As I have detailed here in prior posts, I bought a used amp some 2 years or more ago. It is an Amp Supply LK-500ZC which runs a pair of venerable old 3-500 tubes and also has full break in capability. Well I got the amp for a reasonable price which included a pair of not-so-new 3-500 Chinese tubes of unknown pedigree and condition. I am running the amp on 115 VAC so the line voltage is kind of soft and I normally never try to get more than 500 watts out of this amp under almost any conditions. As happens with older tubes, the higher in frequency one goes the less power out and increase in grid current and plate current for that asked for 500 watts.
To make a long boring story shorter, last evening our daily CW Sked was late and propagation was poor. We have attempted skeds on 40 Meters only rarely and last evening was an exception to our normal practice on 14 Mhz or 18 Mhz. So 40 M it is then. Propagation stunk. I mean barely able to copy one another. ESP all the way through. I got off easy as Chuck has an amp that loafs along at 1500 out. Mine is a bit more puny. With these conditions and this lower band I asked my amp to do a little more. More being about 1 KW out. A teensy weensy 3 DB more.
As most that read here are aware, I run open wire feeders. As is the general case, a fixed non resonant antenna fed with OWL feeders will exhibit high voltage and high current at various places along the line, all of which move around with frequency and band changes. Well that 1 KW on 7024 Khz found the weak spot in my feed line and arced an insulator in half. It turned into a hell of a light show and of course, smelled up the shack a bit. I suppose I need to find some herculean binding posts or some other way to make a quick release attachment for my chokes. Enjoy the photo.
As it turns out no repairs are imminent as that burn opened up a natural gap that was hidden by some unnecessary plastic that used to hold those posts together. Just Kidding!
Here is the ionogram from Millstone Hill for the period near our sked hour.
Messy huh? Recall that MUF is approximately 2.5 times FOF2 so at 2.6 MHz. the MUF was approximately 6.5 MHz. Notice the little Sporadic E layer just above the X Axis at 2.2 MHz. Nasty stuff Es to those of us that use HF propagation regularly.
Thanks for reading my blog. Best, Chas W5PG