YouKits TJ2B, Construction Manual

Page: 53 / 56

Calibrating DDS Unit
(Note: This frequency count displays in "kHz". 12000.000kHz = 12.000000MHz)
Now turn on the frequency counter, and warm-up the frequency counter for 20 minutes
(Different frequency counter has different warming-up time. Consult the instruction for the
correct warming-up time). Turn on TJ2B.
Let it run for 10 - 20 minutes for the clock to
stabilize.
Connect the red alligater clip to the center of the DDS output cable, the black alligater clip
to the ground (the cable bread). Press SETUP to enter DDS setup interface. For the
convenience of reading, IFS should be at the default value, i.e., "0". For KIT A the
frequency reading is the starting frequency of Band 1, i.e., 12000.000 (9000.000 +
3000.000). However, due to the tolerance of the 100MHz clock, the reading might not be
12000.000. It might be a liittle lower than that. When you move to higher bands, the
situation might be much worse. It is necessary to calibrate the clock so as to have a more
accurate DDS frequency output.
If you calibrate DDS clock with IFS "-1600", you have to substract "1.600kHz" from
12000.000. The reading is 11998.400 in this case
In this example, the reading is "11999.976", 24Hz lower than the required frequency (the
reading might be greater at higher band.), indicating the 100MHz crystal is around 200Hz
lower that the labeled frequency. Press TUNE to select 100Hz tuning rate, and rotate
TUNE counter-clockwise to decrease the clock value until the reading is 11999.996.
Now
let's handle the 4 Hz error.
Press TUNE to select 10Hz tuning rate, and rotate TUNE counter-clockwise to decrease
the clock value until the reading is 11999.999 or 12000.000.