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EMI/Noise on new radio install.

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dancrosoft
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EMI/Noise on new radio install.

Post by dancrosoft » Wednesday, 09 September 2015, 19:20 PM

I have a 2011 F150 that had a Galaxy DX94HP in it for several years. The 94 developed some audio issues (TX/RX were fine but no sound from radio). I opted to use that as an excuse to upgrade so I purchased a Galaxy DX98VHP :). For some reason the 98 is picking up alot of noise from the truck that the 94 did not. For instance I can hear the whine of the alternator, as well as a hum when I turn on my headlights and or fog lights. Also strangely - when I use my blinker - the meter on the radio will swing with my blinker and I can hear it in the radio. The only thing that was changed was a new wire run - I moved from 10 gauge to 8 gauge wire on both the + and -. The wire was routed the same way as the old. SWR is also quite high as well - again same antennas - same ground plane. (I have not had a chance to take it to an open area yet so the SWR #s may be skewed and unrelated.) < I also think the SWR readings are skewed by the noise.

Thanks for any advice!

-- Wednesday, 09 September 2015, 22:09 PM --

In case extra info is needed:

Antennas: 2 x 4ft Wilson Silver Load mounted to toolbox with grounding strap on each mount that leads to a frame bolt in the bed. Conductivity tests good on my Fluke from the antenna base to a unrelated bolt in the frame under the truck.
Coax is a 75ohm 18ft run - I believe the COAX is the one that came with a dual firestik kit that I had prior to the WIlsons.

Radio wired directly to the battery with 8 Gauge/Copper ring terminals.
I ran an extra ground wire of 12 gauge to the chassis of the CB as a troubleshooting step. It did slightly reduce the noise.

Next thing I have thought about trying is ferrite.


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MDYoungblood
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Re: EMI/Noise on new radio install.

Post by MDYoungblood » Thursday, 10 September 2015, 14:23 PM

The very first thing to do is to make sure the SWR is right, changing radios should not have changed the SWR if they were right to begin with.
Now changing the power leads shouldn'tpick up any more noise than the ones they replaced, a quick check would be to unplug the antenna from the radio and if your still receiving the noise in the radio it is not antenna related.
I experienced this problem on one of my radios, figured out it was a grounded out RX wire in the microphone, replaced it with the stock mic and the whine and hum went away. Checked the power mic and it was a shorted wire.

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dancrosoft
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Re: EMI/Noise on new radio install.

Post by dancrosoft » Thursday, 10 September 2015, 19:07 PM

With further troubleshooting I found that the noise is really bad with the passenger side antenna hooked up. I will do some more detailed checking tomorrow but I connected the passenger size coax to the driver side and there was very little noise and no swing. (I am using truck off + blinker on as my test - with both antennas hooked up - there is so much noise that the needle swings to 4 or so) Hooking either end of the coax to the passenger side antenna makes it swing. I also tried switching antennas, both swapping and another set. At this point I believe my issue is either the ground strap or the mount. I have $ on the mount.

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Re: EMI/Noise on new radio install.

Post by 1206FL » Friday, 11 September 2015, 3:47 AM

Bond the exhaust to the frame with a ground strap. They sell the kits at most auto parts stores. But 1st get vswr corrected and the other issues may go away as well. You either have a bad connector or a bad impedance match from radio to antennas. The 4ft antennas may not be rated for much power either, not sure of the specs of the 4ft silver load antennas but I'm sure that they don't much power, normally the max power out of the antenna is over exaggerated by the manufacturer. Helps sales!! But IMO, just like MD stated get your vswr issue resolved. Are you using a known good external meter for the vswr readings. And yes an open field would def be better than parked in the yard in front of the house with all the surrounding stuff. 50-75ft all around is a good area to use. Open field like you said. Keep all doors closed and keep anybody away from truck as well. The receive on the new radio might also be a but more sensitive than the last radio. A ground loop isolator on the power leads near radio might help as well as ferrites, but again like said, this may all go away with a good vswr reading. DONT keep keying the radio if the vswr is bad.

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MDYoungblood
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Re: EMI/Noise on new radio install.

Post by MDYoungblood » Friday, 11 September 2015, 5:29 AM

Look at the nylon insulator washer, it may be cracked and causing the SWR problem, that would be the only thing that could go wrong on a mirror mount, (yes it's still a mirror mount even fastened to the side of a tool box, have installed them like that for years). Remember the coax has to be connected to both antennas, not one at a time or the SWR will show extremely high.
Bonding the exhaust was a big thing on diesel engine trucks and pickup, on some it did quiet some of the noise so give it a try, use a SS hose clamp on the tailpipe and a flat braided strap. You said on the "ShoutBox" that it had just come back from the shop so look around and replace any of the vehicles bonding that the shop forgot to put back on.

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Greg
"321, the Middle of Maryland"

23 AM "WORLD WIDE" 38 LSB

Strong Supporter of America's Original Homeland Security Act
The Second Amendment



Official Moderator - CBRT Complaint Department




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dancrosoft
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Re: EMI/Noise on new radio install.

Post by dancrosoft » Friday, 11 September 2015, 15:26 PM

I checked the bonding from the box to the cab and all tested ok. I replaced the COAX and rerouted it as well. I will put new mounts on it when they come in tomorrow. Will update in the am. (The conundrum here is none of this noise existed with the DX94.) If the issue persists after I replace the mounts; I am going to wire up my cobra 29 as a test. If I hear very little noise in the Cobra 29 - it mite be the radio.

-- Friday, 11 September 2015, 17:36 PM --

Am I correct that there should be absolutely no conductivity from the isolation washer up to the ground?

-- Friday, 11 September 2015, 21:02 PM --

Another interesting thing i noticed was when my lights are on - the noise is extremely loud. I recently converted all my bulbs to LEDs - I wonder if they are emitting EMI...

-- Saturday, 12 September 2015, 17:14 PM --

Update if anyone is following:

I installed ferrite chokes on all wires going to my LEDs. = Lower swing when blinker was on and overall lower noise when all lights active.

That however did not address my whine which I assume was alternator. I installed a Pyramid NS50. It is not ideal as the AMP rating on this thing is less than what the radio needs. However I think it will get me through my trip as long as I leave the power mid ways. I did not expect much from this thing but it completely eliminated the high pitch squeal when keying the mic. The next step is to find one rated at 50AMPs or build one myself. It looks like a fairly simple device. I have some ferrites coming in tomorrow that are a composition designed for Higher Frequencies - will put those on and report back.

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