Hi I used to install HF's for a business that sold them, as you have found they generate a huge amount of noise and we spent weeks trying to sort it out and we pretty much gave up with TD5 Landy's and told prospective buyers that the HF would be useless if the engine was running as the injection system created so much noise it overloaded the transceiver.
Good luck with possibly solving the problem, at the time the electronics guru's within the company also spent many hours delving into the source of the noise and eventually decided that it was not worth the effort and expense involved as it affected a relatively small percentage of HF users. The company has long since closed down so cannot help with contact info of those involved.
Be aware also that the mounting of the auto antenna in the middle of the spare tyre like in the picture is also going to cause problems as the wheel and steel belts in the tyre act as a Faraday cage which affects tuning and function. I know that the top of the antenna is above the tyre but for best use the antenna should be above the tyre, my experience is with the earlier HF's and antenna's so it maybe that later versions are not as greatly affected.
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