Idle drops when keying cb radio mic

[mike60retired]

2000 superduty 7.3.....I have a professionally installed and tested CB radio in my truck that has worked for many years. Recently when keying the mic the engine rpm drops to about 500rpm. when releasing the radio mic key the rpm returns to normal.
I took the truck to a cb shop today. They installed a test cb radio and antenna. The test system had the same affect on the engine RPM. Is there a Ford noise filter on the computer or some other ford electrical component that may need to be shileded or replaced?

[Deeslfxr]

Did the test system use the same coax cable as your regular system? Maybe cable is routed too close to the PCM?

[mike60retired]

The test system used a maganitic roof mount antenna with its own coax

[READNECK]

did they use the same power wire and ground as your current setup?

[mike60retired]

no, they used a different power source. they plugged into the cig ligher.
My power comes from the fuse panel

[mike60retired]

to test, I ran power directly to the battery with no positive change

[READNECK]

it really sounds like a ground issue to me. i'm sure some one with more knowledge will come along soon and help you good luck.

[jesilvas]

maybe you got your radio tuned and it's drawing so much power to transmit your truck is lugged down lol
but seriously, no clue. mine doesn't do this and mine runs in by the pcm, is grounded to the frame and mounted on the mirrors. power is from a tap a fuse on the radio fuse so that it's shielded

[superduty4x4]

Try re-routing the coax cable. Someone on another site I frequent had this problem and it was solved by re-routing the coax.

[Deeslfxr]

Originally Posted by superduty4x4

Try re-routing the coax cable. Someone on another site I frequent had this problem and it was solved by re-routing the coax.

Yup, I have to agree.