Steve,
When you can receive WWV and WWVH at the same time, that is handy
because there is a tone both at 500 Hz and 600 Hz on each minute. WWV
and WWVH do not transmit the same tones at the same time.
Glad to hear that you are now up and running and are about as close as
you can expect.
Yes, the tuning of C22 must be done carefully, one little slip and you
have to do it again, the adjustment is a bit 'touchy', but persistence
pays off in the end.
Next time, you can do it much more quickly - I am usually successful in
one pass. It does take me 15 to 20 minutes, but 8 minutes of that time
is waiting for PLL to run to completion, so I take a break during that time.
73,
Don W3FPR
Steve Kallal wrote:
Don,
I finally got to within 10 to 15 Hz at 10 MHz now. I decided to use
MixW for the 500/600 Hz WWV tones. It works really well for that part
of the calibration.
I had misread your web site. You do endorse the N6KR method. I did
find the WWV Signal Format web page. Out here on the west coast, WWVH
also mixes into the MixW waterfall as a weaker trace when only one
tone is present from WWV.
I found the best tool for C22 tweaking is a small glasses repair kit
screw driver. My plastic tool could do the real fine adjustments due
to the tightness of C22. Of course the screw driver is removed before
taking readings.
The part that wasn't clear to me at first, was the need to redo CAL
PLL & CAL FIL after EACH C22 adjustment. I read so many comments on
the reflector archives that mentioned simply listening to WWV and
listen for zero beat. Obviously that is in the greater context of CAL
PLL & CAL FIL reruns.
There must to something electrical loose in my K2. I had the CAL FCTR
TP1 & TP2 values matching once & then they changed a few minutes later.
Using Spectrogram or MixW in LSB/USB modes easier than the CW spot
method I used. Somewhere I read the CW spot audio signal may not to
very accurate. Even though I am confident in my tone matching
abilities my ear.
Not sure if I could do it in the time it took you to write it up,
maybe 30 to 60 minutes for me! A video on YouTube would be real nice,
except K2 has given way to the K3 in popularity.
The bottom line: my calibration is twice as accurate (half the delta)
against WWV, than before, although in the opposite direction.
Thanks for your help!
73,
Steve N6VL
K2/100 #2289
Don Wilhelm wrote:
Steve,
Yes, the "4 MHz" reference may have to be set a few Hz different than
exactly 4.00000 MHz to calibrate the dial accurately.
The best method I know of is to feed the K2 audio into a computer
running Spectrogram. This method compensates out any difference
between 4 MHz and the actual required frequency for the reference -
one does not even need to be concerned about the reference frequency
with this method.
On the Spectrogram line display, set markers (pointers) for 500 and
600 Hz.
Now tune WWV in LSB (or USB if you prefer) - 10, or 15 MHz, either is
OK - 20MHz requires a bit of a difference in the VFO/BFO calculation
due the the sum of the oscillators rather than the difference.
When you look at the Spectral line display of the WWV transmission,
you will see the carrier (only if you are mistuned), and a
transmitted tone (wait until the do transmit a tone). The tone is
normally either 500 or 600 Hz, but there is a 440 Hz tone for one
minute each hour and there are some non-tone minutes. You can look
up the transmission format on the web and it will tell you which
minute is which tone - or you can just wait and watch the tones
alternate. The short tone transmitted for one second at the
beginning of each hour is always1000 Hz, so I move the cursor to 1000
Hz (read the frequency in the lower left box of the screen) and click
to place a crosshair at 1000 Hz too, it is a handy reference if WWV
is weak ir the other tones are not clear.
Now that you have the Spectrogram 'picture' of WWV and have
identified the relevant tones in the audio (the carrier, and one of
the transmitted tones), tune the VFO first listening until the voice
sounds rather clear - then you may see the carrier near zero Hz and
the tone near the 500 or 600 Hz marker that you have set. Tune the
VFO until the tone is lined up exactly with the marker. Wait until
the next tone minute to be certain you are tuned correctly and not
100 Hz off.
Enter CAL FCTR, then check to see if the tones are still lined up -
you can fine tune a bit if necessary, but when you have the VFO set
correctly (for the tones, not the dial reading - the dial reading
will not be correct - that is why you are going to all this
trouble). Do not move the VFO after this, you will next be adjusting
C22.
Now, you move the probe between TP1 and TP2 until the frequency
difference is exactly equal to the WWV transmitted frequency. Since
WWV transmitts on 0000.000 kHz boundaries, just look for the low
order digits to be the same at TP1 and TP2. If the digits are not
the same, adjust C22 a bit and see if the frequencies got closer.
Once C22 is adjusted correcctly, the low order digits of the BFO
(TP2) and the VFO (TP1) will match exactly, and you can declare that
C22 is now set exactly right - do not touch it again.
Now, switch to 40 meters and run CAL PLL followed by CAL FIL (change
each BFO setting even if it is correct - moving it up a bit and back
down to where it was constitutes a 'change' to the K2.
Once that has happened, you are done.
Tune WWV again as before and note the dial setting - you should find
it no more than 20 Hz off. The DAC limit of tuning varies with
frequency, but averages about 13 Hz, so 20 Hz is within the expected
practical tolerance limits.
It takes a LOT more time to write this than it does to do it - it is
easier to do than to say.
73,
Don W3FPR
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