10kHz to 225MHz VFO/sig gen from China

[807]

After finally getting interested in Arduino, I saw this project for a 10kHz to 225MHz VFO/sig gen...

https://create.arduino.cc/projecthub/CesarSound/10khz-to-225mhz-vfo-rf-generator-with-si5351-version-2-bfa619

I noticed that the author mentions a ready-built unit from China. Even though I had all the parts neded to build my own, I thought I would buy this Chinese one out of interest to see how it performed. I was only interested in frequency accuracy, so used my Leo Bodnar GPSDO set to 10MHz, as an external reference for my Racal Dana 1991 frequency counter. Set it up so I could read down to 1mHz.

I was amazed at how accurate & stable the unit was. Over a 12 hour period set for 10MHz, the maximum drift was -137mHz to +343mHz. The drift wasn't linear, it did bounce around a bit, but I was still astounded by the accuracy. Don't know if the room temperature had any baring as I didn't monitor it.

I don't know if I was just extremely lucky, or whether the Chinese supplier actually took the time to compensate for the crystal offset in software?

The chipset was a CH340 USB to serial, Atmel M328P microcontroller, TP4056 Li-lon Battery Charger, MS5351M clock generator.

This is where I got mine:-

https://www.ebay.co.uk/itm/394029668274

[iMo]

What is the difference between the original si5351 and the MS5351M clone?

[2N3055]

What is the difference between the original si5351 and the MS5351M clone?

Maybe of interest..

https://www.qrp-labs.com/synth/ms5351m.html

[807]

What is the difference between the original si5351 and the MS5351M clone?

Maybe of interest..

https://www.qrp-labs.com/synth/ms5351m.html

Yep. It seems like it's a drop-in replacement for the si chip. Only difference I can see is that it draws slightly more current (around 8mA more).

[807]

Would have liked to have done a full Youtube review, but my scope & spectrum analyser are not accessible at the moment.

[fourfathom]

The stability of that unit depends entirely on the characteristics of the crystal oscillator used on that '5351 board.  The boards are indeed dirt-cheap from Chinese sources / Amazon, and reasonably cheap from Adafruit and others.  But the oscillators used are also cheap and have little if any temperature-compensation.  Still, the units are quite useful as-is and both the original '5351 and the second-sources are remarkable little chips.  I've used the the Si and the MS parts in a few designs, feeding the chip variously from a TCXO, OCXO or GPSDO.  In many cases you can get accurate uHz resolution at 10's of MHz, due to the 20-bit fractional dividers used for the PLL feedback and the clock output stages.  The output has more jitter / spurious than a good NCO/Sine/DtoA generator would give you, but it's still quite good due to the excellent delay-line jitter suppression stage at the outputs.

If you're curious, I've got some discussion of the Si5351 on my ham-radio / tech blog: http://wb6cxc.com/?p=107 There are a series of related posts.