This is such good content, really thorough, well prepared, technically correct, and answered all my questions. Using a cheap SDR as a spectrum monitor is so useful, I do the same with my SDRPlay RSP1A. Mine has a spectrum analyser client which is also useful. I would have been concerned about the furry bits around the tones, but you put it down to an artefact of the SDR. Pity this video doesn't have 2k views by now, but that's the way homebrew radio videos with real content seem to perform on YT these days. Keep up the great work!
Actually, the difference between AM and SSB signals on an oscilloscope is pretty clear, once you know what to look for: on an AM signal with sinusoidal modulation, both the positive and negative envelope shapes are each full sine waves, while on an SSB, the sine waves always cross through zero. So even though you can't see the phase, you can see that the two sides of the envelope are crossing over each other. And that's just at full modulation. On anything less than 100% modulation on AM, you will never see the positive and negative envelopes pinch together, while on SSB, regardless of the modulation drive, they will always pinch together, since they are actually intersecting.
@@Paul_VK3HN Hi Paul. Glad to see you online. I'm fine, thanks. I finished yet another QRP CW transceiver recently. I'm considering making a DC transceiver next, a clone of QCX. Never did it before. But I think I'm going to take a month or two of break from the homebrewing first. How are you doing?
@@R2AUK I've been good thanks, have also been taking a bit of a break from construction, still listening around when I can. I'll check out your videos to see your latest project. I've not built a phasing style receiver such as,QCX, that will be interesting. 73!
Using FR4 boards you can only expect up to 55dB carrier rejection which is the coupling through the board itself bypassing the mixer and filter input and output pins. You can improve carrier rejection but cutting a hole in the circuit board under the mixer and filter so there is air between input and output pins. Signal will still sneak around the edges, but air instead of circuit board will reduce carrier feedthru.
This is such good content, really thorough, well prepared, technically correct, and answered all my questions. Using a cheap SDR as a spectrum monitor is so useful, I do the same with my SDRPlay RSP1A. Mine has a spectrum analyser client which is also useful. I would have been concerned about the furry bits around the tones, but you put it down to an artefact of the SDR.
Pity this video doesn't have 2k views by now, but that's the way homebrew radio videos with real content seem to perform on YT these days. Keep up the great work!
Not my area of knowledge, but the videos are so well made and the content so interesting that I cannot help but watch!
great video, thanks for making it.
Actually, the difference between AM and SSB signals on an oscilloscope is pretty clear, once you know what to look for: on an AM signal with sinusoidal modulation, both the positive and negative envelope shapes are each full sine waves, while on an SSB, the sine waves always cross through zero. So even though you can't see the phase, you can see that the two sides of the envelope are crossing over each other. And that's just at full modulation. On anything less than 100% modulation on AM, you will never see the positive and negative envelopes pinch together, while on SSB, regardless of the modulation drive, they will always pinch together, since they are actually intersecting.
Great! 👍
Hi Alex, how are you going?
@@Paul_VK3HN Hi Paul. Glad to see you online. I'm fine, thanks. I finished yet another QRP CW transceiver recently. I'm considering making a DC transceiver next, a clone of QCX. Never did it before. But I think I'm going to take a month or two of break from the homebrewing first. How are you doing?
@@R2AUK I've been good thanks, have also been taking a bit of a break from construction, still listening around when I can. I'll check out your videos to see your latest project. I've not built a phasing style receiver such as,QCX, that will be interesting. 73!
Using FR4 boards you can only expect up to 55dB carrier rejection which is the coupling through the board itself bypassing the mixer and filter input and output pins. You can improve carrier rejection but cutting a hole in the circuit board under the mixer and filter so there is air between input and output pins. Signal will still sneak around the edges, but air instead of circuit board will reduce carrier feedthru.
That's a great tip. I may try that, it should be easy to clamp the board in my mini-mill and remove the copper in those areas.
This sounds like superstition and magick. I've seen plenty of mixers on FR4 that have better carrier modulation than that.