Harmonic Notch filter

"Stretto"

** Why don't you just f*ck off ?

All you are doing is wasting our time with your bullshit and mindless TROLLING !!

** Yes.

** Not possible.

.... Phil

ot

tch

Look up "comb filter". They can be quite simple and are widely used. However, filtering "all" the harmonics is not a realistic goal. Also, there are problems with some potential applications. For example, many people have attempted to filter out mains interference and its harmonics from audio recordings with comb filters, but the results are often disappointing. Other problems are that if the fundamental frequency varies slightly the change is magnified in the higher harmonics and they may miss the filter notches unless a tracking filter is used. The passbands are not flat in the simple implementations and the phase response is "interesting".

John

Look up "comb filter". They can be quite simple and are widely used. However, filtering "all" the harmonics is not a realistic goal. Also, there are problems with some potential applications. For example, many people have attempted to filter out mains interference and its harmonics from audio recordings with comb filters, but the results are often disappointing. Other problems are that if the fundamental frequency varies slightly the change is magnified in the higher harmonics and they may miss the filter notches unless a tracking filter is used. The passbands are not flat in the simple implementations and the phase response is "interesting".

-----

Thanks, this was basically what I was interested in. The mains frequency is rather tightly controlled so why is it so difficult to filter out? 60hz is not a musical tone(inbetween A# and B) and one has about a hz or two to play with.

s

lay

The mains frequency is only tightly controlled in the long term - so that clocks based on mains-driven synchronous motors continue to keep good time.

In the short term, extra load on the generators slows down their rate of rotation, and load shedding raises the rate of rotation of the generators, which act a fly-wheels.

The underlying control loops feed more (or less) steam into the steam turnbines or more (or less)gas into the gas turbines driving the generators so the frequency comes back to normal pretty quickly.

If you were hooked up to a totally modern system, where all the power was generated as high-voltage DC and converted to 50/60Hz AC by loads of high current switches, this might not be true any more, but I think we have a few years to go before regular consumers encounter such a system.

-- Bill Sloman, Nijmegen

ot

tch

yes it may be possible if you include DSP and / or transmission line based filters.

Mark

A a boxcar integrator of exactly one period of the fundamental is the usual method, as used e.g. in DMMs. (DMMs often use 100 ms, since that's an integer multiple of the period of both 50 and 60 Hz.)

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal

Probably because from about 100 Hz up to probably over a KHx (Google Minnie Riperton) are in the range of the fundamental of the human voice.

300 Hz - 3 KHz has enough harmonics for an intelligible voice, but can sound "tinny". That's the BW in original telephone spec, and was VERY common in the days when I was hanging around with HAMs.

Cheers! Rich

It's not difficult to filter out in general, it's difficult to filter it and its harmonics out of a hi-fi audio signal without making the audio sound weird.

Hope This Helps! Rich

"Bill Sloman"

The mains frequency is only tightly controlled in the long term -

** Wrong.

.... Phil

ot

tch

Is it possible to design an apostrophe that automatically knows when it's not needed?

Is it possible to design an apostrophe that automatically knows when it's not needed?

** The comma above knew when it ws needed.

.... Phil

Is it possible to design an apostrophe that automatically knows when it's not needed?

--
Is it possible to design a non-idiotic person who thing's he doesn't know 
everything?

Okay. This tells us that you wish to be thought omniscient. Could you spare the time to tell us how tightly controlled the mains frequency is likely to be from one minute to the next, or from one second to the next?

This is a primarily a forum where experts on electronics advertise their expertise, but credible advertising does depend on demonstrating actual expertise, rather than merely claiming it. You wouldn't want to end up with a reputation like John Larkin's.

-- Bill Sloman, Nijmegen

Depends what you mean by tightly controlled. The frequency shifts measureably when for example at half time on cup final day everyone in the country switches on a 3kW kettle more or less simultaneously.

It is extremely tightly controlled over 24 hours and longer term for obvious reasons. But it is generally slower at times of peak daytime load and runs fast late at night to catch up. In the old days of synchronous mains drives on telescopes this used to annoy astronomers.

Regards, Martin Brown

--
Thing is???

Okay. This tells us that you wish to be thought omniscient.

** Nope.

It asks you to prove your pig ignorant, f****it assertion.

And that proof must be in the context of a typical ANALOGUE notch filter at

50 / 60 Hz.

Quote form the OP:

" The point here is to design a circuit not much more complicated than a normal notch filter. "

Say +/- 1% of the centre frequency over the 0C to 50C temp range.

To be very generous.

You have no hope - f*ck head.

... Phil

"Stretto"

** Why don't you " FUCK OFF ''

you TROLLING WOG PIG ???

Twenty seconds of googling brought up this:

Jeroen Belleman

The one confirmed by Martin Brown? Or here?

er at

What do you mean by "typical"? Since the figures from Twente show the short term excursions to be largely confined to the range between 49.9 and 50.1 Hz, a regular filter wouldn't be much worried until you got the Q up to around 1000. A typical twin-T filter with a sharp null at

50Hz would be more sensitive.

Where I come from, a twin-T filter is a "normal" notch filter - nothing else gives anything like as deep a notch with a few components, though it is a total pain in the behind to get it set up so the notch is at precisely the frequency you want.

As usual, Winfield Hill knows a better solution

-- Bill Sloman, Nijmegen