ESP32 Based SDR Transmitter - Part 1 Audio Input

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In this new series I will be building and testing a low power SDR SSB Transmitter.

The schematics for the transmit mixer (work in progress) are here:

The code is here: (just PTT for the moment - more to come)

Original video:

Link for determining electret current

0:00 Intro
1:21 I/Q based transmitter block diagram
2:54 Schematic walkthrough for Transmit mixer
6:35 Board populated with supply, ESP32 and ES8388
7:58 Phase Shift testing
10:06 Arduino software walkthrough
11:49 Adding a low pass filter in software and retesting
13:41 Walkthrough of microphone and connections
15:33 Microphone preamp circuit
16:44 Microphone preamp board
17:24 Preamp board populated
17:59 Testing the preamp board on the oscilloscope
19:47 Connecting the microphone/preamp to the transmit mixer
21:06 Looking at the 0/90 degree shifted audio from microphone to oscilloscope
22:33 Wrap up and next video description
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Great Video, Nice, Waiting For Complete Transceiver..

PutuDarmayasa
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great video, i look forward to the next one

khimbittle
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great explanation Ian, keep them coming 🎉🎉🎉🎉🎉🎉

joedoe
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IIRC the ESP32 processor is similar in "power" to the CortexM0+, so I would image that the dual core rp2040 processor (pico) should also be usable here.

KennethScharf
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Great amount of stuff to learn here - where did you pick up the EN8388 module? I only find the chips (probably clones) at the regular eastern suppliers...

andrethomas
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Nice vlog. Question why dont you reduce the audio sampling freq from 44k to say 8k so then you wont need a software low pass filter of 4kHz?.

bendunselman
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Nice work Ian. Do you know what the value of the Microphone PGA gain in Register 9 ADC Control 1 is. It can be set for +24dB, just curious why you needed a microphone preamp. If you mention in the video my apology. Thanks Video is awesome can't wait for the next. 73

rfdave
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