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VHF Distortion problem w/ new Furuno

Old 02-03-2003, 05:51 PM
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Default VHF Distortion problem w/ new Furuno

Yesterday I noticed when I keyed my microphone on my Standard VHF it would distort my furuno 600--put red columns up the screen. I figured it was my power source for the furuno. I had the Furuno hooked to my fuse buss. Today I moved the power for the furuno directly the battery--same result. The power wire for the furuno is shielded, but it runs parallel with the vhf antenna wire. I am limited on where I can run wires and don't have much of a choice. I also tried the additional ground on the furuno itself to no avail.

I did notice the distortion only happened on High power not Low Power when you transmist on the VHF. Anybody got a clue????????????
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Old 02-03-2003, 10:07 PM
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Default VHF Distortion problem w/ new Furuno

One thought is the connector on either end of the VHF antenna cable is not making proper contact with the braided shield under the outer insulating jacket?

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Old 02-04-2003, 03:58 AM
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Default VHF Distortion problem w/ new Furuno

I have seen this happen before. It sounds like an antenna probelm. On the boat I was on it effected everything from the depth sounder and GPS to the autopilot.
The simplest test you could try would be to plug in another antenna.
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Old 02-04-2003, 10:32 AM
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Default VHF Distortion problem w/ new Furuno

How many feet distance is between the middle of the vhf antenna and the furuno?
In any case, try a small gel cell battery right at the furuno. This will prove or disprove if the vhf energy is coming up the power wiring.
It makes a lot of sense that high power causes a problem and low power does not. Imagine what a 150 to 200 watt transmitter will do!!
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Old 02-04-2003, 11:00 AM
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Default VHF Distortion problem w/ new Furuno

It may be a lot simpler than its trying to become. First, pull out your coax cable to the radio and check every inch of it for a nick down into the woven shielding. I suspect you're going to find either a nick or a scrape from when it was pulled in there. If you don't find anything wrong with the cable try this; cut off the existing PL-259 connector and put a new one on. If you've still got nterference then pull the transducer cable and check it for nicks and such. Finally, if there are no nicks and the new connector doesn't do it, go to whatever lengths it takes to get the two cables away from each other. Oh, and ou might want to put a power conditioner on the feed line for the fish finder.

Thom

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Old 02-05-2003, 01:10 PM
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Default VHF Distortion problem w/ new Furuno

Follow Thoms advice 1st. I'd doubt it has anything to do with the power wire or feed at all. Nine times out of ten, a "leak" of this sort is a grounding issue, many times due to a bad connector whcih is why Thom has your checking changing them. If those don't work, you may very well have a "Bad" radio which is leaking HF and needs repaired. This is assuming two things though, 1, your radio is mounted near your Furuno and 2, your VHF antenna is ok (not broken, is a VHF antenna in first place?...).

Again though, almost always, it's a GROUNDING issue. Check your grounds for a GOOD SOLID ground all the way back to the battery terminals and/or grounding isolator (if you have one?).

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Old 02-05-2003, 09:20 PM
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Default VHF Distortion problem w/ new Furuno

how close are they if there really close together it could be coming right out of the radio being it only happens on high if there was a problem with the sheilding on the antenna cable it would happen even when the radio is on low
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Old 02-06-2003, 04:33 AM
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Default VHF Distortion problem w/ new Furuno

I have the same problem, don't have any nicks in the cables. I figured it was because the antenna is on the side of the boat and not on top is the problem.
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Old 02-06-2003, 05:22 AM
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Default VHF Distortion problem w/ new Furuno

Look very closely at the upper left corner of this picture:



What you are seeing is the base of a Shakespeare 5225 antenna that is mounted about 10" behind a Furuno 600L. The coax cable from that antenna was run through the same wire supports as the transducer cable. That was the third antenna that had been located in that position during the time that the 600L was mounted where you see it. I never had any problem with streaks, blips, or other odd stuff when using the radio.

Thom

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Old 02-06-2003, 01:41 PM
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Default VHF Distortion problem w/ new Furuno

Well done Thom!!

You have a nicked or broken cable, bad connector, or grounding problem. I'd put 3/4 of me bet on grounding.

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Old 02-06-2003, 11:50 PM
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Default VHF Distortion problem w/ new Furuno

Thanks for the honey hole Thom.
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