Supressing VHF Noise from Inverter/Charger

[markpierce]

My first instinct would be to query the manufacturer.

[deblen]

I have seen this problem when antenna coax braid connection is poor.
Check coax connectors. Check that SO239 conn. on new VHF is grounded to radio case. Inspect coax braid for water/corrosion.

Cheers/Len

[deblen]

Also-have seen poor power connections cause noise on TX.Try a radio check call on 1 watt-draws less current.

[MarkSF]

Am I the only one who thinks its not ideal to have the VHF on the lighting breaker?

[transmitterdan]

Originally Posted by MarkSF

Am I the only one who thinks its not ideal to have the VHF on the lighting breaker?

No, I agree with you. A VHF should ideally be powered directly from the battery or as close as possible. It should have its own dedicated power wires shared with no other devices. Inverter should also have dedicated wires to the battery especially the negative wire. Always use the proper size and type of fuse or circuit breaker.

[a64pilot]

Originally Posted by MarkSF

Am I the only one who thinks its not ideal to have the VHF on the lighting breaker?

No your not, and I was even wondering if there might be a florescent light or something on that circuit too, possibly. I hate "sneak" circuits, everything essential ought to have a home run circuit

But he has already said another radio on another circuit isn't showing similar issues, so as easy as it is to rig a temporary power supply, I'd do that, and if the problem goes away, it's likely coming in on the power supply and easily remedied. Needs fixing anyway, a VHF ought not be on a sneak circuit.

[CaptTom]

Originally Posted by a64pilot

...another radio on another circuit isn't showing similar issues, so as easy as it is to rig a temporary power supply, I'd do that, and if the problem goes away, it's likely coming in on the power supply and easily remedied. Needs fixing anyway, a VHF ought not be on a sneak circuit.

That sums up my current thinking exactly.

Every electronic device manufacturer recommends you locate their device as close as possible to the battery, and run the power cables directly to it. Not very practical, IMHO.

Again, the other radio, wired from the same breaker panel, works fine. Neither that other radio, nor the (rather long) power cable to it is near the inverter. The problem goes away when the inverter is off. There is no measurable voltage drop at the radio during transmission. Transmitting on high or low power makes no noticeable difference.

I'm prepared to question the quality of antenna connection and cable, but the symptoms just don't seem to fit. Plus, moving the antenna cable would mean moving the radio to another location altogether, which I'm sure would solve the problem, but the point is to see if I can get it working where it is, first.

Thanks to all for offering their input!

[smac999]

often I find charger noise on devices to be caused by bad batteries.

[SoonerSailor]

Aged batteries could contribute I think. As they get older, their internal resistance increases. This has a negative effect on their ability to dampen spikes.

The unaffected VHF may have better internal voltage regulation and filtering. Is it a different brand?


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[hellosailor]

Radio Shack or a car audio shop may be able to sell you an "alternator noise filter" kit, which consists of one or a couple of capacitors and coils that are designed to filter out line noise from an alternator. Not the same as 60Hz. noise but it might be effective enough to still reduce that. Shouldn't be expensive, maybe $20.

[rwidman]

Originally Posted by CaptTom

That sums up my current thinking exactly.

Every electronic device manufacturer recommends you locate their device as close as possible to the battery, and run the power cables directly to it. Not very practical, IMHO.

Again, the other radio, wired from the same breaker panel, works fine. Neither that other radio, nor the (rather long) power cable to it is near the inverter. The problem goes away when the inverter is off. There is no measurable voltage drop at the radio during transmission. Transmitting on high or low power makes no noticeable difference.

I'm prepared to question the quality of antenna connection and cable, but the symptoms just don't seem to fit. Plus, moving the antenna cable would mean moving the radio to another location altogether, which I'm sure would solve the problem, but the point is to see if I can get it working where it is, first.

Thanks to all for offering their input!

I do not think the problem is with the antenna because you are having the noise when you are transmitting, not receiving. The actual power that the inverter could possibly induce into the antenna or wire is miniscule compared to the 25 watts your radio is putting out.

A good, cheap tool for tracking rf interference is a simple, old time AM transistor radio tuned between stations. But it's not rf, it's 60 Hz, you say? Modified sine wave inverters put out a lot of harmonics.

If I were you I would start by wiring the radio properly. That is, on it's own circuit from the breaker panel. And it's own negative as well to the buss bar.

Use the transistor radio to find where the interference is coming from - the inverter case, the AC leads or the DC leads. See if it shows up on the DC leads to the radio.

Connect a high resistive load to the inverter (a coffee pot) and see if this changes things. The coffee pot would tent to short out any noise on the AC leads.

Best of luck, report back what you find.

[CaptTom]

The ferrite choke actually seemed to make a big improvement. It just so happened that the charger was putting out a fairly high amperage at that moment though, so I think that may be another factor. I tried again later, when it was back to float charge, and some of the hum had returned. It was nowhere near as bad; quite usable actually. But I still plan to run a dedicated power cable.

[rwidman]

Originally Posted by CaptTom

The ferrite choke actually seemed to make a big improvement. It just so happened that the charger was putting out a fairly high amperage at that moment though, so I think that may be another factor. I tried again later, when it was back to float charge, and some of the hum had returned. It was nowhere near as bad; quite usable actually. But I still plan to run a dedicated power cable.

Knowing now that the noise was when the inverter/charger was in the charging mode, this makes perfect sense. The charger is sending "noisy" DC to the batteries so the radio is being powered by this noisy DC current. Once the batteries are fully charge, the portion of the power supplied by the charger will be much less and the noise should be less as well.

How often do you transmit on the VHF when you're plugged into shorepower? In normal operation (underway) this shouldn't be a problem