Compatibility problem with VHF amateur radio


I have recently purchased a 2000 Gran move with 30k on the clock and am very pleased but have one strange problem.
I am a radio ham and have fitted a VHF/UHF two way radio , everything is fine on UHF (430 Mhz) but on VHF (145Mhz) after transmitting for a short while it seems to cut the engine which will not restart for a while . The engine "starts" breifly but will not run. If I leave it a few minuits it will start and run ok. I guess the RF is getting into the engine management unit .
The radio has the antenna at the rear of the vehicle and the radio is connected directly across the battery.
Has anyone any knowledge of this problem and can suggest a solution of what filters might be fitted and where Unknw
It seems a shame not to combine my hobby with the car.
I have never had a problem like this in any other vehicle.

That is a very strange fault

That is a very strange fault Les. I can only suggest that to start with you try running the radio equipment on a stand alone battery, if only to eliminate one possibility. If that proves fruitless then buy a handful of ferrite rings and use these on the most likely feeds to and from the engine management system.

I was once GD8ODB, mostly ssb on 2 metres and managed a best to Yugoslavia terrestrial and handheld to Spain via sporadic e. Also worked from GD land ( Isle of Man) to Kent using 100mw then switched to FM and worked the same station..

73 ( for other readers this means good luck in Ham code) -.-

I agree with the ferrite core

I agree with the ferrite core bit, and also another good idea I reckon would be an attempt to RF screen the ECU in a basic fashion with fine copper mesh. If it's like the Sportrak it won't earth direct to the body via the casing, so you could also replace the mounting screws with plastic ones thru rubber washers.

Dave with a Sporty (Who once when trying out his SSB firestick on his new Sporty couldn't understand why there was no joy at all - until he realised the roof was fibreglass.....):-$

Dave with a Sporty

EMC compatibility 2000 Gran Move

Thanks Dave
I guess that a screen might be a good idea plus ferrites.
The problem with fibre glass roofs is an old one !!!!!
I think the only time I came up against it was with a plastic pig (Robin Regal) and the solution was Baco Foil stuck on the inside to act as a ground plane .......ok on a regal but untidy on a new car !

As I said in aprevios reply I am sure this problem must have shown up b4 with taxis or commercial vehicles using the same EMU.


Glass fibre roofs

I once had a Midas GRP car and with a front mounted vertical on the roof used a pair of radials under the roof and above the sunvisors.

Bacofoil? Should have thought

Bacofoil? Should have thought of that years ago instead of stripping yards of coax to run around the roof and body of a mates plastic pig!

Dave with a Sporty

Dave with a Sporty

emc problem

Thanks for the comments.
I will try the ferrites but guess I will have to try the clip one variety to avoid cutting the feeds . I was also considering de-coupling the feeds with caps but the selection of values might be by the impiricle method !
Surely this engine management unit must be used on other vehicles that use VHF equipment elsewhere such as taxis , delivery vehicles etc?
I am just concernened that the rf is getting directly into the active devices in the unit and any form of decoupling might be ineffective.
Perhaps the screening and decoupling together might work.

Thanks both any other comments or has anyone else solved this one?

73 de Les G6APD

Electronics and cars don't mix.

This is why I don't have anything to do with electronics in cars.

Just squirt the smelly stuff in at 3000psi. If you insist, use a solenoid to stop the smelly stuff being injected, but otherwise, LEAVE THE ELECTRONICS AT HOME.


I agree !

Yep guess your right but if anyone is following this thread I had an interesting conversation with Daihatsu Technical support today and it was suggested that the RF was getting into the imobiliser not the emu.
The suggestion was to try to screen it.
I have done this and added a clip on ferrite to the leads entering this ...... this may have solved the problem but have only tried it static will let everyone know when I have given it a test on the road


RF Hardening of Standard Computer Equipment.

Items to give attention to would be:
1 Any lead except the antenna lead should be wound around the densest radio ferrite rods you can get, this is like a sponge to rf.
2 The antenna lead should be of the fully screened layered foil type. ie not the 'open weave' type.
3. The computer ideally all input leads should be ferrited. The whole case should be within a grounded metal case, generally when hardening the denser/heavier then the better. (if plastic use metal tape bond each strip to next one and to earth), with additional wrapped screening to input wires which should be zig zagged on ferrite before being wrapped and enclosed in metal case.
4 The antenna should ideally be sat above the computer (vertically polarised) so that the computer sits in a natural 'nul' zone. Ideally the 'ground plane' metal sheet needs to screen the computer.
5. Step up the power until a setting is found below the saturation point of the computer.
6 Lastly the transmitter should use a seperate auxilliary, battery not only from the isolation point of view also for security as high power transmit will load the battery as a priority over the nice smooth violtage the computer wants, so although provision is made for this under normal loads the transmit load will prob exceed that design critera.
Doing the above should give the computer a fighting chance to cope with any ajacent hight fr field as well as a moderately low yeild airbust NW.
It may be as well to mention that stopping and using would be the best solution. The opperation of any radio equipment while driving is prob dagerous and illegal for mere mortals, only being safe for members of law enforcement or pilots of complex flying machines.