non-linear phase shift causes distortion of the waveform. The ideal is to have linear phase shift with frequency, so an allpass filter would be designed to linearize the phase shift of another filter.

The power frequency in the US is 60 Hz which is full wave rectified producing 120 Hz ripple. In Europe, the ripple would be 100 Hz.

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non-linear phase shift causes distortion of the waveform. The ideal is to have linear phase shift with frequency, so an allpass filter would be designed to linearize the phase shift of another filter. <-- so, what caused the non linear phase shift??

The power frequency in the US is 60 Hz which is full wave rectified producing 120 Hz ripple. In Europe, the ripple would be 100 Hz. <-- so the bandstop filter could be use to reduce the ripple in the output from power supply??

i am sorry for the incorrect grammar i used

thank you very much

 

what caused the non linear phase shift??

Pure inductance produces a 90 degree phase lag of current with respect to voltage. When there is resistance in series with the inductance (and
there is always some resistance in the real world), the phase angle varies with frequency. The phase angle depends on the ratio of inductive reactance and resistance. The resistance is fixed but the reactance varies according to the equation: Xl = 2* PI *F * L. The reactance (Xl) is a linear function of frequency but because it is at 90 degrees relative to the resistive component, the phase versus frequency is non-linear. The phase angle is 0 at zero frequency (if you can imagine phase at zero frequency!), 45 degrees at the frequency where Xl=R and 90 degrees at infinite frequency.

A similar argument holds for capacitance except the current in a capacitive circuit leads the voltage and the capacitive reactance has the equation: Xc = 1/(2*PI*F*C).

so the bandstop filter could be use to reduce the ripple in the output from power supply??

That could be done, but in practice a low pass filter is used to pass the DC and reject 120 Hz and all higher frequencies.

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I think this is getting a little carried away :lol:

We're only discussing interference on a cheap MW radio, I still don't think it's been confirmed WHERE the interference is entering? - mains, RF, or perhaps directly in the IF?.

There seems little point getting complicated about filters, when we don't even know where (or what) it might be used for.

The main complain (as I see it?) appears to be that an expensive radio is better than a cheap radio - personally I don't find that surprising?. I thing it's probably unlikely to be down to adding some magical filter, just that the overall design is going to be better right through.

I can't remember the last time I ever used an AM radio?, although I still have one of the best ever made, a Hacker RP35. For those of you who have never heard of Hacker, they made the BEST portable radios in the world! - bar none!. Unfortunately, people ceased to be prepared to pay for quality, and Hacker went bust :cry:

I bought mine second hand in 1971, it was the loudest portable radio you ever did hear :lol: it runs off 18V - two PP9's in series, and has a large elliptical speaker.

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