Or you can use a second AM receiver and zero beat the tones. You can get
it very close that way.
On Mon, 28 Jun 2021, Don Wilhelm wrote:
Jerry,
Read the article on my website. Just adjusting C22 is not enough for a
complete job of dial calibration.
That oscillator is the clock for the MCU. The dial calibration data is
stored in EEPROM and is what is used to display the dial frequency. The
EEPROM is loaded by running the CAL PLL menu routine with the counter
probe in TP1.
Yes, C22 must be adjusted just before running CAL PLL or CAL BFO.
I use WWV which transmits 500 or 600 Hz tones on alternate minutes.
Using SSB, align those tones with the 500 and 600 Hz markers on your
audio spectrum analyzer to assure that you are tuned correctly.
Once you get the KSB2 option installed, you can enter the BFO
frequencies suggested in the manual and then proceed to do a more
precise dial and BFO calibration.
The DAC steps for the BFO limits the precision that you can achieve, but
10 to 20 Hz is achievable.
73,
Don W3FPR
On 6/28/2021 2:16 PM, jerry wrote:
Hi Don,
One of the first things I did after getting this rig in the mail,
was to verify that it received WWV at the proper frequency - and that
USB sounded like LSB. That reassured me
that the dial was accurate enough to keep me inside the ham bands.
People often instruct one to "zero beat" WWV. I fail to see how
this can be done with an SSB receiver with a properly set BFO, since
the carrier is then outside of the filter bandpass. Also, except
during the announcement period, WWV is actually transmitting multiple
"carrier" frequencies at the same time.
Not going to mess with SSB a lot at this time because I have the
SSB adapter on order, and I'd have to do it all again anyway after
receiving that.
I just calibrated the counter with the GPSDO. It was showing
9.....96 ( forget how many digits :). A quick tweak of the trimmer
cap got it to 10.0000 ( however many zeros ).
This is just a temporary bodge, because I also have a TCXO on
order, will have to do that again too.
- Jerry KF6VB
On 2021-06-28 10:39, Don Wilhelm wrote:
Jerry,
That GPSDO will be good for setting the dial calibration, but WWV is
better since it transmits AM at a fixed frequency.
Instructions for doing a good dial calibration are on my website
www.w3fpr.com. It explains the entire procedure.
Use SSB when doing the dial calibration because there is an offset if
you try to use CW - no offset with SSB.
73,
Don W3FPR
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