This is a very rough direct-entry frequency generator I threw together several years ago using an old telephone keypad, a cheapo 4-line LCD display, an Arduino Uno, and an SI5351 clock generator chip. There is no filtering as it was only intended to generate quick test signals to check for basic operation of RF/IF circuits and audio pickup circuits. Frequency is entered in Hertz using the number buttons, then loaded via the asterisk key (*). If the frequency is out of range (4KHz to 150MHz) it displays "Invalid, try again". The hash tag key (#) adds an extra signal that is either 1KHz above or below (or both if desired) the center frequency to simulate the LSB and USB of an AM signal. I don't have the documentation as the computer on which it was stored was stolen, and never recovered. Its not super difficult to build as far as wiring, and the coding is also fairly simple using Arduino libraries already in common use for the keypad, display, and clock gen chip. This thing has come in super handy many times to do quick good/bad tests of IF circuit operation.
