More HF interference afloat!

[MM5AHO]

After reading the account of a RF noisy fridge controller that Conachair has, I was musing on the issue that I have yet to solve from last summer.
Operating an HF radio transmitter for extended periods while anchored in isolated places (like this sumer at Skerryvore Lighthouse), I want a better supply of power than just running the engine at idle. (which works, but aint great news for the engine - glazing possibility, and its a bit noisy being so close to the radio), I took on one trip a generator. One of these suitcase types, and one with an inverter. The advantage of the inverter is that when demand is lower the generator throttles back, but voltage does not sag, nor does frequency. The disadvantage is that the inverter puts out a tremendous amount of RF noise, enough to make the radio unuseable.
Since bringing that gennie ashore, I've tried a few things to quieten it.
Firstly I took the control board and inverter out and cleaned up the poor earthing joints. It had painted over connections etc. That was a good idea, but made no difference.
Next I fitted a small suppressor / filter to the live and neutral wires, close to the output of the inverter, and on that side of the outlet socket.
That reduced noise level on the radio's S meter from about S9+20dB to S9.
An improvement, but not enough.
So I took that fairly simple filter out and fitted a mutipole one. The first had about 3 capacitors and one inductor. This one has three inductors and about 9 capacitors. Now I'm done to S7. All heading in the right direction, but not enough.
I've tried disconnecting the earth line. (I'm running a 240V - 12VDC inverter style transformer to get to 12V DC for the transceiver.). The transformer is not an issue at all, I've used this one for many applications from mains, generators etc and no RF noise at all.

For reference: (in case it might better inform your suggestions?)
Transceiver: Yaesu FT857. Antenna: insulated backstay. ATU Yaesu FC30 located about 1m under the backstay in the hull, and connected to ant by 1m of thick cable, stood off conductors such as pushpit. Coax to ATU, Mini8 about 5m run. DC supply to transceiver, thick dedicated cables from the main battery switching point where there are very thick supply cables from battery. Earthing from ATU: 5 counterpoises the length of the hull spread over the width, one centre, two each side, trailing from stern (ATU connected) to bow. This system works very well other than off the generator.

I have the radio and generator set up in the workshop with a small antenna simulating the boat setup in order to try to find solutions to this issue.

What do the experts say?

 

[VicMallows]

You have clearly identified the source of interference as the generator-inverter.

It's a very long time since I was active on the HF bands, but I'm surprised you would even consider having a high-frequency switching device operating anywhere remotely in the vicinity if you are trying to work DX. ( Indeed I would think you would seek out an isolated anchorage specifically to avoid electrical noise?).

It can't be that pleasant operating on a Rival 32 with a suitcase generator running anyway?. How much power are you running on the transceiver.....I would have thought you could sustain sufficient time on batteries while operating, and then charge them up as necessary from the petrol genny or whatever.

G3TSM

 

[ytd]

The generator will pass normal EMR emissions standards but your HF reciever is one of the most sensitive EMR detectors made. You could try putting the generator in a faraday cage with filters on the charghing leads to stop them radiating but getting a bigger battery is probably the easiest.

 

[William_H]

HF noise

The "inverter type 250 to 12v transformer" makes me wonder if it is a switch mode type power supply and if this is making noise. (switching at 100s of Khertz.) If it is then an old fashioned iron tranformer might be quieter.
However you seem to have isolated the noise to the generator. Gasoline engines of course generate noise from the ignition system. You might be able to source and fit in an aircraft type fully shielded spark plug and fit shielded ignition wires.This may help. However I would expect you would identify this noise as varying with engine speed.

So down to the inverter. I saw an article a long time back and can't find it again about building 50 hertz resonant filter. Massive inductors and capacitors so perhaps not practical. So I presume your filter is just to clean up the high frequency noise which is on a still essentially square wave AC supply. (unless it has a true sine wave inverter) (not likely).
A suggested you might need to build a shielded enclosure for the generator using feed through capacitors and inductors making a filter. This may reduce the noise.
Or as said fit another battery Fit also a smart charging type regulator or higher voltage regulator to charge the batteries off the engine at more than idle power. Might need a bigger alternator.
good luck olewill

 

[MM5AHO]

Bit more info I forgot to add initially.
The Switch mode PSU is dead quiet RFwise, I've proven that at home. Its a type designed for this type of service, and despite having switching at hundreds of kHz as suggested, does not emit RF detectably.

But the genny! Running the genny on the deck it has a low audible noise level, so quite comfortable with that. (as opposed to having to wear earphones in the cabin to hear over the engine noise.

I run 100W when running the engine, and 20W off the battery. We have two batteries, both connected when engine running, isolating one when engine off, (and alternating which is on duty each switching). So in effect running a radio off a single 70Ah battery - 100W would not take long to suffer volt sag.

The genny makes a noise when connected to the PSU (which takes 240Vac to 12Vdc), which is then connected to the radio.
If I run the radio off the boat bettery, but run the genny and PSU, (but no load), then there's little noise.
I conclude from this that the rf is being conducted through the cables, hence my attempt to filter this.
There's still one connection unfiltered, thats the earth lead in the mains cable from genny to psu. I now wonder if thats the conductor and intend trying to disconnect earth and see what happens. (I'm now doing this in the workshop as the boat's on the land for the winter).

I have seen a variable speed inverter style genny used for this application without issues, it all seems to be about the design of the inverter - shielding and filtering.

 

[Nick_Pam]

For reference: (in case it might better inform your suggestions?)
Transceiver: Yaesu FT857. Antenna: insulated backstay. ATU Yaesu FC30 located about 1m under the backstay in the hull, and connected to ant by 1m of thick cable, stood off conductors such as pushpit. Coax to ATU, Mini8 about 5m run. DC supply to transceiver, thick dedicated cables from the main battery switching point where there are very thick supply cables from battery. Earthing from ATU: 5 counterpoises the length of the hull spread over the width, one centre, two each side, trailing from stern (ATU connected) to bow. This system works very well other than off the generator.

I have the radio and generator set up in the workshop with a small antenna simulating the boat setup in order to try to find solutions to this issue.

What do the experts say?

I run an FT857 in my car which has an 85Ah battery and running 100w pep on HF SSB I can operate quite happily whilst parked up for over 3 hours and still have enough juice in the battery to start a V8 diesel.

An 857 operating on SSB will draw an average of 8-9 amps, so your 70Ah battery will power it quite happily for about 4 hours and still be around 50% charged.....remember 100w pep is only about 40w average "talk" power.....

I'd be more inclined to run the rig from the battery and then charge it via the onboard engine, or if you prefer a 12v car-type battery charger from the genny, when you are not operating......less ambient noise when listening for DX too!!

Just a thought........Nick (G7EQM)