Just a tip if your scanner is acting as a microphone.

VynylScratch

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These are some of the issues I am talking about if the title confuses you.


I had to setup my stream PC again after SSD failure and I was setting the volume for the feed when I heard a thump sitting it down on the table, I decided to tap on the case and heard it echoing back through the feed. This has happened before but I waived it off because I was not streaming just archiving. It turns out the "Microphone Boost" was set higher than +0.0 dB in the sound settings for my input device. In my case it was around 28 dB or so. Try adjusting that if this is happening for you.

mcb.jpg
 

jonwienke

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You're using your computer's microphone to pick up the scanner's speaker, rather than the wired connection. Or else you have the mic and line-in actively recording. Disable the mic in both the recording and playback mixer settings.
 

VynylScratch

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You're using your computer's microphone to pick up the scanner's speaker, rather than the wired connection.
Not in my case, the scanner is feeding with a standard 3.5mm aux cable to the microphone port on the laptop as there is no line in. The laptop disables the built in mic when a wired mic is detected. That could be the case for a few people potentially. Actually feel lucky to have a laptop with mic in since so many are now TRRS only.
 

jonwienke

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If you're picking up ambient audio, the laptop mic isn't being disabled. The scanner isn't capable of being a microphone.
 

VynylScratch

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I'm not picking up ambient audio. If that was the case I would be hearing birds and myself. This is not meant in the sense of being an actual microphone but instead picking up noise from the body of the radio its self.

The scanner can't be a microphone however the speaker can act as one as can be read here.

Furthermore my video will disprove the statement that the "laptop mic isn't being disabled" and when increasing the microphone boost that there is audio coming through the case.

Notice how I'm tapping the bezel on the laptop right where the microphone is and that the meter is showing green for input volume then how it "magically" stops when the cable is plugged in, this can be confirmed at the 16-17 second mark when there is a pause in the audio that they are NOT both active. Once again, the laptop mic is indeed disabled. When the mic boost is enabled, you can hear the tapping and scratching through the speaker but not the microphone as I tap the mic again with full mic boost/gain and no change to the meter.
 

eorange

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That is peculiar. Stretching here, but...you induce a mechanical shock on the scanner case; maybe those waves are absorbed by the speaker cone and inducing some sort of back current through a poorly designed section of the amplifier.
 

VynylScratch

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While I do agree with mechanical shock during the tapping, I don't think the scraping would be shock. I do agree that the waves are absorbed by the speaker because after I finished the video I had to check myself by talking loudly close to the speaker. It was coming through the laptop but not absurdly loud.

Both operate on the same principle of using sound pressure, either to vibrate the diaphragm, moving the coil as a microphone or powering the coil to produce sound pressure.

Weird, is it only this scanner that does that?
I'm going to try on my Pro-2096.
 

VynylScratch

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Same outcome, however along with scratching it would do it too if putting on the antenna, which makes me think it's definitely somewhat ground related.

Regardless, this post was just meant to be a tip for other feed providers that may have experienced the same type issue.
 

jonwienke

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Something is wrong with your scanner if the speaker isn't being disconnected when you plug in the cable going to the laptop. There's usually a mechanical switch built into the jack that does that. Maybe that switsh is shorted or something..
 

Ubbe

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If coils in a receiver isn't fixed properly they will vibrate with any mechanical movement. If that coil sits in an oscillator it will create FM modulation. Many receivers have problems that they are "microphonic" when you tap your finger on them. Modern receivers usually have SMD coils and will be almost immune to that problem. If you talk near the receiver and the voice managed to vibrate the components enough to create a noticable sound, then it must be a very bad problem where glue have come loose from a coil or other mechanical problems with components.

/Ubbe
 

KC7IMD

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My Radio Shack Pro-405 has this problem. When I first noticed it, I disconnected the speaker thinking it was acting like a microphone. That did not fix it. The radio is on a piano, and if you play the piano, the "music" can easily be heard on the scanner feed. I just moved the scanner and computer to the garage, and now it is next to a large stereo speaker, which, also can be heard on the feed if the music is loud enough. I think I will be taking apart the scanner again, and seeing if I can isolate the component that is causing the trouble. Crystals, coils, ceramic resonators all might be causing the problem. The radio is close to 10 years old now, I think. Wondering if a component has worn out or has failed. Fun stuff! Thank you VynylScratch for bringing this topic up again.
 

lehigh4me

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Thanks VynylScratch, I have been trying to figure out why I was getting the same thing going on with my scanner for a year lol. Tip works great!!
 

n0nhp

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Years of bench experience with two-way radios here....
Loose shields, bad grounds, some capacitors and coils in the audio line all can become "Microphonic".
Tracking down the culprit can take many hours. I have found a plastic spudger or the wooden handle of a cotton swab a good tapping source, don't use a pencil, the graphite tip is conductive and if you chip it or leave a mark on the board it can be a real problem.
Removing shields and cleaning the connections between them and ground can help as can a dollop of RTV around a capacitor or coil.

Use the record output of the scanner if possible to use a pre-amp audio level.

Potentiometers (volume controls) are another potential source of picking up audio from the environment.

I have seen some hacks that bridge the speaker jack so you can hear the scanner while feeding the audio to the computer.... DON'T DO IT! The loudspeaker is a low-impedance microphone and will directly couple audio to the output.

Bruce
 
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Ubbe

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I have seen some hacks that bridge the speaker jack so you can hear the scanner while feeding the audio to the computer.... DON'T DO IT! The loudspeaker is a low-impedance microphone and will directly couple audio to the output.
I wouldn't worry too much about that. The normal audio level that comes from the amplifier over a speaker are more than a thousand times stronger than the level that are produced when a speaker acts as a microphone. Also the amplifier are of a much lower impedance than the speaker and would short out almost all of the external audio signal.

Only time that "foreign" audio could come up to a level where it could be heard in a stream would be if there was an automatic audio gain controller in place with a 10.000:1 ratio without any noise gate function. It would in that case also produce a lot of hum and hash in the audio.
In none of the examples given where it the speakers fault as it was disconnected and still had "microphonic" problem in the streaming feed.

/Ubbe
 
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