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Hi guys, I received my 20m QCX Kit the other day. After reading all of the stories of people having low power out I was a little nervous that I would end up with one that was lacking near full power. What I don’t want to have to do if I could avoid it is start changing out parts that I had already soldered in place unless absolutely necessary.
After reading all of the information on the forum about people having low power issues I decided that to be on the safe side I would order replacement caps for C25, C26, C27 & C28 before I even started to build the kit. I felt it was a cheap insurance policy in case I received some of the caps that seem to be in question. Could the caps that I was going to order also be defective or out of tolerance? ? Sure, but more than likely not unless there was a really big run of sub par caps and with respect to tolerance, I could quickly measure them before I soldered them to the board.
So as I was building my kit I decided that I would wind L1-L4 and test them on my inductance meter. According to my meter which I trust very much each inductor required one less turn and fairly critical spacing on the windings to match the specified inductance. Once I had each one tested and tuned I carefully soldered them to the board.
I realize that tuning the inductor does not take into consideration the inductor’s counterpart in the circuit but I wanted to at least match the specified inductance as close as I could. Also keep in mind that the design typically doesn’t require this careful attention but with some people’s recent findings I wanted to give my 20m QCX every hope of not having any issues. I doubt that Hans wants us all to take the steps that I took because this issue seems to be very isolated but if you’re like me, I have far more patience during the build process than the troubleshooting process. If you read between the lines, I’m a better builder than a troubleshooter. My electronics degree is nearing 30 years old and while I use the basics of it everyday, component level troubleshooting and circuit design is not something that I’ve done much of in the last 20 years.
So after going throigh the setup process into a dummy load as I did a few weeks back when I built the 40m QCX, I put my power meter inline and took a deep breath. At 14.000 it’s 4.5w and at 14.150 it’s 4.95w. That nearly .5 watt difference between those two frequencies rises fairly quickly as you tune up the dial. On my antenna the difference in power output between the antenna and the dummy load s negligible.
So would I have had any problems if I used the supplied capacitors for C25-C28 and wound L1-L4 with the specified number of turns and soldered them in place? ?That’s hard to say because we’ll never know. The good news is that I don’t have any power output issues and that’s what I was trying to avoid.
If you are like me and you are more of a builder than a troubleshooter it may be worthwhile at least until they are sure the questionable capacitors have run their course to buy new caps before you start a 20m QCX, even if it’s for your own piece of mind.
Curt M.

The guy that lives on the other side of him said “you never want to buy gas when the tanker is there because that churns up the dirt in the undersground tank while they are filling it”.

Hi Bill, my theory wasn’t new versus old like buying a fresher loaf of bread, it was more about buying from a different source. I’m not one to believe that defective components, especially the same component runs ramped througout the world and in many cases the age of a component except in a few cases makes very little difference.
My thought was the being that this doesn’t seem to be a widespread issue even amoung the kits Hans is turning out, buying the caps from what more than likely will be a different source and a completely different production run probably not even made in the same factory should at least rule out the issues that other people were seeing if in fact the caps were part of the issue which is still questionable. $6 or whatever I paid won’t break me so regardless of if the ones shipped with my kit were suspect, in my mind it was money well spent.
I used to have a neighbor that would buy gasoline if he saw the tanker truck at the gas station because it was “better gas” than what was already in their tanks. ?Somehow the new gas magically separated itself from the existing gas and made its way through the pump and into his car leaving the old gas behind. The guy that lives on the other side of him said “you never want to buy gas when the tanker is there because that churns up the dirt in the undersground tank while they are filling it”. We all have different ways of rationalizing things. Hi Hi