Timeline for Eliminating mains hum from frequency modulated RF LC oscillators
Current License: CC BY-SA 3.0
9 events
| when toggle format | what | by | license | comment | |
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| Dec 13, 2017 at 20:34 | comment | added | hidefromkgb | I`ve ordered the chokes, will test the circuit with them. WRT the noise, it is most likely frequency noise rather than the amplitude one. See the question update. | |
| Dec 12, 2017 at 6:15 | comment | added | D.A.S. | It works on my sim tinyurl.com/y7jbvh3f consider decoupling ground currents with CM choke (Ethernet Phy) on output to isolate hum. | |
| Dec 12, 2017 at 4:44 | comment | added | D.A.S. | Ok thanks. The above photos only show white noise with one a few dB lower than the other. So 50Hz hum gone now with ground plane "donut"? What needs to be fixed now? | |
| Dec 12, 2017 at 0:30 | comment | added | hidefromkgb | There must`ve been a misunderstanding. I did actually examine the 455 kHz IF at a carrier of 480 MHz and then of 514 MHz; the frequency changed after I added the EMI shield. I posted the result in my third question update: there is an IF spectrum from DC to 220 Hz, see the pictures (#1: i.sstatic.net/188et.png, #2: i.sstatic.net/zlxKv.png). WRT the Faraday shield, it only has 2 slots, which you can see on the picture I also added to the question. The resistance is below my multimeter range (0.1Ω to be precise). | |
| Dec 11, 2017 at 22:51 | comment | added | D.A.S. | How tight is your Faraday shield? for resistance and slots? | |
| Dec 11, 2017 at 22:42 | comment | added | D.A.S. | I can't believe you do not understand antenna aperture effect of signal/wavelength aperture ratio. Why are you looking for baseband 50Hz on the SDR when it is on the modulation. you could examine AC coupled DC or 50Hz IF bandwidth of carrier | |
| Dec 11, 2017 at 20:51 | comment | added | hidefromkgb | I`ve updated the post and added the spectrum, but I`m not sure if I made it correctly. Unfortunately, I made the new board before you posted the answer, will try to find some CM chokes and see if they help. | |
| Dec 11, 2017 at 4:56 | history | edited | D.A.S. | CC BY-SA 3.0 |
added 639 characters in body
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| Dec 11, 2017 at 4:49 | history | answered | D.A.S. | CC BY-SA 3.0 |
