The KD1JV SSB/CW QRP Transceiver uses a IRF530A MOSFET as its final power amplifier stage, to produce 5 W at 70% efficiency:
The signal comes through the gate, and the IRF530A operates in common source configuration, with drain impedance entirely through a toroid inductor.
How does this produce ...
hey I'm trying to setup serial communication with a network switch. it has 3.3v UART interface. Everything works fine with raspbery UART, but with every USB-TTL adapter I've tried (4 diferent chips) I cannot get RX working. TX works, I can send commands to the switch. Any idea?
@VolodymyrBoiko The adapters which you tried may have been expecting RX with 5V logic levels, and your network switch outputs 3.3V logic levels. RPi has a 3.3V logic levels.
https://www.waveshare.com/wiki/USB_TO_4CH_TTL https://www.waveshare.com/ft232-eval-board.htm pl2303 this one indeed was 5v CH340G with jumper set to 3.3
@VolodymyrBoiko Hm. I'm looking at this schematic at the second Waveshare link. If you set POWER JMP to 3.3V and remove the jumperfrom TXD JMP and RXD JMP, then you should be able to use the TXT and RXD pins on the FT232 PORT_1 connector.
@NickAlexeev That's how I've been trying to use it. Actually do not see TX/RX jumpers on the plane, only TxLed, RxLed. The situation was the same, I could send, but could not receive. Can it be related to difference in input impedance of these modules vs raspberry "mini-UART"? (sorry for my ignorance, I'm a total noob in electronics)
(this is the state of the jumpers, how I left it from the last time I tried)
@VolodymyrBoiko RXD and TXD jumppers are solder blobs. There are two separate pads and the lump of solder connects them together.
I suspect the RXD jumper. When RXD jumper is installed (the solder blob is there) the output of MAX232 is connected to the RXD pin and onward to the FT232RL. Then you connect the TX output from your network switch to the RXD pin. Now you have two outputs (MAX232 and your network switch) connected together. Which output is going to win? Nobody knows. Absence of communication is a norm in a situation like that. Let’s hope that one output haven’t fried the other.
[The MAX232 is a level converter from RS-232 to TTL logic level UART. The FT232RL is the bridge between logic level UART and USB (enumeration, drivers, and all that). ]
