Qrpometer calibration
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AG4CC
Hi, Any suggestions appreciated. 73,
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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, Any suggestions appreciated. 73,
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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:
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Check out the 4SQRP website at 4sqrp.com
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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 “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, Any suggestions appreciated. 73,
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AG4CC
Thanks all, 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.
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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
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AG4CC
Thanks David, 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.
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