Hans' experiments are designed to
demonstrate no failure and so do so.
I'm nowhere near so easily offended or anything, and I do very well know and understand exactly the bias tendency you mention. Nevertheless I think it might still be a little harsh.?
It was the same in my former Software Dev career as it is here. The very best types of problem reports are when there's a very clear definition of the problem and how to reproduce it. Whether hardware or firmware. Then I can reproduce it here and try and resolve it and re-test.?
I remember an Iambic keying problem early in the QCX days when two Israeli hams as I recall, provided me with the most concise description I've ever seen. Complete with oscilloscope traces, and a comparison with a real Curtis keyer chip, which is kind of the golden standard of Iambicism. It wasn't an easy problem to solve but it was very well defined and that made it 100x easier than it otherwise would have been.?
A more recent example, relating to QMX, was Gunnar's sudden supply voltage switch from 6 to 12V and again it's so well defined that I could set up a test jig, reproduce it, and find firmware improvements to largely mitigate it.?
Same when you go to the doctor. The more info you can provide the better chance the quack has of correctly diagnosing your condition and fixing it.?
But what we have here instead is a very nebulous problem. If indeed a problem at all. Some people with BS170 failures. Others use them for years without trouble (me included). Some talk about BS170 drain voltage and how bad SWRs of certain types could make the voltages, which find their way back through the filters and switches and output transformer to the BS170 drains and fry them. Specifically the high voltage case is important because it is very hard to protect against fast enough, whereas high current, if reasonably moderate, is a slower death by overheating and therefore in QMX it would be possible to act against it fast enough.
So far the only precisely defined scenarios are the open load and short load. This is why I tested them. Other recommendations largely boil down to twiddling LC matches on some uncool antenna etc. Which I can do but it isn't as well defined and likely to take more time, which is why I haven't got to it yet.?
I do sometimes wonder if I'm the only one here with a QDX and an average oscilloscope and an average skill to wield it... at the least the number of QDX + oscilloscope owners seems low in comparison to simulators... maybe I'm in the wrong business hi hi.?
The issue of the dI/dt inflicted spike caused by the sudden key-up of QDX is also interesting, and I can reproduce it and take scope shots of it... it kind of has a bearing on the other BS170 problems if we speculate that an already suffering transistor could be even more vulnerable to SWR problems. It's for such a short duration it isn't clear it's really a threat. Or a contributing factor...
Be clear also again, that this spike isn't an issue on QMX because of its envelope shaping.?
There seem so many unknowns. It's not a nice problem at all. It's not even clear if it's actually a real problem. The BS170 issue could simply be a straightforward matter of too much current in low impedance SWR mismatch situations causing overheating, for example. Throughout amateur radio history, damaging or blowing finals isn't totally an uncommon thing.?
73 Hans G0UPL
L
