All,
I have gotten my QDX to work very well on 40 meters.? I do not have an antenna for 30 or 80 meters that does not require a tuner and am not comfortable in using the output of the QDX to trigger the MFJ auto-tuner that is required for the Ultimax 100 random wire antenna that I do have for 30 and 80.? I was careful on the original testing of the QDX on completing the build yet somehow damaged the PA MOSFETs such that I had to replace them and ultimately IC5 (74ACT08) as well.? That effort is in another thread on the server.? 20 meters was not open when I did this latest on-air test.
The reason for this post is to let you know that a scan that does not center the FT8 frequency of the band is most likely caused by an issue with either the L12 or T2 windings.? In my case, it was an extra turn in the first 19 windings that was throwing off all of the bands.? I am still getting a strange scan for 20 meters, but have not tried it on the air to determine if it is an issue.
The other key is that you do need to adjust the Audio Gain to center the green bar showing the input level on the WSJT-X screen.? Too much gain and the bar will turn red and the gain (or the input of the PC) will need to be adjusted.? For me, this will be an iterative process as I use the rig.
Hopefully, a troubleshooting guide will be built as more information becomes available.? An example would be that since all of my scans were off, the most likely place to look would be the section that is common for all of the bands;? Either the first winding on L12 or T2. If only 40 and 80 meters were to have an issue, then look at the last two windings and so on.? Having the tool is a great help and smart on Hans's part to include it.
To sum up where I am at now is that the kit does perform well, but can be a challenge to build.? It is not for an inexperienced builder and could require some expensive test and rework gear if not already part of your shack.? I will be waiting for the version 2 boards to become more available than the 375 or so that Hans has mentioned he is building.? At that time I (we) will re-evaluate to include in our club build list.? The rev 2 board does address the SMD inductor replacement that is one of my current issues.? The other is the seeming sensitivity to avalanche failure that can force surface mount repairs.? By this, I am referring to replacing IC5 that I and others have had to do on the failure of the finals.
Above are my thoughts based on my experiences.? Feel free to use or disregard as you see fit.? I AM open to any feedback as that is how I learn.
73
Evan
AC9TU
