So far, very good.
Not really.
All the above (before the cap multiplier) filter much of the RFI, but definitely not all of it.
Since RF propagates (also) by radiation, the RFI present before the cap multiplier will be transmitted to the entire circuit.
There are better solutions than cap multiplier. Probably the best solution is the Jung Super-Reg, when used with sense wires. It is so effective because of it has a very fast error amplifier, that goes well into the RF band. What it does, apart from very quiet voltage regulation, when sense wires are used - it 'irons' the RF present on the devices' supply rails (which include the return, or 'ground') - regardless of how that RF got there. It 'irons' the RF present because of the error amplifier cancels whatever isn't present on the reference voltage. However that implies that the Super-Reg would best be encased in its' own shield.
So, my suggestion is:
Common mode wide band filter;
R core or E-I core trafo with static screen between the primary and secondary;
Common mode wide band filter;
Fast rectifier;
Mains frquency filter;
Common mode RF filter;
Jung Super-Reg with sense wires, shielded;
Good earthing practice;
RFI immune case.
Makes me wonder, what's the power intake of an average GSM/UMTS tower nowadays ?
Bonsai,
If your secondary filter is a snubber that eradicates the oscillation that occurs in secondaties when the diodes switch off then I agree that your scheme is quite reasonable but l have found significant subjective improements can be had by also having some series impedance in the earh legs before they come together at the star earth point. 0.1-0.2R or better still a choke.
If your secondary filter is a snubber that eradicates the oscillation that occurs in secondaties when the diodes switch off then I agree that your scheme is quite reasonable but l have found significant subjective improements can be had by also having some series impedance in the earh legs before they come together at the star earth point. 0.1-0.2R or better still a choke.
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Best is a snubber on the secondary winding, followed by common mode RF dilter.
The radiation hazard signs around an tower should give anyone pause to think about how much energy is present near a Cell tower.
Common mode chokes can only do so much for the conducted common mode energy. A wond inductor only works up to a relatively modes frequency and then the shunt cap takes over. A ferrite looks like a resistor (maybe 200 to 300 Ohms at best) which won't do that much.
Your perfectly isolated shielded box may not react internally to a 1KW transmitter but the cables to the next box will pass lots of energy along. You can only deal with this as a system and minimize the "openings" that could let interference in.
Power line conducted energy seems to stop mostly around 30 MHz. None of the power line communications system go above that because the losses are too great to be useful. However the signals are strong enough to couple from cable to cable in the distribution box even with big magnetic breakers in the way.
Active filtering, especially with remote sensing above even 1 MHz strikes me as wishful thinking. To work you would need lots of gain and very little phase shift at those frequencies, right where the gain is dropping fast and the phase shift is increasing fast. I would think a well placed low inductance cap would work as well or better.
Most of the power fed into a tower ends up as heat, including that used for cooling the equipment. Given the short wavelengths now used, my guess is that the main immediate hazard is cooking eyeballs - the limited blood supply means that deposited energy tends to accumulate rather than get carried away.
In a typical house, almost all the RF energy comes from stuff in the house. If you stand at the base of a cell-phone tower using a phone then nearly all the energy in your head comes from your phone, not the tower. Hence people who want to ban towers near schools etc. should first stop using cellphones near schools and never ever allow their kids to take a phone to school. No phones means no demand for a tower.
In a typical house, almost all the RF energy comes from stuff in the house. If you stand at the base of a cell-phone tower using a phone then nearly all the energy in your head comes from your phone, not the tower. Hence people who want to ban towers near schools etc. should first stop using cellphones near schools and never ever allow their kids to take a phone to school. No phones means no demand for a tower.
When I tried common mode chokes I found that they were less effective that full differential choke regulation but I never tried 3 common mode chokes as you are suggesting. I'll bear this idea in mind for future experiementation. Three common chokes are probably still cheaper and definitely lighter that chunky EI differential chokes.
IEEE-1900 covers up to 100MHz. I have only seen limited design activity up to 75MHZ or so. TM surface waves have been demonstrated up to 20GHz, it's not the Hams concerned this time but radio astronomers!
Everyone, I do not really know EVERYTHING that might make the nearly 'perfect' audio design, BUT I do know that practice, study, and exchanging opinions with other designers has been very successful to give me awards of excellence from a number of reviewers, even though I do not personally advertise, and my BEST PRODUCTS were never advertised in the USA. Yet, they get awards from: 'Absolute Sound' top 100 products from 1973-2013, with anything that qualifies, from my personal effort, when I am trying my very best. Why should this be? It is because these products are considered 'something special' by independent reviewers. No, I don't know any of them as a friend or a close colleague. Often, they are quite distant to me, when we bump into each other at a CES or a hi fi show. AND I am not the only designer that is successful (obviously) For example, Charles Hansen and Nelson Pass are equally acknowledged in the same awards. How do we do it? We do it by competitively designing better and better products as we gain even more experience.
I know that people think that it is all about politics, but it is not, especially from my experience. Personally, I hate politics, and refuse to play with it, even when pushed in that direction, on occasion.
I know that people think that it is all about politics, but it is not, especially from my experience. Personally, I hate politics, and refuse to play with it, even when pushed in that direction, on occasion.
D.Self wrote an artcle on this issue. he injected freqs thru the power supply and measured increased audio distortion at the amp output. It isnt the freqs that get filtered but the onces that do not and get thru. Filters have a limited range of freq that they are affective.... above that freq, they get passed to the amp circuitry.
Very wide bandwidth amps need to pay close attention to the ingress of HF/RFI.
Thx-RNMarsh
Very wide bandwidth amps need to pay close attention to the ingress of HF/RFI.
Thx-RNMarsh
EE nonsense, but as long as you are satisfied with whatever you are doing, all is well.
Not before you would explain, for example, what good is doing using ultra fast rectifiers (and then adding (very useful) snubbers across). I'm sure your superior EE intuition will help in finding the right answer.
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