Hi,

I've been recently going through a similar process. Designing a UHF
VCO for a hobby project, mainly as a self-education project. As in,
rather than buying the thing from Minicircuits or whoever and be done,
learn how to design and build one myself, so that I never have to buy
them. And to get them much cheaper... a few cents a piece, as long as
you don't mind the effort.

Anyway, when I couldn't get it quite right for a while, with tuning
range, harmonics, output power, etc, here's what I did: Build a
prototype, measure the frequency and output level. Try with a few
different tuning cap values in place where the varicap would be. Got a
proper RF simulation software*. Spice is probably not the best tool
for that. See if simulated oscillator frequencies match what was
really measured. I found out that after I included all parasitics
properly (eg. 0805 capacitor might have about 2nH inductance), and
also the PCB interconnections and the right transistor model, I get
almost exact match. A 1.4GHz frequency in the simulation, within a few
% off the real measured frequency. So now I know I got the simulation
right, and I can go ahead and experiment with different varicap types,
circuit topologies, etc... and I only get to the next PCB+soldering
iron exersize when the simulated performance is what I need. Saves
time.

* I realise that getting 'proper' RF simulation software can be tricky/
expensive...

-- Cheers,
3flp