For other LO considerations:
https://zl2bkc.com/projects/zlpll/
I've all three... (DigiLO included)
Mike
On 5/14/2020 2:57 PM, Leffke, Zachary via AMSAT-BB wrote:
Following up on an earlier request from Ed...here is the QEX article on a GPS Disciplined VFO based on the Si5351
https://hamsci.org/sites/default/files/publications/2018_QEX_Downey_GPSDO_Si... (link will download a pdf).
There are a lot of example projects out there in terms of example Arduino code and libraries for controlling the Si5351, particularly if you google 'Si5351 WSPR transmitter'. I saw at least one post about some building a quadrature LO out of one as well (implying some ability to control phase relationship that I don't fully understand yet between the three outputs). 'etherkit' and some of the products on QRP labs (that use the etherkit software) are also useful search terms.
Also the adafruit breakout can be found here: https://www.adafruit.com/product/2045, approx. $8. The etherkit folks also make a breakout board: https://www.etherkit.com/rf-modules/si5351a-breakout-board.html ($10) which is the one used in the above link (though they are pretty interchangeable). The base part is something like $2 on digikey for the custom PCB enthusiasts.
Again, not a drop in replacement for something like the DigiLO (Though I did confirm the digiLO has specific switch settings that would produce Ifs at 2m or 70cm for a 1265-ish RF freq.....there are a couple options). The Si5351 goes up to 160 MHz for starters (not 6 GHz), is a square wave generator and produces lots of harmonics (filters!)........but it is cheap, simple to use, and that first link above shows how to make a pretty cheap, GPS disciplined signal generator.........There are other 'watch outs' about the base crystal frequency when using the higher frequencies....not sure exactly what the issue is, something about step size......but that's the fun of homebrew.....lots of threads to pull.
For the really adventurous that like messing with untested HW and SW, there is this: https://github.com/zleffke/kicad_wspr/tree/master/si5351_featherwing_v1/rev-, I'm attempting to get an Si5351 breakout into featherwing form factor (I like the adafruit feather microcontrollers, and I like that adafruit posts their EagleCAD files on github, making something like this fairly easy to produce). There is also this for more Arduino code related to the Si5351.... https://github.com/zleffke/arduino_wspr ...my attempts at custom Arduino code, obvious from the name, I'm messing with WSPR, but the base code for interfacing with the chip is in there as well as an example (I use the etherkit libraries, unmodified). For the last two links.....USER BEWARE....not sure if I actually know what I'm doing yet or not (though my breadboarded WSPR transmitter based on this chip appears to work just fine). Hihi
Hope this helps! Slight tangent from the core L-Band discussion, but relevant. -Zach, KJ4QLP