10kHz to 225MHz VFO/sig gen from China - Page 1
Forum section: electronics / rf-microwave

author: 807
author_rank: Frequent Contributor
timestamp: November 27, 2022, 09:56:37 pm
content: 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-bfa619I 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

author: iMo
author_rank: Super Contributor
timestamp: November 28, 2022, 08:21:18 am
content: What is the difference between the original si5351 and the MS5351M clone?

author: 2N3055
author_rank: Super Contributor
timestamp: November 28, 2022, 08:42:39 am
content: Quote from: imo on November 28, 2022, 08:21:18 amMaybe of interest..https://www.qrp-labs.com/synth/ms5351m.html

author: 807
author_rank: Frequent Contributor
timestamp: November 28, 2022, 03:24:07 pm
content: Quote from: 2N3055 on November 28, 2022, 08:42:39 amYep. 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).

author: 807
author_rank: Frequent Contributor
timestamp: November 28, 2022, 03:37:15 pm
content: Would have liked to have done a full Youtube review, but my scope & spectrum analyser are not accessible at the moment.

author: fourfathom
author_rank: Super Contributor
timestamp: November 28, 2022, 04:07:42 pm
content: 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=107There are a series of related posts.