Thanks Nikos.
I am following this up. I have tuned in the Russian 14.996MHz beacon: it peaks through my audio filter at 14.996680 as measured by my ears (ie 80Hz higher than expected).
I have never needed to check the accuracy of my audio filter (specified as 600Hz with 250Hz passband) as with my analogue rig it just works for my ears.? But I think I should do so for use with the uBITx.
73 Chris