Tuesday, January 19, 2016

Arduino UNO, SI5351A breakout as 50MHz CW beacon

Been playing around with a $39USD Arduino Kit I bought from Amazon.com and an Etherkit Si5351A.  Total cost of this project was about $55 with shipping.

In the demo above the Si5351A is outputting 2mA or -7dBm or 0.1995 mWatts. http://www.cantwellengineering.com/calculator/convert/mA

The antenna I used is just a 6" long piece of wire.  Nothing major there.

The code for the Arduino came from here: https://github.com/la3pna/si5351_beacon

With a few tweeks (just text message sent, and some timing and removal of a 30 second carrier tone), I had it running in about 10 minutes.  Frequency is very stable, I bought the TCXO version of the Etherkit.  It could be improved most likely by removing the TCXO and replacing that with a GPSDO freq reference.  Which should lock it without an drift at all.

About 30 minutes after I shot this video the carrier really got stable.  With no drift or wobble.

This is running at -7dBm or 2mA for this demo or 0.1994 mW

SI5351A: https://www.etherkit.com/rf-modules/si5351a-breakout-board.html (I bought the $15 version with TCXO)

* All SMT components assembled, 0.1" headers included separately
* Fully tested
* Output frequency range: 8 kHz to 160 MHz (see Constraints below)
* Number of outputs: 3
* Output impedance: 50 Ω
* Output drive levels: 2 mA, 4 mA, 6 mA, 8 mA (into 50 Ω)
* Power supply: +3.3 V or +5 V
* Interface: I2C (on a 0.1" header)
* Output jacks: 0.1" header or optional SMA female end launch
* PCB material: high quality 1.6 mm double-sided FR4 with soldermask and ENIG coating
* PCB dimensions: 30 mm x 50 mm
* RoHS Compliant

Two multisynths cannot share a PLL with when both outputs are less than 1.024 MHz or greater than equal to 112.5 MHz. This means that you may only have two outputs under those conditions.