I have put up my feed SIM Montreal Fire (Montreal, Quebec, Canada). There is a constant noise which is like an echo or a feedback noise. The connections are to the external speaker jack of a BC796D into the mike jack of the computer. These are the only connections available to me. Can anyone suggest how to get rid of this noise. Thanks in advance for your help.
Echo/Noise
- Thread starter mtlfirebuff
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kb0nly
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Get rid of the speaker connection and go with flat audio it will sound much cleaner. If you listen to my feed for Lincoln county MN or Brooking county SD those are my BC796 and BC785, they both used to have a noise like you describe until i modified them. I wrote up the mod on here but searching i can't find it, so i will repost i guess.
The BC796D and the BC785D have a tape/record jack output on them that is independent of the volume control, the only problem is its controlled by the scanner, switched on and off, this creates a delay of about 2 seconds of missed audio of every transmission and it also creates a loud CHUNK sound as the scanner cycles this output on and off by turning the audio amp on and off for that output.
With the help of another ham to find the right tap point i came up with a mod to eliminate these problems and bring out an audio source that is constant and not affected by the volume control.
Take the covers off... See the larger multipin connector in the center, J6 with one blue wire at pin 1 and the rest are white? You want to tap off that blue wire. I flipped mine over and cut the trace feeding the tip contact (it's a stereo jack with the tip and ring fed the same audio source) on the Tape/Record jack then soldered on a jumper from that to the pin 1 of J6, the one with the blue wire. The trace is right behind the solder point, just under the lip of the back panel.
Optional but also a good idea, i cut the traces on either side of the pin for the ring contact on the jack, the Tape/Record jack is a stereo jack, so i isolated that contact so i can insert a mono or stereo plug and it doesn't matter anymore, also no chance of mixing in the switched audio source either. You can also just cut the trace forward of the ring solder point but then the ring and tip are still connected to each other, so if you use a stereo plug on the other end and using the mic jack on a sound card the mic bias voltage on the ring will be shorted to the tip, causing an audible buzz on most soundcards.
Another option is you could also follow the trace from the ring contact over to about the center of the board where the electrolytic cap is on the other side feeding that trace from the audio amp, if you removed the cap and soldered a jumper from that point to pin 1, the blue wire, it would feed both the ring and the tip of the tape/record jack with the same audio and you wouldn't have to cut any traces, just remove one component.
I figured I would do it this way so that if I ever wanted to add a discriminator tap I could use the ring of the tape/record jack to bring out a second connection as well without drilling any holes to add a jack. Then if i ever want to return it to stock i just have to repair the cut traces.
The BC796D and the BC785D have a tape/record jack output on them that is independent of the volume control, the only problem is its controlled by the scanner, switched on and off, this creates a delay of about 2 seconds of missed audio of every transmission and it also creates a loud CHUNK sound as the scanner cycles this output on and off by turning the audio amp on and off for that output.
With the help of another ham to find the right tap point i came up with a mod to eliminate these problems and bring out an audio source that is constant and not affected by the volume control.
Take the covers off... See the larger multipin connector in the center, J6 with one blue wire at pin 1 and the rest are white? You want to tap off that blue wire. I flipped mine over and cut the trace feeding the tip contact (it's a stereo jack with the tip and ring fed the same audio source) on the Tape/Record jack then soldered on a jumper from that to the pin 1 of J6, the one with the blue wire. The trace is right behind the solder point, just under the lip of the back panel.
Optional but also a good idea, i cut the traces on either side of the pin for the ring contact on the jack, the Tape/Record jack is a stereo jack, so i isolated that contact so i can insert a mono or stereo plug and it doesn't matter anymore, also no chance of mixing in the switched audio source either. You can also just cut the trace forward of the ring solder point but then the ring and tip are still connected to each other, so if you use a stereo plug on the other end and using the mic jack on a sound card the mic bias voltage on the ring will be shorted to the tip, causing an audible buzz on most soundcards.
Another option is you could also follow the trace from the ring contact over to about the center of the board where the electrolytic cap is on the other side feeding that trace from the audio amp, if you removed the cap and soldered a jumper from that point to pin 1, the blue wire, it would feed both the ring and the tip of the tape/record jack with the same audio and you wouldn't have to cut any traces, just remove one component.
I figured I would do it this way so that if I ever wanted to add a discriminator tap I could use the ring of the tape/record jack to bring out a second connection as well without drilling any holes to add a jack. Then if i ever want to return it to stock i just have to repair the cut traces.
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