QCX Frequency Calibration


Erik
 

Hello all,
I just finished building my first 40m QCX.
The build was very fun and powered up great at first power. I setup WSPR and let it run for a few hours without any hits. I started to do some reading and troubleshooting and wondered if my frequency calibration wasn't a bit off. Reading the manual and searching the forums, I tried to calibrate the frequency using Menu 8.5. I am noticing that regardless of what I change this value to, the frequency on Menu 9.5 stays the same. For example, when setting Menu 9.6 to 6.000.000MHz and Menu 8.5 to 27.000.000 - 28.000.000, I always get a reading of 5.99821 on Menu 9.5. I have searched the forums and the Googles, but am lost.
Any ideas?

73 de Erik Morse
N9OJR


Alan G4ZFQ
 

, I tried to calibrate the frequency using Menu 8.5. I am noticing that regardless of what I change this value to, the frequency on Menu 9.5 stays the same.

Erik,

I'm not sure what 9.5, the frequency counter measures but it must be irrelevant.
9.6 is the generator so is also irrelevant.
8.5 is a software adjustment, no frequencies change EXCEPT the actual RF frequency.
Measure that, or check a properly calibrated WSPR waterfall.

73 Alan G4ZFQ


Al Holt
 

Since you have a 40m QCX you can use CHU on 7850 kHz for calibration if you're short of other test equipment. When you're 'spot on' the QCX will produce a 700 Hz tone. A smart phone with an audio spectrum analyzer app (usually free) can give you an idea how far off you are. Adjust and test; I'm never sure which way to go, but after a few trials you should get the hang of it. 

Once you're in the ballpark, transmitting WSPR, I'd suggest using K9AN, Steve Franke, for a frequency standard. He seems to cover most bands and his frequency reports are very accurate.

--Al
WD4AH


Guido ON6RL
 

Hello Eric,

 

Maybe you can try with smaller steps in menu 8.5.

Start again with 27.004 and move up or down in steps of 1 kHz, or even smaller and see what happens.

If you have the opportunity, check your QCX tx freq on another receiver.

 

73, Guido, ON6RL.

 

 

 

 

Van: QRPLabs@groups.io [mailto:QRPLabs@groups.io] Namens E
Verzonden: donderdag 6 september 2018 02:43
Aan: QRPLabs@groups.io
Onderwerp: [QRPLabs] QCX Frequency Calibration

 

Hello all,
I just finished building my first 40m QCX.
The build was very fun and powered up great at first power. I setup WSPR and let it run for a few hours without any hits. I started to do some reading and troubleshooting and wondered if my frequency calibration wasn't a bit off. Reading the manual and searching the forums, I tried to calibrate the frequency using Menu 8.5. I am noticing that regardless of what I change this value to, the frequency on Menu 9.5 stays the same. For example, when setting Menu 9.6 to 6.000.000MHz and Menu 8.5 to 27.000.000 - 28.000.000, I always get a reading of 5.99821 on Menu 9.5. I have searched the forums and the Googles, but am lost.
Any ideas?

73 de Erik Morse
N9OJR


Erik
 

Alan, 
Thank you for the reply.
Maybe I'm not understanding the process correctly, but through some reading I was under the impression that by utilizing the frequency generator, I am able to to align the output frequency of the radio via Menu 8.5.
Not having a reference radio setup to verify my QCX output frequency against, I am assuming that with the lack of WSPR contacts, my output frequency is off slightly.(I have a measured RF output of 4W with 12-13VDC)
I read that the process to align the final RF frequency was to use the signal generator (9.6) and then verify the output on (9.5). Depending on 9.5's output, you can adjust 8.5 to bring the output frequency in line with the generated frequency.
This procedure has been discussed before. What I am experiencing is no change in my output frequency based off corrections made to 8.5.
If this is not the correct way to "tune/calibrate" the radio for output frequency correctness, do you know where I can find information on how to perform this?

73 de Erik - N9OJR


Alan G4ZFQ
 

through some reading I was under the impression that by utilizing the frequency generator, I am able to to align the output frequency of the radio via Menu 8.5.
Erik,
Yes this is correct.
BUT you cannot use the CQX to check itself. The actual RF output, frequency counter and generator relies on the 8.5 setting. Change the setting on 8.5 and it all moves, the output changes but you do not see the result.
You must use some external standard or reference as described under section 8.5.
Or monitor your transmission on a WSPR receiver against other signals.

Or use GPS but be very careful if you do, keep your dummy load connected in case you do not read the instructions correctly.

73 Alan G4ZFQ


Erik
 

Thank you everyone for the replies and help! I was confused with the procedure.
I will try Al's advice using CHU since I do not have a reference radio hooked up at the moment.

Thanks again, OM's

73 de Erik - N9OJR


Rich
 

I would have thought the frequency counter would use the 20MHz crystal, so it would not be affected by changes to the 8.5 setting.

Rich


Alan G4ZFQ
 

I would have thought the frequency counter would use the 20MHz crystal, so it would not be affected by changes to the 8.5 setting.
Rich

Yes, I see from the manual that it does.
But it is still not possible to calibrate without an accurate outside reference, or counter.

(If Eric was using the correct connections and settings then it seems he should see some change using menu 9.5/6. I am suspicious that he was not measuring the generator output. It does not matter, these changes would have no significance regarding calibration.)

73 Alan G4ZFQ


Martin DK3UW
 

What about a CQ Call on the reverse beacon net.  http://reversebeacon.net/ They indicate your frequency.

Martin


Curt wb8yyy
 

Erik

the WSPR passband is narrow enough that it is easy to be out of it, and the PLL in the rig takes some time to calibrate even with the GPS attached.  Good idea to find your frequency in a CW transmission on RBN.  when you think you are close, try setting up frequencies at each end of the WSPR frequency span and possibly middle to see if you get any reports. 

73 Curt


N3MNT
 

Used the QRP Labs GPS module for calibration and per my Elecraft rcvr and RBN it is dead on.  I added a large sticker to the GPS board to remind me to always use a dummy load on radio.


Tony McUmber
 

Now that’s a tip I can use!  I tried it and found 3 spots on my 1st xmission; showed me +200hz or +300hz @7053, depending on the listening station report.  Not sure what I can do about it…

 

Tony N0BPA

 

 

From: QRPLabs@groups.io [mailto:QRPLabs@groups.io] On Behalf Of Martin Sellschopp
Sent: Tuesday, September 11, 2018 9:46 AM
To: QRPLabs@groups.io
Subject: Re: [QRPLabs] QCX Frequency Calibration

 

What about a CQ Call on the reverse beacon net.  http://reversebeacon.net/ They indicate your frequency.

Martin


Alan G4ZFQ
 

I tried it and found 3 spots on my 1^st xmission; showed me +200hz or +300hz @7053, depending on the listening station report.  Not sure what I can do about it…
Tony,

Apply reasoning. Mine is that menu 8.5 is the frequency at which the controller "thinks" the reference crystal is working.
Your very approximate check shows you are roughly 250Hz high at 7MHz.
Therefore the controller is being told your reference is lower than it actually is.
So you have to tell the controller that, raise the number in 8.5.
How much? 27MHz is approximately 5x 7MHz so raise the number by around 1250Hz.
With an accurate reference you could calculate more precisely.
I hope I got that right...

But you will not get it accurate until you find an accurate receiver or reference.
As mentioned before WSPR station K9AN is one who should be very accurate. Or see it you can find CHU or WWV.

73 Alan G4ZFQ


What about a CQ Call on the reverse beacon net. http://reversebeacon.net/ They indicate your frequency.


M0RON
 

How much? 27MHz is approximately 5x 7MHz so raise the number by around 1250Hz.

Surely 27mhz is almost 4x 7mhz, 5x 7mhz would be 35mhz, so should the change be 1khz?
Andy


Alan G4ZFQ
 

Surely 27mhz is almost 4x 7mhz, 5x 7mhz would be 35mhz, so should the change be 1khz?
Andy,

I did say "I hope I got that right..."
I did not:-) Maths was never my best subject.

73 Alan G4ZFQ


Tony McUmber
 

M0RON for the win!
I tweaked my ref osc up by 1khz. Now the spotters I see have my freq spot on or w/in 100hz at numerous frequencies. Lacking anything better, I may be able to live with that.
Thanks for the good info, Alan and M0!

Tony N0BPA

-----Original Message-----
From: QRPLabs@groups.io [mailto:QRPLabs@groups.io] On Behalf Of Alan G4ZFQ
Sent: Wednesday, September 12, 2018 11:11 AM
To: QRPLabs@groups.io
Subject: Re: [QRPLabs] QCX Frequency Calibration


Surely 27mhz is almost 4x 7mhz, 5x 7mhz would be 35mhz, so should the
change be 1khz?
Andy,

I did say "I hope I got that right..."
I did not:-) Maths was never my best subject.

73 Alan G4ZFQ