31-07-2025, 10:28 PM
(This post was last modified: 31-07-2025, 10:31 PM by Mike Watterson.)
(10-01-2025, 04:14 PM)PerdioPal Wrote: A really cheap sig gen can be built with an Arduino and a DDS card such as https://www.aliexpress.com/item/1005006221365470.html
Actually that's an empty PCB for about €1.50, or assembled for about €14. Strange UI on website. I have one, but never connected it to anything. Arduino is a not very nice form factor and a range of CPUs. I prefer a PIC18 series programmed with JAL on a piece of stripboard. Some have built in USB. Or you can use a Raspberry Pi, or a USB - GPIO board with a laptop.
A simple two transistor circuit (osc + buffer) is less time consuming to build, needs no programming and can use a cheap frequency counter as display. Much cheaper and easier than a DDS. You can get cheap DDS signal generators that use that IC that have an LCD display, dubious UI and no real attenuator.
You need an attenuator too, down to maybe -80dB. Fixed ones of 6, 12, 24, 48 could be switched in and out to give 0 to 90dB attenuation in 6 dB steps. Assume 50 Ohms impedance.
