ESP32 Based SDR Transmitter - Part 1 Audio Input

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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