RFI on VHF Radio

[tybee22]

I have a popping noise on my VHF that can not be squealched out completely. The cause is from my Air-X wind generator.

Is there a filter or choke that can be installed to eliminate this problem? I have readthat twisting the leads can eleminate this problem, but really don't want to pull all wires back to pole mounted wind turbine and re-pull after twisting. Big Pita

Any info or advise will be welcome, I have done some research on this, but am challenged on the technical info and jargon and the install process or devices to use

[Nemo55]

A Capacitor installed on the power lead of the radio and case grounded to the radio Mounting bracket may do the trick.

[Nemo55]

Another possible solution is to power the Radio directly from the battery,,as the battery will act like one giant capacitor.

[Wotname]

Try some ferrite beads on the generator power leads as close as possible to the generator. See Ferrite bead - Wikipedia, the free encyclopedia

If that doesn't do the trick (and you have tried Nemo's advice), you might have to open up the generator and start adding capacitors across the output wiring.

[goboatingnow]

Id want to put a scope on it first, wonder what characteristics it has, ( its opening the squelch mind you, so it must be big).

Dave

[tybee22]

Thanks for the quick replies folks, but as I started to run a direct wire to radio from battery I was shutting power down to each system one by one and discovered the interferance is from the MPPT 250 charge controller used in my solar system, not the wind generator.

When I removed the fuse from that systems circit all RFI stopped. I blamed wrong devise. I have contacted BZ Prouducts for solution and am awaiting a reply from them.

Does anyone know of a way to eliminate RFI from this type of source?

[goboatingnow]

This is most likely a harmonic of the switching frequency used in the MPPT controllers. It is probably quite a high frequency. Ferrite beads are your friend. ( it could be air coupled , if the two devices were close). It can be hard to remove it completely.

Make sure the VHF has a good ground and supply , preferably direct to the battery ( with breakers or fuses).

dave

[Wotname]

Originally Posted by goboatingnow

This is most likely a harmonic of the switching frequency used in the MPPT controllers. It is probably quite a high frequency. Ferrite beads are your friend. ( it could be air coupled , if the two devices were close). It can be hard to remove it completely.

Make sure the VHF has a good ground and supply , preferably direct to the battery ( with breakers or fuses).

dave

Can't argue with this advice and if it is air coupled, confirm if it is being picked up by the VHF antenna or via the coax or direct into the radio etc; then relocating the offending items (controller, coax, antenna, radio etc) or shielding the controller.

But I agree with Dave, go the ferrite way first as mostly the RFI is radiated by the wiring.

[tybee22]

Will be researching ferrite beads, any suggestions of size or type to use. I think I will also move radio to differant location as it could very well be air coupled as all wiring, radio and antenna leads are in the same cabinet in very close proximitry to each other. This is not by my design, it is how the set-up was when I bought the boat. Only thing I have done differant was to install charge controller when I upgraded the solar panels as old one was not big enough. The solar system circut does not run through the main system, but is isolated from eveything and sepperatly fused with out-put back to house bank and divert to engine bank.

[Rhapsody-NS27]

Originally Posted by tybee22

I think I will also move radio to differant location as it could very well be air coupled as all wiring, radio and antenna leads are in the same cabinet in very close proximitry to each other.

This was about to be my advice but you're already on it. Moving the radio (and cables) might help reduce or eliminate the issue.

Let us know how it goes.

[goboatingnow]

This is quite a complex topic, so a few rules of thumb,

In general try and get at least one turn through the ferrite, and size the ferrite as close as possible to facilitate that

Select a ferrite with the highest impedance at the desired suppression frequency, since you will not have an idea, its a hit and miss affair.

It may take multiple ferrites to have an effect.

The signal could be coupling in via the Mike cable. does the if its disconnected does the squelch still open. PWM switching frequencies have risen to about 400Khz, so it will be some harmonic of that but hard to say, buy a selection of ferrites they arnt expensive. Put them on the VHF power leads close to VHF
put them on the input leads and output leads of the MPPT controller again close to the controller.

The simplest , but least effective are "clamp" type ferrites that dont require turns or the wire to be disconnected to fit them. buy a few an try them, its a bit hit and miss, but without a scope or better yet a spectrum analyzer its hard to get quantifiable data.

Put them on the mike lead ( if possible).

dave

[tybee22]

I'm certinally getting some great advise from you folks THANKS. Will be going to shore to pick-up wire and antena lead to relocate radio. Only marine electronics shop in Key West closed years ago so will source out some of the local hams for advise. If that fails I will drive up to Marathon and see the guys at he shop up there, 45 mile trip each way.

Meanwhile I am certainly getting an education as I reseach the ferrite bead solution. Wil post results as I have them. Once again thank you for all the information, tips and suggestions

[Paul Elliott]

Here's a link to a presentation I recently gave about SSB and satphones, including a section on EMI: SHTP Communications 2012.

About halfway through it I give some details on appropriate ferrites and their application. The particular ferrite I mention is optimized for SSB frequencies, but is still very effective in the lower VHF range, where you are having the problem.

[mrm]

Originally Posted by tybee22

Meanwhile I am certainly getting an education as I reseach the ferrite bead solution. Wil post results as I have them. Once again thank you for all the information, tips and suggestions

Had a similar problem with a noise from my laptop blanking weatherfax reception on my el cheapo SSB receiver. It turned out the noise was being coupled via audio cable. Took a picture of my solution for you. Works very well.

As advised already, try to get more turns through the ferrite ring. The reason (in very simplified terms) is, that the 'resistance' presented to RFI is proportional to a square of a number of turns. Good luck