Sorry you are having problems with this.
My code is not supported by the PHSNA group, if anyone has problems it is probably best to contact me directly.
The version you are using is my latest VERY EXPERIMENTAL version. It adds capabilities that probably nobody
but me wants. I only posted it because it does have a much improved menu system. I have added a ReadMe
file that hopefully explains. I have both DDS-60 (AD-9851) and Si5351 hardware in my PHSNA, probably
nobody else would even want to do this! User edits to the experimental Arduino code are expected.
THE ANSWER TO YOUR PROBLEM is that you should not install an Si5351 library. I have taken the code from the library
(from Etherkit) and inserted it into the .ino file. The Si5351.h file I posted needs to be in the same folder with the
.ino file. Then it should compile correctly. I did this because I have been burned too many times by Arduino
library updates that have killed my old projects.