Qrpometer calibration


AG4CC
 

Thanks David,

Yes, I moved the shorted position on the back of the meter. 

i checked the diodes, and they are correctly oriented with the forward reading good. 

I also reheated the smt resistors a bit. 

There is still a nonzero power 0.71 with no RF applied. 

Anything else to check?
Karen


nm0s_qrp
 

Just for the sake of QRPoMeter builders, I have changed the calibration procedure in the past year, so that may be the source of confusion.  And the 4SQRP kits are different from the NM0S kits.

It is normal for the VSWR reading to be something besides zero with no RF applied.  But, the Power reading should be zero.  Check to see that the diodes are inserted in the correct orientation, and that they measure about 0.6v in the forward direction, using the diode checker in your multimeter.

Karen, did you move the decimal set solder short on the back of the meter?

David W. Cripe, NM0S
NM0S Electronics 


AG4CC
 

Thanks all,

i tried the calibration given by Glenn, but can’t get anywhere near 1.0, more on the order of 10-13. 

My kit actually has 3 test points. The 5v for 33 was fine. But the second step is to read the v at TP2 while applying 2 - 10 watts RF, derive the measured power, and then adjust the LCD to display that power. There is nothing in the instructions about TP3. Still not right, and response is not linear. 

I also note that when on, and no RF applied, the display has 0.65 for power and ~ 12 for VSWR. 

This is my first encounter with SMTs, and my next step will be re-flowing those. 


Karen AG4CC 


n4mj
 

My QRPometer doesn't seem to have a TP2, at least it isn't mentioned in the calibration instruction: 
Step 8 – Calibration There is one test point on the board, above the TX connector. This is labeled TP-1. Insert a fresh 9v battery into the battery clips, and flip the bottom switch up into the ON position. With a digital voltmeter, measure the voltage between this test point and ground. You may use one of the hardware mounting holes in the corners of the board as a ground point. Adjust the trim pot R33 until this voltage reads 5.00v. 

 Locate a QRP RF power source of 0.5W to 5W power level. Connect this to the TX connector, J1. Flip both switches into the up positions, so that the meter is ON and measuring VSWR. Apply 0.5W to 5W of RF power to the TX connector, and adjust the calibration pot on the back of the LCD meter until the display reads “1.00”. It is IMPORTANT to unkey the transmitter before turning off the QRPometer! The QRPometer is now calibrated! 


73 de n4mj//glenn


 
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On Thursday, February 25, 2021, 08:43:04 PM CST, AG4CC <telegraph@...> wrote:


Hi,

I recently completed this kit
adjustment of TP-1 to 5v is fine. But calculation of power from TP-2v gives 9.5w with KX3 set to 5w. Doesn’t seem right. I adjusted the display anyway, and it fluctuates between 8.5 and 9.5w. 

Any suggestions appreciated. 

73,
Karen AG4CC 


Johnny AC0BQ
 

Ge Karen 
The Qrp o meters have a history of needing a lot of heat on the load resistors.
Try cranking up the heat to high, then reflow them and let em soak.

It’s worth a try.
72
Johnny ACØBQ 

On Thu, Feb 25, 2021 at 8:43 PM AG4CC <telegraph@...> wrote:

Hi,

I recently completed this kit
adjustment of TP-1 to 5v is fine. But calculation of power from TP-2v gives 9.5w with KX3 set to 5w. Doesn’t seem right. I adjusted the display anyway, and it fluctuates between 8.5 and 9.5w. 

Any suggestions appreciated. 

73,
Karen AG4CC 

--
Check out the 4SQRP website at 4sqrp.com


n4mj
 

Might try a different QRP transmitter of known power level to verify the readings.  
73 de n4mj//glenn

 
PLEASE REMOVE all email addresses before you send it on and use BCC option when forwarding"
  Thank you! 



On Thursday, February 25, 2021, 08:43:04 PM CST, AG4CC <telegraph@...> wrote:


Hi,

I recently completed this kit
adjustment of TP-1 to 5v is fine. But calculation of power from TP-2v gives 9.5w with KX3 set to 5w. Doesn’t seem right. I adjusted the display anyway, and it fluctuates between 8.5 and 9.5w. 

Any suggestions appreciated. 

73,
Karen AG4CC 


AG4CC
 

Hi,

I recently completed this kit
adjustment of TP-1 to 5v is fine. But calculation of power from TP-2v gives 9.5w with KX3 set to 5w. Doesn’t seem right. I adjusted the display anyway, and it fluctuates between 8.5 and 9.5w. 

Any suggestions appreciated. 

73,
Karen AG4CC