Help- Loud Pop noises through computer speakers

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pro106import

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I am able to hook up a patch cable from the earphone jack of my BCD-396XT to my audio input of my computer sound card and hear the audio great through my computer speakers.But as soon as I hook up the serial port cable from the computer to the radio, I get loud pop noises whenever the radio mutes after a transmission. When it unmutes for a transmission, it pops briefly also. Then I am able to hear the audio fine until the transmission stops and the radio mutes, giving the brief pop noise again.
So a quick account of the event would be this:
Radio scanning- stops on active channel- unmutes so I can hear the transmission- POP- normal audio of transmission- transmission ends so radio mutes- POP

If anyone needs a sample, I can send a clip. I am using the Scanner Recorder Pro program to record and simultaneously log the radios data. But the pops are annoying!
Bob
 

W6KRU

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This has came up several times before on here. The way I understand it from previous threads, the scanner is turning the audio amplifier off and on to conserve battery power. You don't need to power the audio amp when the scanner is just scanning and not receiving anything. You can also hear this happening through the scanners speaker.
 

W6KRU

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Not quite - it's more like a ground loop problem. This question has come up so often that the solution in this thread probably should be added to the FAQ...

http://forums.radioreference.com/uniden-scanners/141725-bcd396xt-audio-popping-solved.html

73 Mike
Really? I don't understand that. If it was a ground loop problem, why do I hear it through the speaker in the scanner? I believe that the fix works when hooking the audio up to another amplification device/computer because several people have reported success but I think it has something to do with filtering the spikes out.
 

pro106import

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ka3jjz

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Hmm...perhaps your issue is different, Dan, but almost certainly pro106's is a loop issue between the serial cable and something in the earphone jack. 73 Mike
 

slicerwizard

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Hmm...perhaps your issue is different, Dan, but almost certainly pro106's is a loop issue between the serial cable and something in the earphone jack. 73 Mike
The issue is dirt simple - when you take the headphone jack's sleeve (which is not connected to the scanner's ground) and force it to ground through the programming cable, bad things happen. Without the protection resistors in the jack circuit, you'd probably blow the audio amp.
 
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