Re: QCX 40 - Need help with BPF alignment
Alan de G1FXB
Hi John,toggle quoted messageShow quoted text
Something to bear in-mind I'm doing this blind as I have not built a QCX,
people who have, need to correct my statements if wrong!
C1 seems OK.
TX Power OK.
Overall the peaks seem low, past discussions have indicated people report scaling factors of 8/9, but as you say its dependant on AF gain position for all but C1 alignment.
There is a voltage table at the end of the Assembly Manual, section 6.4
The measurements were made using the QCX inbuilt DVM which has a lower I/P impedance than most stand alone meters.
At first sight the table is a little strange because it doesn't start at IC1 but the order it is made, sets the basic requirements and then follows the signal path through the different circuits.
For sake of convenience it would be best to use the inbuilt, unless you have any concerns to its accuracy.
Oscilloscope trace & levels can be found on the https://www.qrp-labs.com/qcx/qcxtrouble.html troubleshooting web page. If you have access to a scope, through a friend if necessary.
A quick bit of background,
What version kit have you, Firmware revision?
The kit otherwise went together OK and raised no queries?
If possible a couple of photo's of top & bottom of the PCB just incase it's possible to spot something.
On 09/08/2018 21:26, jmcf2005@... wrote: