MHC-9000 RFI

[KD5XB]

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...

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]

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.

OK, I checked further and got more info. In Europe and Japan trucks and buses have 24 V systems, and also the US military, which universally uses 24 V systems for all vehicles. As you say though, even the largest trucks on the road in the US have 12 V systems.

24 V is preferred where it is used because it gives more power and is lighter in weight.

 

[Mr Happy]

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.

You are being advised that the inverter might cause the C9000 to emit more RFI than it would emit if driven from a pure sine wave or from 12 V DC. You believe otherwise. You may of course be right, but you are asking for suggestions and that is a very cheap suggestion to try. If it doesn't help any, what have you lost?

 

[VidPro]

use a choke?

i would have to do some tests myself.
and here is how i would test:
put the charger in connected with a seperate external AC cord at the lot or at home (assuming you can get it there), and see if you have noise being generated right out of the charger. for various reasons.

put about a 50watt Incan light bulb on the AC converter, and see how much noise it gives when doing its conversion. the quantity of noise (often) is relative to the quantity of current being drawn on the device. unlike switching electronics the bulb would be flat resistive, and provide for a control.

Bring a seperate battery that is not tied to the system, and run the inverter off this seperate battery for testing.

That give me many clues:
Is the RF being transmitted/aided through the cab wiring
is the AC converter really noisey when doing real work.
does the charger itself mess with the radio frequencies your on, when getting normal sine wave.
is the converter and its often very poor simulation of a sine wave assisting the chargers pulsing and switching in creating more harmonics and noise.
Is the converter reaching full voltage, as many converters dont output a full sine, they also dont output the full voltages, how bright is the light compared to being plugged in normally.

 

[Russel]

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.

Sorry, I should be clearer.

There is a possibility that the AC adapter that came with the MH-C9000 (a switching power supply) is causing some of the RFI. This is above and separate from your inverter. If you eliminate both the inverter and the MH-C9000 AC adapter you may be eliminating most of the RFI. I guess that the question is how much of the RFI is coming from the C9000 charger alone.

I have 2, 17, and 20 meter SSB and CW transceivers (I'm an Amateur Extra), so I can try some experiments here. I am curious how much RFI the charger produces as well as how much the AC adapter creates. I haven't experienced any RFI interference from any charger that I use, but I don't have my antennas in close proximity like you probably do in your truck.

[Edit]
Looks like you run APRS from your truck. It's been a long time since I've done packet radio. I might have to dust off my old Kantronics 9612 and see what's on the air here in southern California.
[End edit]

 

[KD5XB]

Yeah -- everything is close in the truck. You can't hardly smile without bumping your cheeks on the walls!

I went and bought a lighter plug cord today and I'll give it a try this next trip. I'm headed out tomorrow, so have ample opportunity to find out what it does.

Also have to figure out where to mount the Bugcatcher on the truck -- that problem is going to be HARD since the mirrors are full already!

 

[Russel]

I can see, with all the equipment you run in your truck, that the inverter you run is for much more than just the battery charger. At lease you have that problem controlled with DSP.

I had a Yaesu FT-757GXII in my pickup truck for a while years back; RFI can be a pain in the rear.

 

[jayflash]

If the charger will operate on 12v why use two more pieces of electronic equipment?

If RFI is still generated by the charger itself, placing it in a metal box may not work unless it's grounded ... and that still may not work if RFI is "back fed" through the cord. Pi filters are available for that problem however.

Good luck, I hope you find a solution soon.

 

[cckw]

As jayflash said you may need to ground the can. If in the can only you are counting on the can to block the RF and have it fade to death inside the can. by adding a ground to the can you are grabbing the RF and sending it somewhere. I'm going to bet you will need the ground.

I'm also going to advise staying with the ammo can plan and not doing the foil lined box. even grounded, I think the foil will pass too much, it is very thin.

 

[KD5XB]

Still there on 12VDC power direct from the truck.

 

[Russel]

Well I guess that answers that question. Apparently the switching circuit is making the RF noise. If you know anyone with a LaCrosse BC-900 charger you might try it as a possible alternative. I think Apollo Cree is correct in that the BC-900 uses linear regulators rather than switching regulators like the C-9000. That may make the difference.

 

[n3eg]

You do have the radio chassis grounded with the shortest possible path, right? I found that makes a difference in the amount of noise that leaks into the radio. Any little bit helps on 75 meters.

By the way, not to revive a worn out debate, but many trucks I've seen are 24 volt start and 12 volt run. Good thing we don't have 100 watt UHF radios in service any more and can use the circuit breaker panel now...no more cranking the starter to find which battery stays grounded for a direct connection.

 

[TakeTheActive]

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...

+1 :twothumbs

I've been following this thread since it's inception.

1. 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...
   
   ...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...
   
   ...Anybody else got a suggestion to cure this RFI?

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

3. 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...

4. ...If RFI is still generated by the charger itself, placing it in a metal box may not work unless it's grounded ... and that still may not work if RFI is "back fed" through the cord. Pi filters are available for that problem however...

5. Still there on 12VDC power direct from the truck.

[WAG - "Thinking-out-loud " mode]

Did you try the ammo can yet?

I have a RadioShack 15-2117 "Multi-Device / Learnable / etc..." Remote that's backlit and when I enable the back light, I can hear a whine (thus, a high-frequency oscillator has been engaged). The C9000 also has an "Always ON" backlight.

1. If you haven't tried the 'Grounded' ammo can idea yet, please do and let us know if it works.
   .
2. If it *DOES* work, maybe (If solving this 'problem' is *REALLY* important to you ) consider locating the power lead(s) to the backlit display and inserting an ON/OFF switch. :thinking:

[/WAG - "Thinking-out-loud " mode]

Good Luck!

 

[KD5XB]

Did you try the ammo can yet?

I have a RadioShack 15-2117 "Multi-Device / Learnable / etc..." Remote that's backlit and when I enable the back light, I can hear a whine (thus, a high-frequency oscillator has been engaged). The C9000 also has an "Always ON" backlight.

No, haven't tried the ammo can yet -- might do that NEXT weekend.

I guess I'm fortunate -- spent many years on military flight lines so I don't hear those oscillators any more! Don't hear TV flyback transformers, either, but not sure they still exist! LOL!

Did you see the new rules going into effect for clearances to cross runways?

 

[TakeTheActive]

...Did you see the new rules going into effect for clearances to cross runways?

I "Did My Homework" and got my ASEL license in 3 months (just after I turned 40). I then followed that up, bought into 50% of a 1969 PA28-140 w/IFR, and got my IFR rating within the next year. After a few years of "BLISS" (i.e. 9-5, then go flying! :nana: ), I decided to become "Self-Employed", earn *MUCH* more money and give up *MOST* of my free time.

Thus, for the past ~10+ years, my airplane just sits (and recently, my partner wants to sell it! )

So, no - I haven't kept current and am not aware of the "new rules going into effect for clearances to cross runways" (but *WISH* I was... :sigh: )

...No, haven't tried the ammo can yet -- might do that NEXT weekend...