I purchased a used Siglent SDG2042X which is a 40MHz arbitrary waveform generator with bonus 200MHz frequency counter to replace my aging 25MHz arbitrary waveform generators. Test gear from Chinese manufacturers like Siglent and Rigol has steadily improved over the years and is now quite competitive. Despite my appreciation for the amazing quality of old HP/Agilent gear, in many cases, it makes more sense to buy something new from Siglent.
This generator works well and is feature-rich, but I was curious about an easy hack mentioned on eevblog (see The Siglent SDG2042X Thread) that describes how to upgrade it to 120MHz which turns it into the top of the SDG2K line: SDG2122X.
It turns out that the hack does indeed work and is easy to do; see results below. I don’t know if manufacturers intentionally leave these hacks available to make them attractive to hobby users while still selling the higher priced models to businesses who would be less prone to hack them, but either way, it’s much appreciated (and is a very nice signal generator)…thanks Siglent!
Note that the scope in the pic below is also easy to hack to 500MHz at 5Gs/s and moderately easy to hack to enable all optional functions.
The bonus frequency counter works quite nicely too, providing details like min/avg/max, sdev, duty, and frequency deviation in ppm relative to a reference frequency you specify. It needs about -10dBm (200mV) of signal at 200MHz, but lower levels at lower frequencies (e.g. it works at -20dBm ~= 63mV at 35MHz). Because the SDG2042X can be slaved to an external 10MHz standard, the generated frequencies and counter measurements can be very accurate; I usually keep it and other gear slaved to an external DOCXO standard.