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Old 03-09-2011, 08:16 AM   #1
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RFI Nois

As I understand it RFI is essentially is noise that is superimposed as a disturbance or a voltage transient on equipment. It can be impressed on the entire boat electrical power supply, or on data and signal lines that carry your GPS or navigation data between each other. This noise is then processed along with all the good data, and it will corrupt or degrade the processed information.

That being said.
After installing a new GPS and Radio.
*I now have a humm in my radio.

What would be the easiest way to track this down to eliminate the hum from my new radio?

SD
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Old 03-09-2011, 09:54 AM   #2
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RE: RFI Nois

SD, I guess I'd start with the grounds, since that is usually a good place to look.* After that, depower everything, turning devices and circuits back on one at a time to see if you can reintroduce the hum.* Flourescent lights onboard?* The ballasts are notorious for generating EMI/RFI.
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Old 03-09-2011, 10:09 AM   #3
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RE: RFI Nois

Do you think it could be Induced coupling interference?
*
Where*I may have electrical wires installed in parallel with other wires.

I am just thinking about possible issues to check on when I go to the boat this weekend.

I may have a Parallel run of my signal cable with my main power wiring.

SD
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Old 03-09-2011, 10:17 AM   #4
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RE: RFI Nois

Quote:
Delfin wrote:Flourescent lights onboard?* The ballasts are notorious for generating EMI/RFI.
Thes lights turned out to be the culprit on my boat.

*
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Old 03-09-2011, 10:27 AM   #5
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RE: RFI Nois

Quote:
skipperdude wrote:

Do you think it could be Induced coupling interference?

Where*I may have electrical wires installed in parallel with other wires.

I am just thinking about possible issues to check on when I go to the boat this weekend.

I may have a Parallel run of my signal cable with my main power wiring.

SD
Possible, and you can check out that theory by moving the wires and seeing if the hum changes in tone.* You should also check the wiring to the antenna and make sure what you have is matched to the new radio, and that if you have installed new coax the fittings are properly grounded.* A lot of times this is a process of elimination, but it is possible the radio has an issue as well.* If you still have the old, can you swap it out and see if the problem persists?* If not, you have the solution.

*
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Old 03-09-2011, 10:35 AM   #6
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RE: RFI Nois

As Carl on Delfin says, shut things on and off and see what happens.* We have found the inverter/charger can be a major source of "noise".** That would be my guess if you are plugged into shore power.
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Old 03-09-2011, 10:42 AM   #7
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RFI Nois

I was told that the best tool for tracking down the noise is to use a battery powered *AM radio.
The idea being that by holding the radio close to subject wiring and components that the radio will pick up the interference right away.

Lets say I track down the noise what is the best way to supressit.

I was* told something about crossing the wires at a 90 deg.

Or filter or capacitor of some sort.

SD

-- Edited by skipperdude on Wednesday 9th of March 2011 11:46:16 AM

-- Edited by skipperdude on Wednesday 9th of March 2011 11:47:37 AM
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Old 03-09-2011, 10:54 AM   #8
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RE: RFI Nois

Quote:
skipperdude wrote:

As I understand it RFI is essentially is noise that is superimposed as a disturbance or a voltage transient on equipment. It can be impressed on the entire boat electrical power supply, or on data and signal lines that carry your GPS or navigation data between each other. This noise is then processed along with all the good data, and it will corrupt or degrade the processed information.

That being said.
After installing a new GPS and Radio.
*I now have a humm in my radio.

What would be the easiest way to track this down to eliminate the hum from my new radio?


After many years in the electronics field, the word "hum" to me, is a 60 hz, low pitched sound, much like a human would make when "humming" a tune.

So - do you have a hum or do you have something better described as "static"?
What brand and model GPS and radio?
Does the noise go away if you turn the GPS off?
Is it only on certain channels or all of them?
Did you change any other wiring or just replace the existing GPS and radio using the same wires?
*
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Old 03-09-2011, 11:02 AM   #9
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RE: RFI Nois

Quote:
rwidman wrote:


After many years in the electronics field, the word "hum" to me, is a 60 hz, low pitched sound, much like a human would make when "humming" a tune.

So - do you have a hum or do you have something better described as "static"?
What brand and model GPS and radio?
Does the noise go away if you turn the GPS off?
Is it only on certain channels or all of them?
Did you change any other wiring or just replace the existing GPS and radio using the same wires?
*

I installed a Garmin 4208 with a camera and a connection to the flat screen TV.
With a new Icom M422.

All new wiring except for the antenna coaxel.

I just noticed the humm.**More of a buzz as*I was shutting things down after my crab trip.

I think everything was off but the radio. But I can't be sure.
*
Damm old age sucks.

Note to self make a note to self.

*Oh yea. I also hooked up the DSC between the GPS and The Radio.
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Old 03-09-2011, 11:48 AM   #10
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RFI Nois

My Garmin 5208 causes noise on channel 68 on my VHF. I verified that it also causes noise on a handheld and a portable AM radio. I'm working on it.

-- Edited by rwidman on Wednesday 9th of March 2011 12:49:18 PM
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Old 03-09-2011, 12:03 PM   #11
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RE: RFI Nois

Great.**We can compare notes on monday next.

I think the channel I was on was 16.

SD
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Old 03-13-2011, 05:44 PM   #12
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RE: RFI Nois

You might want to try snap on ferrite chokes where the power leads enter the radio. It could be some sort of ground loop.
Bill
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Old 03-14-2011, 06:05 AM   #13
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RE: RFI Nois

Quote:
Billylll wrote:

You might want to try snap on ferrite chokes where the power leads enter the radio. It could be some sort of ground loop.
Bill
That's not a ground loop.* A ground loop is where the grounds of different pieces of equipment are grounded at different places, resulting in a different potential and current flow from one ground to the other.

In the case of my plotters, the noise is eminating from the units themselves, not the power leads.* I have placed multiple chokes on the leads without effect.* If I hold an AM transistor radio near the screen of the plotter, I will hear the noise in the radio.

*
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Old 03-14-2011, 02:52 PM   #14
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RE: RFI Nois

Quote:
Billylll wrote:

You might want to try snap on ferrite chokes where the power leads enter the radio. It could be some sort of ground loop.
Bill
I found the source it is my refrigerator.

Now how do I stop the buzzzzzz!!!

SD

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Old 03-14-2011, 06:02 PM   #15
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RE: RFI Nois

Quote:
skipperdude wrote:
I found the source it is my refrigerator.

Now how do I stop the buzzzzzz!!!

Stop opening the door so often to get more beer....................Arctic Traveller

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Old 03-14-2011, 07:18 PM   #16
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RE: RFI Nois

Quote:
skipperdude wrote:I found the source it is my refrigerator.

Now how do I stop the buzzzzzz!!!

SD
What type, voltage, etc.?

*
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Old 03-14-2011, 09:28 PM   #17
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RFI Nois

I'd have to get the book. *it's on the boat.

It's just a Norcold 12 volt fridge. It also runs on 110 when hooked to shore power.

If this is not really going to interfere with radio reception I may try to ignore it.

It does keep the beer cold.

Trading one buzz for another

I need to see if it interferes on 12 volt or just 110.

I may just live with it.

There's just no beat. Can't dance to it.

SD



-- Edited by skipperdude on Monday 14th of March 2011 09:29:13 PM
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Old 03-14-2011, 11:32 PM   #18
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RE: RFI Nois

Do as you suggested and try to figure out if it is on AC or DC that the noise is created.
It may have to do with where the power is wired to it if it is noisy on DC.
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Old 03-15-2011, 04:19 PM   #19
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RE: RFI Nois

The controller box on the some Danfoss*units will cause a hum on the VHF radio.* I had an Adler Barber with a 15 year old Danfoss and the radio was all but useless when you transmitted on it.* Adler Barber was aware of the problem but their only fix was to put chokes on the line. They said the signal was coming through the 12V+ side.* That didn't work.

You might try a separate 12V battery and connect the radio both + and - to it to see if that is the problem.*

I installed a new cooling unit and the problem went away.
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Old 03-15-2011, 06:50 PM   #20
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RE: RFI Nois

If you're trying to filter out RFI with chokes, etc., you want to put them as close to the source (in this case, the refrigerator) as possible. Also, make sure the refrigerator frame is grounded.
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