Aboutcleggsan Expertise All technical areas of Electronics Engineering.
Experience BSEE, MBA, Design, R&D, University Research.
Senior Life Member of IEEE. Life Fellow of AES.
Organizations IEEE, Consumer Electronics Society, Audio Engineering Society.
Broad teaching experience; work experience mostly in consumer electronics and conversion from analog to digital technologies. Pioneer in digital audio at all levels.
I need a squelch circuit to filter low volume levels (and some noise) out of a headset mounted in my motorcycle helmet. The source is a built-in head unit used for AM/FM/CB/Intercom and GPS. The only place I can tap in is the amplified auido out lines (or "speaker out") between the head unit and the headset. These are the equivelant of "speaker wires". I'm not an electrical engineer but if needed, can take simple voltage and current measurements. My problem is that there doesn't seem to be a commercial product that I can purchse. It appears the only way to get one is to build one. Do you know of anyone (maybe yourself) who would build such a circuit for me for a fair price?
Brad
Answer An audio squelch circuit is not rocket science and it would not be difficult to construct one. However, it has been my experience that to make one for actual usage on a long term basis, beautify it and package it so that it will fit and keep out rain and dirt, etc. as opposed to just making one for hobby demo - are two entirely different matters.
To make one by yourself or have someone build it for you will be rather much more involved than you might guess. I suspect that before you are through it will cost well over $100 plus labor.
The above is a Uniden CB radio with builtin squelch for around $60. You can find them on eBay for less. The idea would be to take your audio from the the unit you have and bridge it into the cb radio unit. You can then listen off the cb or run it back through your own unit.
There are several other motorcycle based units with squelch. Just google or bing for them. You would need the schematic diagram - or a good tech - in order to find the bridge in point, bring out a connector so you can feed directly. These units are small and can be mounted easily and don't draw much power in standby mode; less than 2 or 3 watts.
Hope this helps.
C
PS: One of the problems you will find it that with AM and FM when you lose signal you sometimes get rf or white noise that keeps the audio going because the squelch cannot differentiate between audio and noise. In most radio receiver circuits the squelch is part of the IF or carrier detection system and the actuation of the audio switch is a function of the channel carrier strength rather than the audio or noise level. So, depending on what you have in mind you may need to rethink how you want to apply the selective muting function.
