Waveforms... Conditions for all below: Drive is from the HP 3325B at 2Fo, 5V square wave, 2.5V DC offset fed into amp driver board. Amp output through LPF into a quality dummy load (250W 50 ohm flan
Thanks Hugh and everyone else who commented and provided tips on my earlier post about this amplifier. I will wait for Jay to have a chance to comment but I *think* I'm OK on timing of the phase tran
Hello Paul, If my similar amp exhibits ringing on the drains (which I monitor in real time), it means an antenna mismatch or a dicky connection (PL type plugs were the cause, cheap junk off Ebay, a c
Hello Chris, There are plenty of possible causes here I think. When it comes right down to it, I'm not at all happy with the end result of my construction on this amp. If it ends up not working, it's
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
Paul I think you need to step back from this a little. One point, design/cable routing at 137kHz is normally not that critical and it is unlikely it is having much effect. Many us have ''haywired'' P
Hello N1BUG, Hello Paul, by way of comparison my home made PCB is attached right by the FET's by copper wire 90 degree angles, soldered to ground plane of PCB and ground plane of the main amp double
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
Hello Paul, typo in my last reply, the Teflon co-ax to the LPF is about twelve inches long!! Sorry. As Jay says, it's not the ringing per se, but if the ringing peak goes over the fairly low headroom
Hi Jay yes indeed but I think that the Vds(max) is quite high, and certainly not a prob at 12v, or even 28v. Alan -- Original Message -- From: <[email protected]> To: <[email protected]
Jay, I appreciate your help with this. See below. Forget that rather poor picture. Here are better ones. Overall view #1: http://www.n1bug.com/vd-amp1.jpg Overall view #2: http://www.n1bug.com/vd-amp
Yep, voltage breakdown of the FETs was my worry. However I may be making a false assumption. I assumed the voltage spikes in the ringing would vary linearly with applied drain voltage? Perhaps that i
I had to use the (carefully resonated and matched) antenna for this test rather than a dummy load but it appears the maximum voltage spike in the ringing does indeed vary almost linearly with applied
Hello again Paul What's the vertical board in the end of the case? If it's the multiplier I am not qualified to say what having in the same box as all that RF might be, but i would have some concerns
If it's the multiplier I am not qualified to say what having in the same box as all that RF might be, but i would have some concerns. FWIW, my own W1VD doubler for the 630m tx was squirly until mount
Hello again Chris, Yes that's what it is and yes that may be a problem. However at the moment for testing and troubleshooting elsewhere, I'm not using that board. There are no wires whatsoever connec
Ah I see what confused me.....I missed the first spike which is up to the top of the screen and not so obvious because of the shadow. That is high for 13v but the usual design criterial is to allows
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
I'm a bit late coming to this discussion, but that ringing looks exactly like that you get when there is too much leakage inductance in the transformer. It is common to see such waveforms in SMPSUs
