Buzzing when speaker output is connected to PC

[snipes420]

I have a problem with a loud buzzing or humming when hooking my radio's speaker output to my computers mic or linein input. I can connect the radio to various speakers and it performs clearly.

The Problem radio is a Kenwood TK-730.
The computer has four sound cards with the first one's input in use by a Vertex FTL-2011 without issue.
I am suspecting a grounding problem but I'm not sure where it would be.

 

[ProScan]

I have a problem with a loud buzzing or humming when hooking my radio's speaker output to my computers mic or linein input. I can connect the radio to various speakers and it performs clearly.

The Problem radio is a Kenwood TK-730.
The computer has four sound cards with the first one's input in use by a Vertex FTL-2011 without issue.
I am suspecting a grounding problem but I'm not sure where it would be.

This has been discussed multiple times on RR. It is caused by a difference of potential of ground points. The easiest fix would be connecting an audio isolation transformer between the scanner output and the sound card.

 

[snipes420]

I have a bunch of spare dial-up modems with this part on it. LCT0150 and ATS-273B
The spec sheet says it is 1:1 windings. Could this be an acceptable part for this purpose?

 

[ProScan]

I have a bunch of spare dial-up modems with this part on it. LCT0150 and ATS-273B
The spec sheet says it is 1:1 windings. Could this be an acceptable part for this purpose?

It will work. There is a impedance mismatch which results in attenuation so you will have to crank up the scanner audio up a few notches.

 

[snipes420]

Thanks for the tip! I wired a transformer between the radio and PC and now the buzzing is gone