The displayed Frequency Error is computed as; the clock count form the desired 80M clocks, per 1 second pulse from a GPS. The percentage reflects; the direction, and magnitude of over a sample period. For this test the sample period is 6 hours.
Note: the resolution from the clock counter within the Propeller when compared to the GPS second pulse is 16Hz, this maybe a function of my particular GPS or the clock count function of the Prop. Regardless, the error is recorded as; ERROR/16.
After about 12 hours of data collection, the TCVCXO stats indicates about +6% X 16 cycles per 80M clock cycles, or an error of;
16 x .06 / 80M => 12 x 10^-9
or, 12 parts per billion
The intent is to install the Huff-n-Puff circuit and then note the same stats.
Is this necessary? No, . . but it is fun to see what frequency accuracy and stability can be obtained with simple hardware! :-)