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Author Topic: HT mic levels vs. audio out of Adafruit Feather M0 Express  (Read 6848 times)
KB0AZJ
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Posts: 2




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« on: February 12, 2018, 12:17:00 PM »

I'm using an Adafruit Feather M0 Express to build a fox transmitter. The radio I'm testing with is an old Radio Shack HTX-202. I have the PTT circuitry working fine. However, I'm having issues with audio levels.  The microcontroller I'm using can play WAV files, and I can hear the output in headphones pretty well. But, when I connect that to the mic input of the transmitting radio, the audio on the receiving radio is extremely weak.  It's there and understandable, but just weak.

So, my question is about mic audio levels. On the HTX-202 in particular, but also on the "average" HT in general: what voltage levels are required on the mic input to get good audio quality transmitted by the radio?

It's also a strong possibility that I have a wiring issue and not a voltage-level issue. Electronics is not my area of expertise and I'm basically making this up as I go....

If anyone has done this -- built a fox transmitter with an Arduino-ish board -- please share how you did it! Thanks!!

-Farren
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K7RJB
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Posts: 41




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« Reply #1 on: March 09, 2018, 09:20:54 PM »

Can you use a USBLink, that may solve your issue?
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K7RJB
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Posts: 41




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« Reply #2 on: March 10, 2018, 08:15:10 AM »

http://www.g4ilo.com/usblink.html
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KG4RUL
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« Reply #3 on: March 10, 2018, 11:04:27 AM »

Any chance we could see a schematic of your wiring?
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VK4FFAB
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Posts: 470




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« Reply #4 on: April 03, 2018, 05:58:02 PM »

What are the impedance of each circuit? 8 ohm audio of the micro and 600ohm input on the radio? I am going to have a stab in the dark and say that might be a problem.
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