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Author Topic: Connecting multiple sources to mic input  (Read 7910 times)
KB9BPF
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Posts: 22




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« on: March 19, 2011, 02:22:46 AM »

Hello group,

I run a RemoteRig setup to operate my TS-2000 station remotely but I also use the station locally. Also, I've found that there are some computer control applications that require use of the mic input - using the CAT PTT command activates the mic audio input, not the back panel accessory jack audio input.

This means a lot of plugging and unplugging stuff, and it's easy to forget to reconnect the RemoteRig when finishing a session in the shack.

I found myself with some spare time and knocked out a little design project I've had rolling around in my head for a while which I'm calling a Microphone Multi-source interface. It's a little interface that allows up to three microphone sources to be connected at once to a transceiver.

Here's a brief description:
Three inputs:
- Local Mic. PTT on this takes priority and mutes audio from other inputs. Local Mic audio unmuted if neither other PTT active, enabling local VOX operation.
- RemoteRig. Activating this PTT will mute idle local mic audio, preventing pickup of shack noise.
- Aux (for use with computer or maybe a TM-D710 as Sky Command Transporter?) Activating this PTT will also mute idle local mic audio.

Other design features:
- Individual trim-pot level controls on each input and the output for level balancing, as well as test points for taking measurements.
- Four paralleled 3-conductor mini jacks for sharing Speaker Audio.
- Audio ground on pin 7 maintained separate from PTT ground on pin 8, with optional jumper block to connect them through a small RF choke.
- Speaker audio common maintained separate, with optional jumper block to connect it to audio common through a small RF choke.
- Power is drawn from the 8V present on the TS-2000 mic jack.

This project could easily be built on a breadboard, but I used ExpressPCB's free software to design double-sided PCBs. I've uploaded image files of the three schematic sheets and of the PC silkscreen to the files area of the RemoteRig group on Yahoo! http://groups.yahoo.com/group/remoterig/

Although the mic connector pinouts are laid out with the Kenwood round 8-pin mic connector used on the TS-2000 in mind, there's no reason why one could not adapt it to other mic pinouts or makes of radio.

73
Brad KB9BPF
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W5DQ
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Posts: 1209


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« Reply #1 on: April 08, 2011, 09:54:24 AM »

Bite the bullet and get a small audio mixer board with multiple mic inputs. The model you'll need isn't going to have to have a super wide response curve and shouldn't be that much if you shop around and should have most if not all of the features you mentioned. You can bring up one mic and drop out the others and tailor the audio to match your voice. Best of all unless you have lots of time and equiped with a decent shopful of tools to do fab work, it is already built and ready to roll. You'll probably have to do some custom cables and such to interface the mics but those also may be available if you want a total turn key system. Not near as fun as rolling your own but these days, unless you've got easy access to parts houses, the shipping cost of buying piece meal from various places can be a deal killer. I am a world class scourger (I think my wife likes prefers to call me a 'packrat') and I collect and canabalize electronics when and where I can find them. I have boxes and tray organizers full of pieces and parts that I'll probably never use but I live in a remote and since our local Radio Shack closed a couple of years ago, there is no ready access to parts. And in all that I have, I figure I would have to go out and buy alot of this level of project so I'd go shopping for a commercial unit.

I built a audio equalizer and mixer board setup in college as a lab project and if it were me, I'd just go buy one today and have fun operating.

73 and good luck in the project,

Gene
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Gene W5DQ
Ridgecrest, CA - DM15dp
www.radioroom.org
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