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Harmonic Notch filter

S

Stretto

Jan 1, 1970
0
Is it possible to design a notch like filter that not only filters a
frequency but all it's harmonics? The point here is to design a circuit not
much more complicated than a normal notch filter and not n independent notch
filters, one for each harmonic.
 
P

Phil Allison

Jan 1, 1970
0
"Stretto" <[email protected]>

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

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

Is it possible to design a notch like filter that not only filters a
frequency but all it's harmonics?

** Yes.
The point here is to design a circuit not much more complicated than a
normal notch filter and not n independent notch filters, one for each
harmonic.


** Not possible.




..... Phil
 
P

Phil Allison

Jan 1, 1970
0
"Stretto"
Look up "comb filter". They can be quite simple and are widely used.


** They are nothing like simple.

Thanks, this was basically what I was interested in.


** Piss OFF you FUCKING TROLL !!!!!!!!!!!!!!

The mains frequency is rather tightly controlled so why is it so difficult
to filter out?


** That was not your question.

You TROLLING PIG
 
S

Stretto

Jan 1, 1970
0
"John Walliker" wrote in message

Is it possible to design a notch like filter that not only filters a
frequency but all it's harmonics? The point here is to design a circuit
not
much more complicated than a normal notch filter and not n independent
notch
filters, one for each harmonic.

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.
 
R

Rich Grise

Jan 1, 1970
0
John said:
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.

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
 
R

Rich Grise

Jan 1, 1970
0
Stretto said:
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.

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
 
R

Rich Grise

Jan 1, 1970
0
Phil said:
"Stretto"
** They are nothing like simple.
** Piss OFF you FUCKING TROLL !!!!!!!!!!!!!!
** That was not your question.
You TROLLING PIG

Uh-oh, Phil's having another episode.
 
P

Phil Allison

Jan 1, 1970
0
"Bill Sloman"

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


** Wrong.




..... Phil
 
P

Phil Allison

Jan 1, 1970
0
Is it possible to design a notch like filter that not only filters a
frequency but all it's harmonics? The point here is to design a circuit
not
much more complicated than a normal notch filter and not n independent
notch
filters, one for each harmonic.

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


** The comma above knew when it ws needed.


..... Phil
 
S

Stretto

Jan 1, 1970
0
wrote in message

Is it possible to design a notch like filter that not only filters a
frequency but all it's harmonics? The point here is to design a circuit
not
much more complicated than a normal notch filter and not n independent
notch
filters, one for each harmonic.

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

Martin Brown

Jan 1, 1970
0
"Bill Sloman"

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


** Wrong.

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
 
P

Phil Allison

Jan 1, 1970
0
Some said:
The mains frequency is only tightly controlled in the long term -

** Wrong.

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


** Nope.

It asks you to prove your pig ignorant, fuckwit 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 - **** head.



.... Phil
 
P

Phil Allison

Jan 1, 1970
0
"Stretto"


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

you TROLLING WOG PIG ???
 
J

Jeroen Belleman

Jan 1, 1970
0
Bill said:
"BillSloman"

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

** Wrong.

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?

[...]

Twenty seconds of googling brought up this:
<http://leapsecond.com/pages/mains/>

Jeroen Belleman
 
P

Phil Allison

Jan 1, 1970
0
Some said:
The mains frequency is only tightly controlled in the long term -

** Wrong.

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

** Nope.

It asks you to prove your pig ignorant, fuckwit 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 - **** head.



.... Phil
 
P

Phil Allison

Jan 1, 1970
0
"Bill Sloman"
"Phil Allison"

You asked me to prove my assertion - which I did,


** You links proved the exact opposite !!!!!!!!!!!!!!

" The frequency has so far rarely deviated more than 0.2 % from 50 Hz, i.e.
it was almost always between 49.9 and 50.1 Hz. "


- rather than arguing with any of the points I went to the trouble
of making you, just re-assert your original - ill-founded - claims and
throw in the extra additional - equally ill-founded - claim that I'm
lying.

** Course you are lying.

You tell lie after lie after lie.

Deliberately posting wrong and refusing to ever back down IS LYING.


..... Phil
 
M

Martin Brown

Jan 1, 1970
0
If astronomers had any brains, they would have used an electronic
motor drive that was crystal derived.

Astronomers have a *lot* more brains than you do!

Modern scopes are mostly servo controlled with shaft encoder feedback
under computer control these days - true even for high end amateur
scopes. This allows them to automatically slew to targets, correct for
the change in apparent motion with altitude and accept autoguiders.

Industrial stepper drives were used for a while in the late 70's, but
tended to cause unwanted structural vibration even with microstepping
compared to old synchronous clock motors driven from a sine wave.

But for a very long time cheap and ubiquitous synchronous clock motors
were the way to drive telescopes. A few customers even had Rolls Royce
cut large 359 tooth gears for the main drive so that their scope would
keep almost perfect sidereal time if the mains frequency was at exactly
50Hz. They were the ones that were most miffed about the higher and
variable mains frequency at night. This included an optical telescope by
Grubb Parsons that at one time in the 1960's was at Jodrell Bank.

It was definitely a step up from the governed clockwork drives that
preceded them and were very sensitive to balance and temperature.

Regards,
Martin Brown
 
R

Rich Grise

Jan 1, 1970
0
Michael said:
If astronomers had any brains, they would have used an electronic
motor drive that was crystal derived.
I once saw a telescope drive made from a clock movement, for some
reason, the balance wheel was exposed, so you could see it going
tick-tock...

Cheers!
Rich
 
N

Nico Coesel

Jan 1, 1970
0
George Herold said:
Hey the with a 'good' DDS function generator you can watch the mains
frequency move about. Set 'scope to trigger on the line and generator
for 60Hz square wave, (or 50 Hz on your side of the pond.) and then
tweak the freqeuncy to keep the display 'stationary'. You can see the
mains swing above and below the nominal frequency... fun.. if you've
got nothing better to do.

I think you are seeing the drift of the crystal which drives the DDS.
I once made a 0.5ppm DPLL to track public E1 clocks. Just blowing some
air at the board caused the frequency to change because of the
temperature change.
 
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