Garth,
That approach is not flawed. When you tune in any signal of a known
frequency (in either LSB or USB mode), when you have it tuned properly
(for audio), then the actual BFO frequency subtracted from the VFO
frequency will be exactly the carrier frequency of that station.
Once you have properly tuned in the station, enter the menu for CAL FCTR
and alternate the internal counter probe between TP1 and TP2 - then
adjust C22 until the frequency read at TP1 minus the frequency read at
TP3 is equal the frequency of the station. Since your chosen station is
on an frequency that ends in two zeros, you can ignore the high order
digits in the display and adjust C22 until the low order 4 digits are
equal. and save yourself the continual subtraction process (but double
check when you think you have it correct.
That is only half the job - since the K2 does not use the frequency of
the 4 MHz Reference directly for the dial reading.
You must follow the C22 adjustment with a run of CAL PLL followed by CAL
FIL. In CAL FIL, you must 'change' each BFO frequency. If it was
correctly aligned before, move it up one bit and move it back down to
the original setting. Do the whole process in one sitting so that the 4
MHz oscillator does not drift between the setting of C22 and the run of
CAL PLL and CAL FIL. The short term stability for the 4 MHz oscillator
is good, but the long term not so.
After you have done all that, your K2 should be on frequency - allow a
+/- 20 Hz error since that is the BFO DAC resolution limit. If it is
worse than that limit, repeat the entire procedure, going back to the
adjustment of C22.
If you need more detailed information on the process, look at the K2
Dial Calibration article on my website www.w3fpr.com.
73,
Don W3FPR
On 2/25/2015 3:50 PM, Gareth - M5KVK wrote:
I know this has been done to death on here, but I'm confused.
I'm following Wayne's procedure to calibrate the 4MHz oscillator. I'm using
Radio China International on 9600kHz. By comparing the Rx audio on the K2
with that received on another receiver, I see that the Dial f on the K2 is
9600.44kHz.
Now, according to Wayne's instructions, I adjust C22 whilst comparing TP1
and TP2.
Now,the audio pitch, and thus my subjective comparison of the correct
frequency, is being determined partly by the BFO frequency isn't it? So,
surely this approach is flawed?
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