The receiver is a Kenwood TS-690S. I think the internal ref oscillator
is 4mhz. If I remember correctly, the guy I bought the radio from
paid a little extra to have the TCXO installed as opposed to the plain
vanilla oscillator in a can they normally ship with. When calibrating my
bench counters and AFG units I have been using beat notes against
the 15mhz WWV as there is no interfering signal near it and I receive
the 15mhz signal around S9 during the mid afternoon. I switch the receiver
to CW mode giving me a 700hz tone then zero beat against that tone
to calibrate my bench test gear. I do have a double oven military 10mhz
TCXO that is always on. The daily drift is about 1 cycle in ten seconds
or 1 part in 100,000,000. I could tweak the trimmer for less drift but
it is fine as is, close enough for what I need.