For a point of reference for N1KO's observed 800 cycle
drift as his K2 warms up with use, I looked up the specs
for one of my non-TCXOd radios (IC-765) & overall the radio
can drift +/- 350 cycles from 0 to 50C & after 1 minute
from switch on, +/- 200 cycles in the first hour.
Bung in a 0.5 ppm TCXO & the 0-50C drift goes down
to +/- 100 cycles. Again, my 765 does not have one.
Unlike some other rigs also in use here, the 765 does
not use this reference to derive everything it needs inside
(the BFOs are simple crystal oscillators).
Both the 765 & my K2 with the all the drift mods were
tweaked on an HP5350B & then left to soak. The 5350B
is a relatively modern 20 Gc counter & after 30 minutes
from applying mains is in +/- 1 ppm range by itself, even
better with fitted option reference or external references
handy at the time (ultimately a R+S rubidium house
reference, model which escapes me now) - essentially
down to it's own +/- one least significant digit accuracy
spec. Drift observed was therefore essentially just that of
the radios.
I have yet to get the K2 to indicate the frequency it is
actually on (say <200 cycles) & stay that way based on
gut feeling from side-by-side operation of the two rigs over
a number of years of contesting.
And the 765's walkabout is glaringly obvious when
compared to a TS-950S without TXCO (but uses that
common reference for everything, I believe - can't find
manual at the moment). With the K2, there is roughly
+/- 500 cycle window that must be considered when near
band edges or trying to find some DX station somebody
else has spotted.
Depending on what one's operations are like, the
accuracy of the K2's frequency readout & amount of drift
observed may or may not be of concern. It is unrealistic
to expect performance in these areas like some radios,
as it was clearly not intended originally & with mods, is
still probably a bit shy of what might have been possible
if was a design goal - though it certainly beats any
"backpack" type radio I have had or used.
73, VR2BrettGraham
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