Synthesizer 2. 138MHz to 4.4GHz Frequency Synthesizer
A serial controllable synthesizer that will output any frequency between 138MHz to 4.4GHz. Built in Arduino Pro Mini + ADF4350
This little syntesizer is usefull as a Local Oscillator in down/upconverters or as a signal generator for VHF, UHF and Microwave frequencies.
The current firmware let you set the output frequency using serial commands, future firmware might expand on this so it can be controlled from a Windows GUI software.
It can be run from a USB port or you can solder in wires to supply it with either 3,3V or 5V.
It needs 140mA of current. (Solder point on board marked TP1 is for 5V and TP2 3.3V, pick the one that suits you)
The RF output has a power level of around 0dBm (1mw) over the entire frequency range give or take a dB or so . (See picture)
It has a stability of 2.5ppm (parts per million) when using the built-in TCXO 10MHz reference. If you need more precision or stability there is an input for a 10MHz frequency reference.
The frequency steps are about 1MHz at 4GHz and 150kHz at 138MHz.
The built in firmware lets you set the frequency using simple serial commands.
To set the frequency to 150MHz simply send the command SETFREQ 150000000 on the serial port. There is also support for sweeping between a start and stop frequency, for incrementing or decrementing the frequency. See Screenshots for more info on serial commands or issue the HELP command.
Future firmware might support Windows GUI software to set the frequency.
The Synth has place for an 8 pin pinheader so you can interface buttons, rotary encoders etc. on it for direct controll (pin header not included). See the Schema for pinout.
There is also two I2C connections compatible with Adafruit and Sparkfun boards using STEMMA QT / Qwiic connectors.
This can be used to interface many peripherals like displays, keypads, rotary encoders etc.
Using the USB port and the Arduino IDE you can upload your own software if you so choose.
The device is compatible with a Arduino Pro Mini 8MHz.
The firmware is open source and available on my GitHub.
Comes with two SMA connectors that needs to be soldered and a 1.8m USB cable for power and programing.