Koolertron Upgraded 15MHz DDS Signal Generator Counter,High Precision Dual-Channel Arbitrary Waveform Function Generator Frequency Meter 200MSa/s (15MHz)

Edited review: regarding the duty, I realized that there was specifically a pulse wave which is affected, and that the square wave is not. This was confusing since duty is selectable for all waves, but it does work. I also took this into the lab today and compared it to lab quality generators. I’m creating very low voltage, low frequency signals on this thing (10 Hz at 0.1V) and attenuating it down to about 200uV. This thing is a beast and does that no problem, even slightly better than some of the lab grade equipment we have. Do your own tests, but for my purposes this exceeds my expectations. I still have not tried creating software defined arbitrary waves, but if that works reliably I’d give this 6 stars if it was possible.Original Review: I’m using this for very low frequency, low voltage stuff (10Hz @ 0.1V) and it does a pretty good and reliable job. So far the only thing that doesn’t work is the duty. Adjusting it still results in a fully symmetrical wave. I also haven’t tried uploading arbitrary waveforms yet, but watched a YouTube video that tracked down the required software and it seemed a bit annoying to set up. So far it’s been a productive instrument, but unfortunate that I didn’t get a feature I paid for.

The default oscillator inside of this is a YXC 50.000 XO (possibly a OT2ED8K5JI-111YXC-50M). This oscillator doesn't suck, but it only has 10-20 ppm of precision and lacks temperature compensation.On my unit, I replaced its default oscillator with a Jaunch TXCO (model: O 50,0-JT32CT-A-K-3,3-LF) which costs about $5 on DigiKey, and has 2.5ppm precision plus temperature compensation :)Following this, a subsequent recalibration adjustment to the 'Freq. Fine Tuning' option in the 'System Setup' menu has allowed me to get a stable and low-ish jitter signal regardless of output frequency.

I’m impressed by the capabilities of this signal generator. Not long ago, a device like this would have been prohibitively expensive. The unit is compact and lightweight yet performs exceptionally well, making it a great addition to any test bench. While I’m very satisfied with its functionality, there are a few design elements that could be refined.The display and menus, although in English, retain some stylistic influences from the original Chinese design. This has no impact on usability but may feel slightly unconventional to some users. Setting the operating frequency is straightforward, though the process is a bit unconventional—you select a specific decimal position and adjust the value with the control knob.One minor inconvenience is that while the unit offers plenty of memory slots for saving operational states, it always starts up with its default settings rather than remembering the last frequency and mode used. It would be much more user-friendly if it resumed the previous operational state upon powering on.That said, these quirks are minor and don’t detract from the unit’s overall performance. While it’s not reference-grade test equipment—understandable at this price point—it is an extremely capable and excellent value for general-purpose use.

I used my new oscilloscope to view the various output waveforms (sine, square, sawtooth etc.). They looked good on the scope, and the scope indicated that the peak-to-peak output voltage was the same as the level that I had set the generator up for. It looked to be right on the marks. You can see the digital-to-analog conversion steps in the waveform, but they were not excessive, and that is expected with a digitally synthesized generator. They were not a problem for what I needed, and will likely never be a problem for my purposes. If you will be using this to test harmonic distortion of a high-end audio amplifier, you should probably use a much more expensive generator that uses more data bits. Also, I was using a digital scope, so some of that waveform stepping (quantization) was due to the scope itself.I placed a 50 ohm load resistor across the output terminals, and the p-p voltage dropped to 1/2 of what it was without the resistor. This is just what should happen with a generator that has a 50 ohm output impedance. It is light-weight (feels almost like a cheap toy), which made it easy to carry to a job site. I simply needed to generate a consistent modulating tone for testing a piece of radio equipment. It served my purpose very well.

I bought this a few years ago, and it has been great. But it is so light. I fixed this by purchasing 3 metal square junction box covers from the hardware store and mounting two on the inside of the Generator shell and 1 on the outside (see the pic). I used 3/4" machine screws and washers/nuts to mount. Problem solved.

I checked modulated sine wane output to my Heath 40MHz oscilloscope and it’s clean, when it works. Mine does not turn on until I press the power button several times and it at times turns itself off while in use. Questionable quality control.