Radio Shack Pro-405 used for streaming is picking up ambient noise and vibration

[KC7IMD]

Hi all!
I have a Pro-405 that I am using to stream feeds to Radio Reference. It has been online for about nine years. I noticed the other day that the radio actually picks up ambient (room) noise if it is loud enough. Physically tapping on the scanner is easily heard on the audio feed I am broadcasting. If I yell into the speaker, I can hear that on my feed. It is faint, but present. I thought that the speaker was acting like a microphone, and took apart the unit to see if I could disable the speaker (more than the audio jack already does). What I learned was that I can completely remove the speaker, and I still have the same symptom. Something else in the circuit is picking up vibrations and transmitting them into my feed signal. Anyone else have this problem?

 

[K9DAK]

Yep! I have the same issue with the PRO-197 I use for my feed. Tapping on the desk, the scanner itself, our dogs barking, can all be heard on my feed. It's very faint though so I gave up on trying to fix it several years ago.

 

[swstow]

same issue here , i brought a external sound card fixed my issue ,

 

[KC7IMD]

Thanks for the response K9DAK. When I was putting the radio back together, I noticed that the radio has at least two crystals in it. I suspect that the mechanical tapping might be picked up by a crystal, causing grief. At least I know that I am not alone with this issue. It is almost like I have an "Alexa" in my room listening to me!

 

[CycleSycho]

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Is there room in the case for a strip of dense foam? Might help?


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[KC7IMD]

same issue here , i brought a external sound card fixed my issue ,

An external sound card for the radio or the computer? Please provide more detail. My audio is pulled from the headphone jack of the radio, and is connected to the microphone jack on the computer.

 

[KC7IMD]

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Is there room in the case for a strip of dense foam? Might help?


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Lots of room for foam, but... The radio is on top of a piano, and I suspect that if someone ever actually played "this dust collecting piece of furniture", we would get a lot of "noise" on the feed! Good thing no one is that musically inclined in our household.

 

[swstow]

i got a new mono aux cable and a external sound card for my laptop that i run my feed from the speaker plug on the scanner to the sound card plug in , the sound card plugs into you laptop or tower USB and then you plug your aux cable into the sound card ( this is the one i got ) this remove the computer mic picking up the extra sounds ,

 

[KC7IMD]

Oh - okay. My problem is different. The sound pick-up is on the radio itself. Something in the electronics is converting sound vibration into an electrical signal, which is then sent to the computer for streaming. It is very interesting. I am going to try and isolate the radio from vibration with some foam padding, and maybe glue the crystals to the circuit board. I have a feeling that it is a crystal that is sensitive to the vibration that is causing the trouble. But I think isolating the vibration is the best bet at this point.

 

[wtp]

tap everything with a pencil and listen then glue down the offender.
i did that with a radio or one of my kids...
i think it was a scanner that gave feedback at higher volumes but it stopped when i flexed the board.

 

[K9DAK]

Hmm, yeah, crystals can become microphonic... good call. Maybe this Sunday afternoon when it'll be cold and rainy here I'll pop the case off the '197 and hit the base of the crystals with some hot glue to stabilize them.

 

[krokus]

Crystal filters are known to become microphonic, which couples into the audio.

 

[VynylScratch]

I know I'm a bit late but check to see if "Microphone Boost" is set higher than +0.0 dB in the sound settings for your input device, I just had this on and at 28.5 dB or so with a windows reinstall after SSD failure and could hear vibrations through the feed.

 

[tvengr]

Remove the cover and tap all over the solder side of the circuit board with a non-metallic object to locate the most sensitive area. If a solder connection has failed and the lead of a component is loose, the vibration of the speaker can cause the scanner to be microphonic. If you are able to narrow down the noise to a certain area of the circuit board, resolder all of the connections in that area.