No transmissions from me this night. The little amplifier has died. I think it may be related to this resistance change in the antenna which is getting worse and worse. I'm going back to MF for this
when I visited Peter G3LDO used to see that dim glows under near darkness there was very dim arcing between windings or groups which you couldnt see clearly unless completely dark - slow changes over
Hi Markus, That is very interesting. It changes about 25 % during the first 2-3 minutes, then it seems to settle down and not change any more. It could be moisture somewhere, but any moisture here is
Paul Any chance one (or more) of the 3 high stack of cores in the transformer might have cracked? Might be interesting to hook a 50 ohm dummy load to the secondary of transformer, adjust turns ratio
Hi Jay, I wouldn't blame them for cracking in Maine. Sometimes I feel on the verge of cracking. ;-) I need to get an amp repaired and do some dummy load tests outside as you suggest. First just the f
Paul An old Heath Cantenna makes a good load. They're often seen at flea markets for short money. In a pinch, an electric hot water heater element (of appropriate voltage / current rating for 50 ohms
Hi Markus, Oh, you described it exactly! Just before the 'pop' of the fuse blowing I could smell something burning. When I opened the PA I could immediately see the nylon screw holding down the FET w
Hi Jay, I haven't been able to attend a flea market in years. I'm sure I can find a Cantenna on the auction site, but it won't be for little money. I've been thinking about an 800W flange resistor on
Hello Paul, Ooh it is a class-E PA? That explains much! They need a very accurate SWR to reach the high efficiency. Initially i've been a friend of class-E but what you see now is exactly the reason
Hello N1BUG, Paul, I have always shorted out any unused turns on the loading coil with no issues. The matching transformer has floating unused turns though, but I think it's similar to yours, again n
Hi Stefan, I understand and agree about Class-E, but this same PA was operating fine last winter with some very poor antenna conditions such as snow and ice changing the phase and resistance greatly.
Hi Paul, Am 24.11.2018 19:41, schrieb N1BUG: Third test: Moved dummy load to output of ferrite matching transformer with ratio set for 1:1 impedance, so minute RF carrier at 150W. At start, voltage a
Hi Stefan, Yes, it stayed cold. No. As before it was completely cold. Yes. The primary of the xfmr is connected between center and shield of coax, but not to antenna earth. The secondary of the xfmr
Am 24.11.2018 20:49, schrieb N1BUG: So what if I could make a dummy load with the same R as that of my antenna / earth and do the test again? Hmmmmm, this should not be necessary when the xfmr stays
Yes, I think it's not the xfmr. The other day I checked it immediately after a 15 minute TX period when the problem was occurring. During that 15 minute TX, there was quite a large change in the syst
So... I eliminated the shorted turn at the base of the big coil. Now any turns below the tap which goes to the "hot" side of the ferrite core impedance matching xfmr just float. Three things I notice
Hi Paul, An interesting story :-) Congrats to the latest improvements! Am 25.11.2018 20:08, schrieb N1BUG: 1. Loaded Q is much higher!!! Expected. 2. I had to move the tap further up the coil to reso
