Truck electronics Interference

[uriedog]

I have an interference issue in my truck not sure how to get rid of it, maybe some one here as some input.

I have an Yaesu FT-8800 mounted under my dash. Every time I key up the mic my after market fuel pressure gauge drops to 0, and my car stereo does all sorts of weird stuff. Changing stations, switches to different menu modes, even shuts off.

I moved my fender mount antenna to the other side of the truck (away from the fuel pressure sender) , but that does not seem to have helped. Wondering if there is some sort of filter I could put on the coax. Or maybe its some sort of buig RF leak.

 

[krokus]

Does the coax route along the wiring for those items? How about the Yaesu's power lead? Either one could be imparting RF onto the other electronics.

I am assuming you have the Yaesu grounded directly to the body or the battery.

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[HDMechanic]

What make of vehicle is it??

 

[VE6E0]

Can you try different power levels? Different bands, too. You can try makng up a common choke filter for the power leads, but I suspect it is radiated RF getting back into the electronics, especially the stereo.

 

[uriedog]

2001 Dodge Ram 2500 Diesel

The + and - go direct to the battery, I am going to try running the coax through a different hole in the fire wall today. Although it will be really hard to keep it away from the radio. The strange thing is that the radio did not affect anything when I had it mounted in my other truck

 

[smason]

Make sure your antenna mount is well grounded to the truck body.
How's your vswr?

 

[uriedog]

The antenna is deffinatly well grounded. I do need to check my SWR, Although it happens at all frequencies and VHF UHF

 

[mmckenna]

Try moving the power feed ground from the battery negative post to a ground somewhere else.

Check your coaxial cable and all connections. If you are using low grade coax or it is damaged, it can leak and cause issues. SWR isn't necessarily going to tell you this.

Check all the other wiring. Might not be your two way radio, but could certainly be aging electronics in your truck, corroded connections, etc.

Location of your antenna? Get it up on the roof top, even with a magnetic mount, as a temporary test. Could be too much RF is getting into the broadcast radio through it's antenna.

Grounding. Ground your radio AT the radio. Don't rely on long power feeds to the battery. Run a short jumper from the radio chassis to a nearby ground inside the cab. I had an old VHF radio that was mounted near the front of the truck bench seat. I could knock it out by sliding across the seat and building up a static charge.

 

[uriedog]

the antenna was on the opposite side from the stereo antenna. (that's where it was for years on the other truck) I moved it over beside to get it away from the sender for the electronic fuel pressure gauge.

I will try the jumper ground, and check the coax to be sure its not loose or cracked. Should be fine though as it is brand new. And I would asume fairly quality as it came from NTF and was expensive.

 

[wrc1045A]

Uriedog,

I would try a few things before I started changing things. Try to use a battery or jumperpack to power the radio directly (closer to the radio the better). try to key up to see if the problem exists. If it still does it is likely RF and not power related. Still with the external battery or jumper pack connected tot he radio take a spare antennae routed away from the current antennae lead path (loosely, on the seat or what ever) and try to key up again to see if the problem exists. This will bypass any uneccessary work that might not fix the issue above. This should tell you in two easy steps. Another issue is that during the installation on the radio a wire or connector was loosened or moved. Sometimes a connector with be jarded loose and doesn't seat all the way. Just my two cents

 

[mmckenna]

the antenna was on the opposite side from the stereo antenna. (that's where it was for years on the other truck) I moved it over beside to get it away from the sender for the electronic fuel pressure gauge.

Uh, OK, this would be what I'd address first. Move it back. If it worked there, other than affecting your fuel pressure sender, then that's a good sign. The issue isn't with the radio, necessarily, but lack of shielding on the fuel pressure sender and wiring.

Putting the transmitting antenna so close to the broadcast antenna is going to cause issues, as you've noticed. Running 50 watts out an antenna too close to the broadcast radio antenna is going to flood the receiver with way too much energy. You are fortunate that what you are experiencing is all it's doing. You run the risk of frying the receiver if it gets hit with too much power.

So, I'd move the antenna back, if that is where it worked. Then replace the fuel pressure sending wiring with something that has a grounded shield.

 

[uriedog]

OK so I went out and grounded from the radio case to body directly behind the radio. That seems to have cleared up the interference with the fm stereo. Now just need to sort out the sending unit for the gauge.

The sending unit has a ground that runs direct from the sender, and a signal wire that runs to the gauge. Tomorrow I will try and get the antenna wire further away and see what happens.

Oh by the way. I appreciate the help so for, never would have thought to ground the FT-8800 case

 

[mmckenna]

The sending unit has a ground that runs direct from the sender, and a signal wire that runs to the gauge.

That isn't the same as having a shielded cable. The cable from the sender to the gauge can be acting like an antenna and absorbing enough RF energy to cause the issue.

Relocating the coaxial cable will be a good start, but that may not be where the issue is coming from, it may be coming directly from the antenna itself. Short of relocating the antenna, it may not fix it.

Finding a shielded cable would be a likely fix for the sender. You'd need to ground one end of the shield to reduce the amount of RF getting into the gauge.

 

[robertmac]

For everything that you want and need to know and more, see www.K0BG.com

 

[HDMechanic]

Sorry for the late response. Your never going to get away from this issue. Its a Doge issue that is in most makes and modles. I belive its something to due with the fuel injector ecm. I know a couple of ham operators with Dodge pickups that have the same issue. I even notice if I pass a Doge and am on the right frequncie range I get wicked noises from them.