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VHF Radio Interference

Old 04-02-2003, 04:10 AM
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NPH
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Default VHF Radio Interference

When ever my motor is running I get a popping or crackling noise on my vhf radio. It does matter what chanel I am on, when ever I am recieving the popping is there.

The boat is a 25' pontoon boat, it has an Icom M45 radio, shakespear antenna, and a Merc 90hp 2stroke classic motor.



I have removed the depth finder so I know it is not picking up from that. I have tried to move the antenna and that does not change the noise. I have added a suppresor filter from Radioshack but that has not effected it.


Can anyone help me fix this problem?

Scott
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Old 04-02-2003, 05:35 AM
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Default VHF Radio Interference

.
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Old 04-02-2003, 05:47 AM
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Default VHF Radio Interference

There's a couple of easy things to try: first, try a portable vhf radio. If the 2nd radio has a problem also, then it clears the original radio from having a defect. Second, disconnect the antenna from the fixed radio. If the noise is still there, that tells you that the noise is coming down the 12v line. If the noise goes away, check out that motor for arcing plug wires, etc.
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Old 04-02-2003, 06:14 AM
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Default VHF Radio Interference

I also have a handheld on the boat,

There is no problem with the handheld. There is no reception with the antenna off.

I can see no visable problems with the motor, (It was also serviced at the end of the season last year, carbs rebuilt because it was running rough) The motor is a 2002, with 125 hours on it. The problem has been there since I installed the radio, at about 3 hours.

Any other suggestions?
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Old 04-02-2003, 06:59 AM
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Default VHF Radio Interference

Check to see if the lead to the tach is close to the power supply to the radio. Check if any wiring is close to it (with in reason) and move if possible. Also, check the ground connection on the radio and your antenna and insure it is solid. Sometimes a bad ground can cauise noise as no shield is present to stop it or the radio is grounding through the antenna or the case it self. If you cannot figure it out I would suggest a noise filter on the power supply. They also have high suppression plug wires but that is probably over kill.

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Old 04-02-2003, 07:24 AM
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Default VHF Radio Interference

All good advice from the guys above.

You mentioned "while my engine is running".

Try looking around for either a bad spark plug (cracked porcelain) or even worse a bad spark plug wire.

A good way to find a bad wire is to run the engine in the dark and see if you notice spark jumping around?????

Any interference that you will pick up through your antenna is going to be almost impossible to get rid of......you have to get rid of it at the source.

Good luck..............Booby

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Old 04-02-2003, 07:27 AM
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Default VHF Radio Interference

Also check the connections on your alternator/starter motor. Remove them, clean them, coat with a good electrical anti-corrision stuff, then tighten back up. That is where most noice comes from on an engine, the alternator. The second thing to do if that don't work(and above doesn't work), is replace your spark plugs with the noise reducing ones (they have a resister ones on/in them).

But first, check all yoru connectors, make sure they are tight and make sure all your stuff is grounded good.

Birdman, Capt of
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Old 04-02-2003, 07:52 AM
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OK,

I understand most of the advice I am getting, except the ground issuse.

I have run new power leads to the helm #6 wire, both Hot and ground. This goes into a fuse block. The radio comes out of that fuse block.
This did not change the problem at all.

Last year I did add a Radio Shack filter between the power supply and the radio. This did not change the problem at all.

I have not grounded the antenna, I do not know how. It is a Shakespear 5101. It is on a stainless mount, that is mounted to the aluminum railing on the boat. I tried removine the antenna from the bracket, there was no change in the popping sound.

Do I need to ground the antenna if so how do I do this. Do I need to grund the body of the radio?

As soon as I can get out to the boat after dark, I will run the motor with the cowling off to see if I see any sparking from the wires. Ihave pretty much ruled out bad plugs, as they were changed 3 times last year due to the motor running rough at idle (Could this be another sign of bad plug wires???)

Thanks for all of the advice.

Scott
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Old 04-02-2003, 08:02 AM
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Default VHF Radio Interference

I would first suggest that you determine if the noise is coming from the engine. Vary the engine speed an note if the noise frequency changes with speed. If it does, I think Birdies suggestion of usine noise suppressor spark plugs is a good start. The plug number will have an R suffix.
If it is not the plugs, than there are some other good suggestions (above) to try, but it could be a nasty problem.
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Old 04-02-2003, 09:17 AM
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Default VHF Radio Interference

If you spliced a pl259 connector on your antenna just make sure you have the outer shield braid connected good. If it came that way and you did not cut the cord then it is probably fine. The post about the starter and alternator was a good one as we used to sell large noise filters (large capacitor is all it is) and connect them to the alternator. You have an outboard so that is not possible but a plug wire leaking is. You can also run a seperate power supply (battery) and connect it just to see if it goes away. If it does then probably , given all grounds are good, you will need to install a filter. If it is through the antenna then the ignition components (plugs, wires, etc..) would be a possible suspect.

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Old 04-02-2003, 03:14 PM
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Default VHF Radio Interference

You say the antenna is mounted to a railing via a SS mount. Is the railing grounded at all? Probably not. I bet it is screwed/bolted into fiberglass only.

Anywho, as a test to see if that is the problem, just run a peice of wire from your NEG/Ground bus bar or battery's neg terminal, to the railing in question. Does problem go away?

Grounding what the antenna is mounted on is not always necessary but I've seen ungrounded ones cause problems. Don't know why...? But it's easy to test.

My 1st guess though, if the noice is occuring only when motor is running, is that it's the alternator.

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Old 04-03-2003, 06:12 AM
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A few more things to try and all are free and easy.

A good way to tell if interference is coming from the plugs or alternator is: while your at the dock and in neutral run your engine about 3000 rpm +/-.
Listen to your radio for interference closely.
When you turn your key off and if the interference goes away INSTANTLY then it's probably plugs.
Now try it again and if you hear the interference continue AFTER the key is off (maybe a second or 2) it's probably the alternator.

I don't know what antenna the 5101 is but if it is one of their marine fiberglass antennas no need to ground it. They have what is called a "false ground" built into them.

One more freebee I would try and that is to take a 12 volt battery with NOTHING hooked to it. Run you radio power cords to it (short as possible).....of course red=positive and black=negative. Ground the chassis of your radio to your motor.
This will bypass all the other junk that is in line and if it was my radio I would hook it direct to the battery when finally install and bypass your fuse block but make sure you do have a fuse for the radio.

If all that fails I would try a friends radio hooked the way you would have it hooked inyour boat and see what happens.
Good luck.............Booby
Keep us all posted.....I am curious.

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Old 04-03-2003, 10:13 AM
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Default VHF Radio Interference

Thank you everyone for the suggestions. I am hoping that it is the plugs, they are not "resitor plugs" I can get them for my motor, but they are $12ea. I have them on order and as soon as they are in I will try them.

I hope to splash the boat sunday, static or no static.
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Old 04-07-2003, 09:12 PM
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Did you ever get the noise out of the radio.....just curious?

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Old 04-08-2003, 10:09 AM
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Just for fun...

The first viable radio transmitter was a spark gap transmitter.
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Old 04-08-2003, 10:15 AM
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Booby Trap

I am still waiting to get the new plugs in. The Marine store I deal with did not have them in stock. (Could always go to BoatUS etc, but the local guy always takes good care of me, so I would rather give him the money)

I did put the boat in the water on Sunday, so now it will be a littler hard to replace the plugs.

I will let everone know as soon as I change them.
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Old 04-08-2003, 11:29 AM
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Try www.sparkplugs.com for those plugs. You'll have them in three days!. Good Luck!

Boston Whaler, "MUMBLER", 24' Outrage, twin 175 HP Evinrude Ocean Pros. Snowball, the cat...
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Old 04-12-2003, 07:10 PM
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I got the plugs in earlier this week, put them in today and took the boat for a ride. No More Clicking noise.

Tell me why $20,000 dollars for a new boat, and they can not put in the right spark plugs.
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Old 04-12-2003, 08:25 PM
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Ahhhh, silence is golden.
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Old 04-14-2003, 04:57 PM
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Well that was cheap and easy and glad you got it OK.

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