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| RF filter from audiophool to realety. |
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| T3sl4co1l:
--- Quote from: FriedMule on May 14, 2018, 06:40:08 pm --- --- Quote from: rstofer on May 14, 2018, 03:58:51 pm ---I think T3sl4co1l's reply above about sums it up. If you can't measure it, it doesn't exist. --- End quote --- This is properly a truth with modifications:-) My scope can't measure 2.4 Ghz but that does not mean that mobile phones does not exists or that they can not effect electronic in some bad way, that a later scope can detect. --- End quote --- I covered that! Then you've been "picking up pops, buzz, spectral lines, etc. ... that's a start, if not necessarily a good one!" :) "Spooky action at a distance" is a hallmark of invisible, unmeasurable (with what instruments you happen to have at hand) RF. If it's varying with proximity (wave your hands over it, touch things -- assuming it's generally safe to touch), that's a classic sign. GSM phone beeping in amplified speakers is a painfully common example... however this is not usually introduced on power lines, because of the very high frequency. Tim |
| T3sl4co1l:
--- Quote from: FriedMule on May 14, 2018, 03:30:01 pm ---Would the power cords not act as antennas for every signal? I thought that a simple 100hz-3Ghz filter could be perfect for cleaning and then build it into a cast aluminium box? --- End quote --- This is neither possible nor practical, because the filter must exhibit its characteristic impedance near 100Hz, and 50Hz is much too close to this. The consequence: excessive series inductance, severely impairing output voltage under load, inrush current, voltage distortion, etc. On the upside, input power factor will be pretty good (harmonic current drawn by the load will be filtered out). You can make the characteristic impedance very low (so that load-side regulation is acceptable), but now you're drawing a lot of reactive power from the mains, which needs to be compensated out. You need huge, high quality inductors, and they're still going to get hot. Mains bandwidth (what's intended, and practical to carry on the network) extends to the low kHz, then becomes increasingly mushy beyond there (especially over distances). For this and the above reason, filtering below 1kHz is impractical, and may not even be desirable, but something cutting in the 10-100kHz range is quite practical, even common. But again, if you're just doing this for kicks, at the very least you're missing the elephant in the room -- the room itself. You need a shielded room to block ambient radiation. Much more practical to filter signals and power at the device level, and let the room and cables be noisy! Tim |
| FriedMule:
It is amazing all what I learn from you!! If we say that I would like to build an amplifier I understand that I can not (within reason) build a perfect filter but it is posible to filter a range of hz's i.e annoeng noise that comes from the room, radio, calling mobile and power cables. My knowlede are not good enough to decide the best action out from your great advices. The sollution of bying are probberly the best, but you know "it is fun to build it yourself", I just have to be sure that it is not dangerous and properly shielded! I would like to end up with (random order) a soft start, noisefilter, transformer and a audio circuit. What would you do and how (floobydust schematic 1, 2, 3 or other?), if you had to make a great filter for your own similar project? |
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