Posted: 5/24/2017 2:15:51 PM EDT
I am not familiar with the little circle symbol around the wire at the top is that some sort of shield? Trying to hook an aviation headset up to an Icom A21. I did bread board this with a few modifications which seems to work, I had to modify it because the radio has a TS plug but the headset has a TRS plug. 
Thoughts? |
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http://i32.photobucket.com/albums/d7/Meathook65/schematic_zpsnx5tktya.jpg I am not familiar with the little circle symbol around the wire at the top is that some sort of shield? Trying to hook an aviation headset up to an Icom A21. I did bread board this with a few modifications which seems to work, I had to modify it because the radio has a TS plug but the headset has a TRS plug. http://i32.photobucket.com/albums/d7/Meathook65/a2021_zpsmzdhvjsq.jpg Thoughts? That likely refers to shielded wire... [General] aviation mikes have historically been designed to interface to a "carbon mike" radio input, with a level of around a volt or so. There is a bias voltage on the mike jack to facilitate a carbon mike or other type of 'amplified' microphones, to match the input. Should be a lot of info on the web re: the subject. You are trying to do the reverse, and it may be necessary to provide the aircraft mike [that are nowadays electret or dynamic] with a 'higher power' [possibly 10ma or more] bias voltage and then adjust/attenuate the output to an appropriate level for the radio. Modern military headsets -last I was involved, used dynamic mikes, and may now use electrets. Electrets almost always have an integrated preamp that requires a low power bias. Icom should have a mic input voltage spec. Do you have access to a scope? They are sooo inexpensive for fantastic performance -nowadays. |
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Yep, shielded wire should always be used for a microphone cord, condenser or dynamic. Its very common. On my drawings, I usually prefer to extent the lines to show a cord and draw a circle, connected to the shield on both "ends" of the cord if the shield is used for a signal. Important: The shield should only be connected to ground only on ONE END of the cable if the shield is used for shielding only, to prevent "grounding loops".
BTW, make sure to add a DC blocking capacitor (~ 0.1 uF) if you decide to connect a dynamic microphone to that radio. Icoms usually prefer to use electret (condenser) type microphones and provide a low value DC voltage on their microphone connectors. |
| For such a simple project this has been very frustrating. I get the whole thing put together working fine separately but when I plug my ANR headset in to both the speaker and the microphone it keys the mic. If I use a standard headset it works just fine. So now there is some incompatibility between the headset the radio and I that I have no clue how to resolve. |
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For such a simple project this has been very frustrating. I get the whole thing put together working fine separately but when I plug my ANR headset in to both the speaker and the microphone it keys the mic. If I use a standard headset it works just fine. So now there is some incompatibility between the headset the radio and I that I have no clue how to resolve. Why not post schematics of exactly what isn't working... And those an Icom microphone. |
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That sounds like a ground issue. Just guessing, but it sounds like maybe the icom radio has a Mike ground that is separate from the headset ground and your ANR aviation headset has the grounds being the same ground, I wish I could remember more details but I read about this when researching connection between a beofeng radio and a sound card. or something like that. |
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I think we have a winner!!! Actually I just checked this before checking back in here. ANR leads share a ground the passive headset does not. Quoted:
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That sounds like a ground issue. Just guessing, but it sounds like maybe the icom radio has a Mike ground that is separate from the headset ground and your ANR aviation headset has the grounds being the same ground, I wish I could remember more details but I read about this when researching connection between a beofeng radio and a sound card. or something like that. |
| Yeah definitely the ground is the issue. I will either work around it or buy another radio at some point. The radio was free so other than buying an extra battery I am not into it for much. The radio is almost the same as my old HTX202 it uses the same battery form factor. |