RF noise from Generator

[MM5AHO]

I have a Kiam 20001 invertor style generator.
When I use it on board and also use the HF radio, the genny puts out so much RF that the radio is unusable. The radio is 12VDC powered, so the generator has a 12V PSU attached to change 240V AC to 12V DC.
I've tried putting a filter in the 240V output inside the gereator case, and this helped, but didn't solve the problem.

Any suggestions?

 

[Mirror Painter]

Don't use H.F. when the generator is on.

Actually I'm not trying to annoy you, honest. But surely this isn't your only source of 12V on board? Or am I missing something?

 

[Bru]

OK, the first question is whether we're actually talking about RF interference or whether the problem is noise on the 12v supply to the HF radio

Step 1 ...

Do you have access to shore power?

If so, what happens if you run the mains supply to the radio off shore power (if it's fine that probably eliminates the mains adaptor as the source of the problem)

Can you run the HF off 12v battery power whilst running the genset with the mains supply isolated from the radio?

If you can do that, what's the result?

 

[lw395]

The 240V to 12V unit may also be the culprit.
Some capacitors across its output may help, along with an inductor or choke in series.

To do this job properly, you need to understand the grounding of the radio, aerial and power supplies.
You want to avoid ground loops.
It may be best to separate RF ground from 12V power ground.

It might be worth running the radio from an isolated 12V battery while the generator is running, that could show whether the interference is on the power connections or radiated.

It's not a trivial problem sometimes.

 

[wotayottie]

If it is newish and it is RF interference then it is Kiam's problem - that level of RF is illegal. It doesnt comply with standards.

 

[MM5AHO]

A few more explanations. (Thanks for suggestions so far).

I can run the HF off the 12V batteries, but running 100W RF for extended periods off batteries doesn't work, they're too small for that.

The genset produces RF that is conducted along the mains lead plugged into it, and also radiated from that lead. (even when the lead has nothing on the other end).
Have tried several 240-12V PSUs - no difference. The PSU when running from shore mains produces no RF. Its only when the genset is the source of the 240V

Have tried putting the generator as far as possible (bow) away, and that helps (S9+60 reduces to S9+20)

The HF set and setup seems fine otherwise. I can run off the batteries with the engine ticking over for as long as I like, and no RF from these. I do get a little noise from the GPS, but that's easily switched off.
The engine is a diesel.
I can run 20W RF off the batteries alone. 100W tends to sag the voltage a little unless the engine is running.

When running the transceiver off the batteries, and without the 240-12V PSU connected to those batteries or to the HF, (ie just genset running powering the PSU), there's still a lot of noise. (the radiated part).

I have fitted a commerical mains RF filter into the generator, right at the output of the invertor, between it and the mains outlest point on the casing, and this has helped. Now with this setup the noise is about S9, still both radiated and conducted.

 

[Bru]

Conclusion seems pretty straightforward

As Wotayottie has already intimated, it sounds very much as if the genset is either faulty or badly designed, it should not be generating significant RF interference in the way you have described

One possible cause of the excess RF might, and I emphasis the might, be earthing issues. We have had problems sometimes at festivals with gensets producing noisy mains due to poor or non-existent earthing

 

[lw395]

Conclusion seems pretty straightforward

As Wotayottie has already intimated, it sounds very much as if the genset is either faulty or badly designed, it should not be generating significant RF interference in the way you have described

One possible cause of the excess RF might, and I emphasis the might, be earthing issues. We have had problems sometimes at festivals with gensets producing noisy mains due to poor or non-existent earthing

Don't quite agree with that.
The allowed levels are significant, particularly in the context of an HF receiver, which will have a sensitivity in microvolts.
It is often generally regarded as bad practice to use switch mode power supplies, like an inverter generator, with radio equipment. The radiated emissions will depend on the wiring, so cannot be solely blamed on the generator.
The conducted interference can be addressed from the point of view of emissions or susceptibility. A radio set intended for vehicle or boat use ought to have fairly good immunity.

I agree that earthing is very possibly the cause/carrier of the problem. I'm reluctant to speculate on this, because I would not want people to interfere with safety earths on the basis of my casually written explanation, and I don't have enough info to go on.
Perhaps re-reading the manual for the radio/ATU and 240-12V supply might help?

 

[Bru]

RF isn't really my area of expertise so I've little experience to fall back on to judge whether a piece of equipment operating withinspec would normally cause interference on an HF set.

I wouldn't expect a generator to be churning out so much RF noise as to be radiating significantly at high frequencies as the op describes though but on the other hand I'm not familiar with just how sensitive an HF receiver would be

I do agree vis earths though, not to be messed with. Especially never to solve problems by disconnecting the earthing (an all too frequent hazard encountered in the audio world)