hold of a pocket AM radio ( that works ), then turn it off the stations into a quiet part of it's AM band .

Turn the volume up until you can just hear the hash noise in the radio then ease it back a little on the volume until its a bit quieter.
With this set, start the Land Rover and turning around the radio about itself you will find that the noise the Land Rover makes in the radio will vary in strength, walking around the vehicle you can then use this effect to pin point the nosiest parts, if the noise coming from the radio is too loud, reduce the radios volume until it is usable and continue working.

Take particular note whether it is the wires, for example: that are leading into a computer or the say, wiring feeding the injectors.
Other noise sources can be voltage regulators or the alternator, etc.

Let us know asap on this thread then we may be able to offer some suggestions as to how to help.
.

[numpty]

This is not unique to the Puma as my Td5 causes the same interference with the HF. I believe other electronically controlled diesels do similar things

[ThorneGator]

If you haven't found the source yet, maybe try this.....

Long story-made short, a patient I worked with, worked as a profession doing just this, finding and repairing the interference grounding issues on vehichles. By chance he mentioned that they usually started with the exhaust system. Since the exhaust system is attached by rubber (insulation) hangers in all places except where it runs from the exhaust manifold, it can actually act as an extra antenna. They would ground the tailpipe back to the chassis with a small piece of wire to see if that stops it.

Hope this helps, I'm just the messenger.

[wrinklearthur]

Hi All

I agree with the grounding of panels to quieten RFI ( radio frequency interference ) especially the bonnet or doors.

Using capacitors, ( they stop direct currents and pass alternating currents, ) are sometimes a better way to go, I say this, as earthing a exhaust pipe to the chassis using a earth strap, could cause some weird fault, if the vehicle's earth bond between the chassis and motor was to come a bit resistive in it's joints.

I have seen RFI in a ( EFI ? not sure if this is the correct description for this truck ) Mack truck become worse when they tried to quieten the RFI.
I didn't agree at all with the other technicians 'fix', He desensitised the VHF two way radio by internally adjusting the squelch setting, this reduced it's range considerably!
Shielding wrapped around the wiring loam and then grounded at the best distance from the noise source would have been the best solution to this RFI problem.
.

[Davo]

Shielding wrapped around the wiring loam

For peat's sake, that's very earthy . . . sorry, spellcheck off . . . anyway, I've read a lot about this over the years, but do you know - radio types never really explain anything!

So what would you use as shielding? For instance, if I started shielding my distributor-to-coil wiring, (the low tension wires, that is), what would be the best stuff to use?

And what would you use as a capacitor? I notice the one next to the electric fuel pump on my carbie Rangie looks a lot like the condensor from a points distributor. Would a condensor, (easy to buy and cheap), do the job or is it more specialised than that?

And something else I read the other day said that braided copper is best for grounding body panels as the RFI travels on the outside of a cable. Is this right? And it sounds like ideally you need one of these straps for every door and the bonnet of a vehicle?

(And pardon the partial hijack, though it is on topic at least.)

[Bushie]

This may give some ideas

Common rail diesel* Interference suppression (http://www.amalgamate2000.com/radio-hobbies/radio/common_rail_diesel__interference.htm)

Martyn

[wrinklearthur]

Hi Martyn

I have just seen your posting. That is a well thought out explanation of how to systematically work the problem of RFI.
I had already drafted this posting but had a lot to delete and add still so I hope no one takes an exception as I didn't have time to rework it.
Here is my post anyway.


For peat's sake, that's very earthy . . . sorry, spellcheck off . . . anyway, I've read a lot about this over the years, but do you know - radio types never really explain anything!
Hi Davo

I wonder sometimes if the best way is not to explain ????

For instance, how do you explain the damage to coax I have seen, that was caused by a lighting strike?
The coax was cut into 2 metre lengths between the TV aerial and the house !
The reason this damage was caused in the first place was the lack of a suitable earth and lightning rod at the aerial mast.

How to explain the couple of dozen cuts caused by the intense heat ( think, lots of power in Mega Watts ), can also be used to think about where the earthing on vehicle shielding should be.
The distance between the cuts in the coax is the clue and knowing that duration or pulse of a bolt of a lightning only exists for a certain time, sets up what is called a standing wave. But I am not going to write up a thesis on standing waves from Lightning strike, from a four year course at university and post it here on this forum. So for those that what to know more, I suggest that you read up in theory books designed for training radio technicians.


So what would you use as shielding? For instance, if I started shielding my distributor-to-coil wiring, (the low tension wires, that is), what would be the best stuff to use?
Is it the low tension wire the one that is causing you trouble?
If you need to, I would use what ever is at hand, if you work for a multinational manufacturing plant, the job would get exactly what is required. Out in the scrub you could try stripping the inner out of some large coax and use the sheath and the braid sliding that over the wire radiating the electrical noise. A bit of knowledge of antenna theory is also handy at this point, so the earth can then be attached to the improvised shield, where it would be the most effective.


And what would you use as a capacitor? I notice the one next to the electric fuel pump on my carbie Rangie looks a lot like the condensor from a points distributor. Would a condensor, (easy to buy and cheap), do the job or is it more specialised than that? have a look for a impedance chart for capacitors and choose the size from that. you will need to know the frequency band that the noise is a problem in. A previous posting I did warn not to try adding on capacitors haphazardly on, especially electronic devices such as car computers that have pulsed information on those wires.


And something else I read the other day said that braided copper is best for grounding body panels And it sounds like ideally you need one of these straps for every door and the bonnet of a vehicle?
Yes, try a clip lead first and if it does make an improvement then go to something like those grounding straps for the mechanically longer life they can deliver and do try one panel at a time.

RFI travels on the outside of a cable. Is this right?
As a rule of thumb, HF travels through the conductor and signals in the UHF range travel on the surface of a transmission line or aerial element.

(And pardon the partial hijack, though it is on topic at least.)

.

[Davo]

Martyn, thanks for that. The last paragraph lost me, but I could follow the rest, though I don't quite get why you'd use the large ferrite beads on some wires and the braided stuff on others.

I see that guy was another ham radio man. These are always the ones who write long articles that can only make sense to each other as they are all real enthusiasts. For me, I just want RFDS and VKS-737 to be as good as possible, and I know it doesn't take much to make a signal worse than it could be.

And Arthur, a thanks for going to the trouble to write that up, just as I was writing this, I see. That makes a bit more sense of things.

Anyway, I think this should answer the original post, I hope!

(And now to post the antenna mounting question that's been bugging me for days . . . )

[patto1]

Hi All,
Thank you to all who sent comments (and tried to help). Bushies reference to another article was a good start. Since I have had the vehicle I have bonded the exhaust pipe in three places over its length, Bonded the rear door and bonnet .... to no effect. The alternator has not been in the mud! When I go over the vehicle with a hand held radio (as wrinklearthur suggests) ..... with the ignition key turned on (but the engine not started) I get lots of noise. I am not sure if the injectors are firing at this point? (anyone advise on this). The noise is just as bad at the back of the vehicle as at the front .... maybe the fuel pump is making noise?. Someone on another thread suggested the noise could be carried to the rear of the vehicle via the wiring to the lights, demisters etc.
I looked for the fuel pump thinking that may be the culprit .... maybe it is in the fuel tank? ... in which case it will be difficult to put a ferrite on the wires (anyone got a circuit diagram of this bit of the wiring?) When I start the engine there is more noise .... and when travelling along the road the noise changes with throttle setting .... maybe still the fuel pump?
What I cannot understand is a manufacturer making a vehicle that emits so much noise ... to the point where the AM radio (fitted at the factory) is nearly unuseable. I have had a few other diesels ... non were anywhere near as bad as the Land Rover PUMA Defender. (Holden Rodeo ... no noise) (Mercedes ML ... no noise) ... the same HF radios were installed in those vehicles and there was no problem. ... those manufacturers obviously have technical people who are on top of their game. Why Land Rover UK do not want to help owners reduce the interference is difficult to understand. They claim that their military versions are "quiet" but are unwilling to give any clues on how they did it.
Please keep your ideas coming ... they are gratefully received.

[Davo]

Well, as you can see in that link, there are other vehicles with your problem. And don't feel too bad - there was someone who wrote an article for the VKS-737 newsletter about how in their car (I've forgotten the make) the engine would just stop when they hit the HF transmit button! Apparently this was quite exciting on the highway.

They had to go to a specialist who added some bits and the owner didn't know exactly what they were, but they worked. Which just goes to show.

Electronic vehicles are what we're stuck with. I wouldn't mind at all, but a problem like yours just shows how badly designed they are when there's no thought given to things like this. This is why I've stuck with non-computerised Land-Rovers.

Since this is a common a problem, just keep looking at what others are doing. Remember the point is to be methodical and to take one step at a time, much as with any other troubleshooting. Go by the articles that others have written and try and isolate one system at a time, or you'll just get confused.

[Davo]

Just looking at the photo of your antenna mount that you posted on my antenna thread, (thanks, by the way) - how have you grounded it, given that it's sitting out there behind the spare wheel?

[wrinklearthur]

When I go over the vehicle with a hand held radio (as wrinklearthur suggests) ..... with the ignition key turned on (but the engine not started) I get lots of noise. I am not sure if the injectors are firing at this point? (anyone advise on this). The noise is just as bad at the back of the vehicle as at the front .... maybe the fuel pump is making noise?. Someone on another thread suggested the noise could be carried to the rear of the vehicle via the wiring to the lights, demisters etc.
I looked for the fuel pump thinking that may be the culprit .... maybe it is in the fuel tank? ... in which case it will be difficult to put a ferrite on the wires (anyone got a circuit diagram of this bit of the wiring?) When I start the engine there is more noise .... and when travelling along the road the noise changes with throttle setting .... maybe still the fuel pump?

Please keep your ideas coming ... they are gratefully received.

Hi Patto

I'm pleased you tried that search with the AM radio, as you have now found, the vehicle wiring does radiate the radio frequency interference, so do that test with your AM radio again, the same as you did before, with the switch on and without the motor running. Only this time, pull out one fuse at a time out of the fuse box, do your test then after replacing that fuse, move to the next fuse. Without power the device that was making the noise would be quiet, take note of any change in the noise from your pocket AM radio and write down your results then let us know what you have found.

As I said in the previous post, don't try and add so called fixes haphazardly, You can chase your tail forever doing this, it's best to find the source / sources of the noise, before adding noise suppression.

So Patto, battle on and I will keep a eye on this thread to see what develops.
.

[wrinklearthur]

Just looking at the photo of your antenna mount that you posted on my antenna thread, (thanks, by the way) - how have you grounded it, given that it's sitting out there behind the spare wheel?

Hi Davo

Can you put up your link to your antenna thread on here, please ?
I wouldn't mind having a read of that.
Personally, I don't have a licence to use vks-737 at the present, but do intend to get the appropriate permission soon, I have had my Amateur radio licence ( vk7kba ) since about 1976.
.

[Davo]

Here it is, from right next door in this section.

http://www.aulro.com/afvb/communications-car-audio-electronics/143735-hf-tapped-whip-back-rangie.html

Like I was saying on this thread, it's really hard to get a simple answer with this radio stuff, as most of it shoots straight off into ham territory. I tried looking for a picture of how a mobile HF antenna radiates, for instance, and wound up with all these highly technical diagrams! Whew!

[patto1]

Thanks Wrinklearthur .... when I get a bit of spare time I will try your suggestion

thanks

[Rusnut]

Quote:
And something else I read the other day said that braided copper is best for grounding body panels And it sounds like ideally you need one of these straps for every door and the bonnet of a vehicle?




better use bi-metal luggs

[Davo]

Yes, I've read the same thing over the years. It sounds like something you can do one panel at a time to try and reduce the noise, though I've read of people just doing this as a matter of course. I'd be inclined to just go ahead and do it so I know at least it's done.