MHC-9000 RFI

I've had an MHC-9000 charger for quite a while now. I use it in the 18-wheeler to charge batteries for my GPS. It works very well.

HOWEVER -- it generates Radio Frequency Interference something fierce when charging! It is so bad that 2-meter SSB & CW and 17- and 20-meter SSB are all but unusable. At various times I have wound the power cord on ferrite cores but that didn't help any at all.

Anybody else got a suggestion to cure this RFI?

Thanks,
Earl

just put the charger into a metal case while charging, given that it is big enough to dissipate heat

I've had the same problem with car cellphone chargers, and the catch is that the RFI was coming from the phone end and not the switching supply end. Toroids won't help at all with that.

You might have to confirm which end it is and start bypassing and shielding.

By the way, despite all the other reported problems, my BC-900 generates no RFI...

As a test, certainly not for long-term use, find a cardboard box big enough to hold the charger. Line the box with aluminum foil (outside is safer), put in a hole for the plug and put the charger inside. Be extremely careful not to allow any shorting...

If your RF is gone, go find that metal box, and punch a whole lot of small holes in the top and sides. A home brew faraday shield.

Oh gee, I never considered trying to shield the whole thing! I have an ammo can handy, I'll try drilling a hole in the side for the power wire to fit through, and put the charger inside the ammo can -- maybe that'll fix it.

OTOH, the wall wart for the MHC-9000 is a switching power supply. I'm guessing there's a fair chance that the RFI is from there -- but I'll try putting the charger inside the ammo can first.

KD5XB said:

OTOH, the wall wart for the MHC-9000 is a switching power supply. I'm guessing there's a fair chance that the RFI is from there -- but I'll try putting the charger inside the ammo can first.

Click to expand...

But you said 18-wheeler above. If you're using the wall wart you must be getting 120 V from somewhere, and the inverter for that could be generating RFI as well?

I'm guessing the truck has 24 V electrics, otherwise you could power the C9000 directly from the battery and see if that helps. Do trucks have 12 V lighter sockets?

Yep, I use an inverter -- and it has it's OWN RFI, but the MH-C9000 is so much worse that I'd like to find a fix for that first. The inverter can usually be taken out with the DSP but the battery charger cannot.

Do you have a 24V. pure sine wave inverter?

An example:
http://www.altersystems.com/catalog/samlex-pure-sine-wave-150-watt-inverter-24v-p-1781.html

Less expensive modified sine wave inverters are known to cause RFI in some devices. It might be the root cause of your problem.

I really don't know what I am talking about here, but semis in the US at least don't have 24V systems, do they?

And yes, modified sine wave inverters and battery chargers are notorious for not getting along, but a true sine wave system is price-eee.

VegasF6 said:

I really don't know what I am talking about here, but semis in the US at least don't have 24V systems, do they?

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I don't know, but they often do in Europe so I presume the US might be similar?

VegasF6 said:

I really don't know what I am talking about here, but semis in the US at least don't have 24V systems, do they?

Click to expand...

Actually I don't think it's at all uncommon for them to have 110/220, and I believe the reefer units even have 440.

Dave

ronkar said:

Do you have a 24V. pure sine wave inverter?

Click to expand...

No, I don't. I have a 12VDC->110VAC inverter. Modified sine wave.

As I said earlier, the inverter has its own RFI, but the DSP can usually hide it, and the MH-C9000 is MUCH worse and can't be hidden by anything I have in the transceiver.

Mr Happy said:

I don't know, but they often do in Europe so I presume the US might be similar?

Click to expand...

No, in the United States, every semi that I have ever heard of uses a 12VDC system. Usually they have 110VAC only if the driver purchases an inverter for himself.

KD5XB said:

No, in the United States, every semi that I have ever heard of uses a 12VDC system. Usually they have 110VAC only if the driver purchases an inverter for himself.

Click to expand...

Ah, well that's good then. My earlier suggestion stands: why not plug the 12 V directly into the C9000 using a 12 V power cord and avoid the inverter and wall wart altogether -- see if that reduces the RFI?

KD5XB said:

No, in the United States, every semi that I have ever heard of uses a 12VDC system. Usually they have 110VAC only if the driver purchases an inverter for himself.

Click to expand...

I just did a quick check with Google and evidently large trucks and buses in the US do often have 24 V batteries and electrical systems just like other parts of the world. It's because the larger engines need a stronger starter motor to turn them over, and the other electrical systems have larger power requirements too.

However, they will still have a 12 V lighter socket in the cab as that is standard for such sockets.

Mr Happy said:

Ah, well that's good then. My earlier suggestion stands: why not plug the 12 V directly into the C9000 using a 12 V power cord and avoid the inverter and wall wart altogether -- see if that reduces the RFI?

Click to expand...

As I said earlier, the inverter has its own RFI, but the DSP can usually hide it, and the MH-C9000 is MUCH worse and can't be hidden by anything I have in the transceiver.

Mr Happy said:

I just did a quick check with Google and evidently large trucks and buses in the US do often have 24 V batteries and electrical systems just like other parts of the world. It's because the larger engines need a stronger starter motor to turn them over, and the other electrical systems have larger power requirements too.

However, they will still have a 12 V lighter socket in the cab as that is standard for such sockets.

Click to expand...

I've driven Peterbilt, Freightliner, Kenworth, and International trucks. Never had one with a 24VDC system. What can I say? Google might be full of them, but the road is NOT.

KD5XB said:

...the MH-C9000 is MUCH worse and can't be hidden by anything I have in the transceiver.

Click to expand...

So, you are getting RFI from the MH-C9000 when powering it directly from 12 volts DC?

n3eg said:

By the way, despite all the other reported problems, my BC-900 generates no RFI...

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IIRC, the BC-900 uses linear regulators vs. switching regulators on the C-9000 to control voltage and current to the individual cells. Switchers have a lot of advantages, but RFI is not one of them. There might be some reasonable things that could be done in the design to reduce RFI, though. It might be worth sending some polite feedback to Maha.

Russel said:

So, you are getting RFI from the MH-C9000 when powering it directly from 12 volts DC?

Click to expand...

I promise I'm not going off on a rant, but one of the most aggravating things I find in email and on forums is the fact that people don't read what I write.

No, I do not power the MH-C9000 from a lighter plug, I power it off the inverter, which has its own kind of RFI and is not at all like the pulsing noise you get when the MH-C9000 is charging. The inverter noise is there any time the inverter is powered up, regardless of the load or lack of a load.

ronkar said:

Do you have a 24V. pure sine wave inverter?

Click to expand...

KD5XB said:

No, I don't. I have a 12VDC->110VAC inverter. Modified sine wave.

Click to expand...

ronkar said:

Less expensive modified sine wave inverters are known to cause RFI in some devices. It might be the root cause of your problem.

Click to expand...

Mr Happy said:

My earlier suggestion stands: why not plug the 12 V directly into the C9000 using a 12 V power cord and avoid the inverter and wall wart altogether -- see if that reduces the RFI?

Click to expand...

Russel said:

So, you are getting RFI from the MH-C9000 when powering it directly from 12 volts DC?

Click to expand...

KD5XB said:

No, I do not power the MH-C9000 from a lighter plug, I power it off the inverter...

I promise I'm not going off on a rant, but one of the most aggravating things I find in email and on forums is the fact that people don't read what I write.

Click to expand...

Not wanting to be an asshole here, but you have been given a suggestion and in spite of your own advice you are ignoring what other people have written. Powering directly from a 12 V cord might perhaps reduce the RFI, it might not. But if you don't try it you will never know...