inverter RFI hash in ham radio

[K4ZZR]

I have Fleetwood Bounder 33C motor home with a 4000 watt inverter. When it's in use, it creates a lot of RFI hash in my HF radio (I'm a ham radio operator). The cables going in and out of the inverter are too big to put any ferrite beads on them. Just wondering if anyone has found a solution that might help reduce the noise (other than not using the inverter)?

Thanks,
David, K4ZZR

 

[Lou Schneider]

When I was installing broadcast transmitters, the manufacturer provided ferrite toroid rings for all wires and cables entering or leaving the transmitter cabinet, including the AC power leads and the 3 1/2 inch coaxial transmission line.  So large ferrite cores do exist.

You could try passing both of the power leads through something like this, as close to the inverter as you can get it.  Pass both leads through the ferrite so the DC magnetic fields cancel each other out.  The magnetic field around a single high current DC line can saturate and overheat the ferrite.

https://www.jpmsupply.com/Toroid-Core-FT240-43-Ferrite-p/38021.htm?click=2

Twisting the power leads together will also help cancel out common mode AC noise.

 

[DonTom]

I have Fleetwood Bounder 33C motor home with a 4000 watt inverter. When it's in use, it creates a lot of RFI hash in my HF radio (I'm a ham radio operator). The cables going in and out of the inverter are too big to put any ferrite beads on them. Just wondering if anyone has found a solution that might help reduce the noise (other than not using the inverter)?

Thanks,
David, K4ZZR

I would expect QRN from any inverter. I find the small PURE  sinewaves inverters to be the WORSE of them all. They radiate more HF trash than a MSW inverter. That's been my experience


But why do you need an inverter? Won't all your ham stuff run on your house battery?


I turn all my inverters off when I am on the air.  Converters are fine, but not inverters.


73, -Don-  AA6GA  Auburn, CA

 

[Arch Hoagland]

When I was installing broadcast transmitters, the manufacturer provided ferrite toroid rings for all wires and cables entering or leaving the transmitter cabinet, including the AC power leads and the 3 1/2 inch coaxial transmission line.  So large ferrite cores do exist.

You could try passing both of the power leads through something like this, as close to the inverter as you can get it.  Pass both leads through the ferrite so the DC magnetic fields cancel each other out.  The magnetic field around a single high current DC line can saturate and overheat the ferrite.

https://www.jpmsupply.com/Toroid-Core-FT240-43-Ferrite-p/38021.htm?click=2



Twisting the power leads together will also help cancel out common mode AC noise.

Lou...how many watts were those transmitters and who was the manufacturer?  Just curious...repaired 50KW and 100 KW transmitters in the Navy for four years.  Low Frequency and Medium Frequency.

 

[K4ZZR]

I would expect QRN from any inverter. I find the small PURE  sinewaves inverters to be the WORSE of them all. They radiate more HF trash than a MSW inverter. That's been my experience

But why do you need an inverter? Won't all your ham stuff run on your house battery?

I turn all my inverters off when I am on the air.  Converters are fine, but not inverters.

73, -Don-  AA6GA  Auburn, CA

The inverter is built-in to my Class A motorhome and when boondocking provides 120 volts AC to appliances when using the 12 volt DC house batteries.  Turn off the inverter and I will lose power to my fridge, TV, coffee maker, microwave, and 30 amp PS.  I could run cable straight to the house batteries, but I'm not going to.  I use a 30 amp power supply for my station. 

73,
David, K4ZZR

 

[K4ZZR]

When I was installing broadcast transmitters, the manufacturer provided ferrite toroid rings for all wires and cables entering or leaving the transmitter cabinet, including the AC power leads and the 3 1/2 inch coaxial transmission line.  So large ferrite cores do exist.

You could try passing both of the power leads through something like this, as close to the inverter as you can get it.  Pass both leads through the ferrite so the DC magnetic fields cancel each other out.  The magnetic field around a single high current DC line can saturate and overheat the ferrite.

https://www.jpmsupply.com/Toroid-Core-FT240-43-Ferrite-p/38021.htm?click=2

Twisting the power leads together will also help cancel out common mode AC noise.

Good info....thanks!

73,
David, K4ZZR

 

[DonTom]

The inverter is built-in to my Class A motorhome and provides 120 volts AC to appliances when using the 12 volt DC house batteries, when boondocking.  Turn off the inverter and I will lose power to my fridge, TV, coffee maker, microwave, etc. 

73,
David, K4ZZR

Has me curious.  Your fridge can only run on 120 VAC?  The other stuff shouldn't be an issue unless there is other people who want to use it while you're on the air. 


I RV alone these days since I have been widowed for few years. And my fridge runs on propane when I am boondocked. So being on the air is no such issue for me.


Anyway, you may find no matter what you do, you still will get QRN from the inverter. Most likely direct from from it. So the ferrite cores may help a little, but it probably will not get it down to a reasonable level. Like most such QRN issues, it's more often solved by experimentation, when it can be solved.


BTW, I operate CW only, from my RV I run a KX2 to a KXPA100 to a TW4040 (or 8080, etc) which is a vertical dipole that I set up outside the RV when boondocked.  The antenna is only 8 feet long (even on 80M).


I filled up several pages of my logbook at 200 feet below sea level, boondocked at Furnace Creek in Death Valley a couple of months ago.


Here, in Auburn, I run a Yaesu  FTdx1200 to a low G5RV about 20' feet up in the trees.


73, -Don-  AA6GA Auburn, CA

 

[Lou Schneider]

Lou...how many watts were those transmitters and who was the manufacturer?  Just curious...repaired 50KW and 100 KW transmitters in the Navy for four years.  Low Frequency and Medium Frequency.

The manufacturer is Nautel out of Peggy's Cove, NS.  They've pretty much cornered the market by making bulletproof solid state AM and FM broadcast transmitters.  The company started out making the first solid state high power navigational beacon transmitters some 50 years ago.  On my last job it was mostly 3 - 10 Kw FM transmitters, prior to that I worked with and installed up to 50 Kw transmitters, both AM and FM over a 40+ year career.

 

[DonTom]

  I could run cable straight to the house batteries, but I'm not going to.

That's what I did. A big advantage of having a junky 21 year old RV. I don't mind drilling holes in it!


I kinda overdid it, as my cable could handle a lot more than my battery can. I have  large 350 amp Anderson connectors on the end. I plug in  whatever I want into a large mating cable.  My small 114AH battery is the weak link, which will be changed to a couple of 100 AH lithiums  before my next RV trip.


73, -Don- AA6GA  Auburn, CA

 

[John From Detroit]

Is that inverter MSW or True Sine Wave

I have used two True Sine wave and my TS-2000 could not tell if they were operating, Standby OR off

Both were Xantrex. one a Prosine 2.0 (no longer made) the other Freedom 2000 XC (low priced) still working

 

[Larry N.]

Has me curious.  Your fridge can only run on 120 VAC?

Probably a residential fridge -- they're more and more common these days.

 

[Mark_K5LXP]

There's conducted and radiated RFI.  So one is being carried by the wiring going in and out of the inverter, the other is being "sprayed" out of the box.  If it's radiated RFI all the ferrites in the world placed on the cables won't help, so the first step would be to isolate the source.

From there it comes down to isolation - isolating and bypassing wiring and possibly enclosure shielding.  Any of these can be a bit of work so you have to really want to do it.  Another aspect of RFI is susceptibility.  The inverter may be generating some level of RFI but is it only at objectionable levels because the affected receiver has it's antenna effectively too close?  Many portable and temporary antennas suffer from common mode so while the antenna maybe outside the RV, the feedline is also picking up whatever is nearby and if it's running near the inverter or a circuit it's supplying, whatever's there gets readily picked up.  Improvement could be as simple as adding a feedline choke or just rerouting it.

The first step in any EMI/RFI mitigation is to characterize the problem.  Note the band/frequencies of trouble and respective interference strength.  Then make a change, whatever it is, and re-do the sweep.  The interference may be better, worse or the same and that is a clue whether whatever you've done is associated with the source.  Iterative steps like this will zero in on the most effective place and way to mitigate the problem.  You may not get 100% depending on the degree of fix implemented but often you can get it at least "acceptable".

Mark B.
Albuquerque, NM

 

[DonTom]

Is that inverter MSW or True Sine Wave

I have used two True Sine wave and my TS-2000 could not tell if they were operating, Standby OR off

Both were Xantrex. one a Prosine 2.0 (no longer made) the other Freedom 2000 XC (low priced) still working

You could not tell it was on at  any HF frequency? I have several inverters, small ones up to a large 5KW, both MSW and PSW. They all make noise on 7 MHZ, the PSWs the worse. But my PSWs are all small cheap ones that I only use to charge computer batteries and such.  i assume the more expensive larger  commercial ones will not be so bad.


-Don-  Auburn, CA

 

[John From Detroit]

You could not tell it was on at  any HF frequency? I have several inverters, small ones up to a large 5KW, both MSW and PSW. They all make noise on 7 MHZ, the PSWs the worse. But my PSWs are all small cheap ones that I only use to charge computer batteries and such.  i assume the more expensive larger  commercial ones will not be so bad.


-Don-  Auburn, CA

On any and every frequency I work Including 7.72 Both of them were dead silent.  Now I've heard cheaper MSW inverters (Sounds like someone welding on your antenna)  but both of mine and I tested them in every mode. Dead silent.

I just got done running a 50 foot LONG wire here in the apartment.  TS-2000 feeds KAT-1 tuner feeds the wire (About 52 feet total The wire is actually two 50 foot 16ga speaker wires embedded in tape (Ghost Wire) the  Same and I mean the Exact same color as they painted my walls.  Tape disappears where it is smooth.  KAT (Tuner) tunes it now that I got it reconnected properly.  No contacts yet but After getting it up and clattering I took a nap.(The relays clatter when I hit Tune There are 22 Relays that's 2^22 possible tuner settings and 22 LED's as well along with 23 switches in case you want to manually tune it)

 

[DonTom]

On any and every frequency I work Including 7.72 Both of them were dead silent. 

What make and model are those inverters?  And BTW, what is on 7.72 Mhz ( as that is well above the 40M ham band)?


-Don- Auburn, CA  AA6GA

 

[HappyWanderer]

I made a 10 gauge power cord for my radios, with alligator clips on one end and power poles on the other.

It fits through the slide gasket and connects to the house batteries below. My go box has a 30 amp power supply, but I can simply unplug the power poles and go directly to the batteries when desired.

 

[John From Detroit]

What make and models are my hash free inverters.

Xantrex. original was prosine 2.0 (2,000 watts true sine)
Replacement Freedom 2000 XC (Same power ratings)
30 amp AC in with pass through and the ability to charge batteries off shore/generator power

 

[DonTom]

Xantrex. original was prosine 2.0 (2,000 watts true sine)
Replacement Freedom 2000 XC (Same power ratings)
30 amp AC in with pass through and the ability to charge batteries off shore/generator power

I will remember that if I ever have the need to run an inverter while on the air. But I think that is very unlikely. It's really no issue to me as all make sure all my ham stuff runs on 12 VDC.

73, -Don- AA6GA Auburn, CA

 

[John From Detroit]

Here I needed a pair of like 25/30 amp power supplies. Well the Freedom XC-2000 puts out up to 80 amps at battery voltages SO.. that and a few batteries in a plastic container to protect the property and job done