Keying mike kills truck

[dirtcrew51m]

Hello, I have a 95 F250 w\7.3 powerstroke, with a Cobra 148 basically stock, no amp, when I key the mike, it kills the truck, I also put my other cobra 148 in the truck, same thing, this has never happened on my gas trucks, I had a cobra 23 in the truck with no issues. I put ferrite on the antenna at the radio and on the throttle position sensor, which is located on the throttle pedal, helped some, truck is drive by wire, I have the antenna wire going to the rear of the truck, is there anywhere I could put more beads, or shielding? I was thinking at the end of the cable at the antenna, or more on some feed wires to the ecu and injector drive unit.

 

[Robb]

Sounds like either a factory omission of proper shielding, or some shielding is defective or missing due to mishandling. It would be essential for any vehicle that has been designed as 'drive by wire' to keep ANY freq of RF out of its system to keep on working properly.

Sooo, this is a case of a factory defect (doubtful), or some shielding has been compromised.

Are there any service bulletins on this vehicle for this issue?

 

[Decoder]

Wire it to the battery maybe the circuit you are using goes to the injector kill circuit. I own a 7.3 too. it funny when your going down the road at 65 and key up the radio

 

[midnight special]

need more info,,,, where is power for radio coming from, where is ground for radio connected at,,, is antenna ground good and not coming back down coax to radio,,, what kind of antenna,,,,do you have coax running out from back of cab or is it run up under dash out of cab?,,,,

 

[dirtcrew51m]

Decoder you have this issue too? Both ground and pos direct from battery, antenna wilson 4', 18' or so of cable, swr around 1.3, 1.4, radio and antenna are tuned, I first had it under the dash, but now it is directly to the back.

 

[M0GVZ]

Decoder you have this issue too? Both ground and pos direct from battery, antenna wilson 4', 18' or so of cable, swr around 1.3, 1.4, radio and antenna are tuned, I first had it under the dash, but now it is directly to the back.

RF choking needs to be done outside of the vehicle at the antenna, not the radio end but if you're using a fixed mount you shouldn't need to. By doing it at the radio end you're still going to have RF being radiated inside the vehicle by the coax. You also can't just use any old ferrite because they all work at different frequencies. It needs to be Mix 31 or MIx 43. If you're using a magmount your only solution may be drilling a hole.

On modern vehicles you have to put the ground wire to the body of the vehicle, ideally as near to where the main battery earth cable connects to the body as possible. This is because of the smart charging circuits now employed and connecting directly to the battery negative terminal screws that up.

 

[dirtcrew51m]

Thanks, I will play around with grounds, I was looking at some split 43\44 beads at Radio Shack. As far as a smart vehicle, I dont think my truck qualifies.

 

[M0GVZ]

Thanks, I will play around with grounds, I was looking at some split 43\44 beads at Radio Shack. As far as a smart vehicle, I dont think my truck qualifies.

If you're getting split beads get the large ones you can get 4 or 5 turns of coax through. The more turns the higher the choking. 4 or 5 turns through a 43 will give more choking than six or seven just clipped on the coax. Mix 61 ferrites are extremely good if you're only using the antenna on the 11/10m bands.

 

[psycho]

A stock Cobra 148 kills the truck on transmit.......yeah right.

 

[dirtcrew51m]

Ya. One is stock one has been tuned. No other mods done to the radios. Tuned radio puts out no more than 5w on am and around 13 w or so on ssb.