Riccardo Okay on TX end problems. On RX end ... second spectrogram shows signal from K2ORS beacon depressing noise floor some dB. I will ask Warren if he can shut down for a night for our next attemp
Looking for Riccardo and Domenico EbNaut tonight. Unfortunately there are more frequent static crashes tonight than in the past week. Jay W1VD -- Original Message -- From: Domenico IZ7SLZ <iz7slz.dom
No chance for LF EbNaut reception last night due to tremendous static levels. A line of thunderstorms over east central US was the cause. Jay W1VD -- Original Message -- From: [email protected] <
Paul In addition to Ward's comments ... To be more consistent with the original design (to avoid the "I built it just like ... except" syndrome) move the driver board close to the FETs to shorten the
Paul Pressed for time so just a quick response. Notice the small 'bobble' (around 3 volts) on the gate waveform on the way up ... that's where the FET is turning on. Turn off is about the same level
Paul Sorry for slow reply. I agree with all of Chris's comments. I seem to recall you posted a link to a pix of your amplifier last week ... but it must already have been deleted here since I can't f
Alan The main concern about the ringing is that the positive extreme stays below the drain source breakdown voltage ... with some 'headroom'. Otherwise ... Jay W1VD Paul I think you need to step back
Paul Thanks for the photos and information. I was more interested in the superimposed gate waveforms than the drains, though. A pix of the LPF as well would be appreciated ... think there was one las
Paul One other quick observation ... the leads of the thick film snubber resistors that go to ground are rather long. It's probably not visible in the photo of mine, but the milled circuit board 'poc
Paul Maybe try some 14 or 16 gauge lamp cord ... it's pretty pliable and can be wound tight against the core. That's what I used in the 500 watt deck. Put a piece of wet paper towel around the insula
Paul Okay on 78 material. Wonder if you measured your snubber caps? Notice they're maroon color which would indicate they're old ... possibly used or an off brand? All new CDE mica caps have been yel
Paul Sangamo is a good brand ... so if they're NOS, and the correct value, the problem probably lies elsewhere. Is your secondary winding solid or stranded wire? I find solid #14 THHN better conforms
Paul Roger all. Now that you mentioned the scope probes ... to get an accurate view of the waveform I remove the long scope probe 'hook tip' and use just the remaining short pin as the probe. I also
Andy Good idea on the multifilar winding. A fair number of these amplifiers have been built ... none of which exhibit the severe ringing that this particular one does. We're currently 'clutching at s
Paul Here are some gate pix with Vdd off (Vdd supply not handy at the moment). www.w1vd.com/FETgate1.jpg www.w1vd.com/FETgate1.jpg Sorry pix quality isn't better. Notice dead zone between the two pha
Paul The 1000 pF caps I used are mylar ... suitable for timing applications. Ceramic caps, if that's what you're using (sounds like it might be since they're Kemet), have rather poor value tolerance,
Paul I just tried my earlier suggestion of doubling the value of the 'timing' capacitors to 2000 pF on the amplifier. As expected, the dead zone between the phases about doubled ... and is now signif
Paul The outputs of the 74F74 (measured at the 74F74) should be such that one phase turns off while the other turns on ... essentially on top of each other with no dead zone. These outputs are delaye
