As part of investigation of radio remote options for the NanoVNA, hc01.com’s HC-12 modules looked promising. Some parts were purchased and tested for the application.
Above is a HC-12-USB and HC-12 using a Si4438 chip. Another of these and two HC-12 using Si4463 chip were purchased, however Si4438 were supplied against all orders.
The USB and a non-USB device were configured for 57600 DTE speed and 11dBm transmit power. Turns out there is a trap in programming these, the programming command input times out in less than 20ms between characters, and needed 100ms rest after each command.
In a test with the devices separated 5m, the maximum throughput was under 20kbps, just 30% of the DTE speed. The input buffer overran at about 220B. This is unusable for the NanoVNA application which has no flow control.
Testing did not progress to distance vs power checks and the inability to handle data at full DTE rate with a good signal made them unsuitable for the application.