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Subject: Re: Building a simple video low pass filter
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Date: Sat, 11 Jan 2003 06:03:25 GMT
NNTP-Posting-Date: Sat, 11 Jan 2003 07:03:25 MET
> nonophil wrote:
>> I am trying to build a simple video low pass filter. My goal is to
>> reduce the output bandwidth of a digibox because my TV can't handle
>> sharp signal transitions without ringing artefacts.
>> The filter should cut frequencies > 5Mhz without creating an
>> impedance mismatch (digibox, cable and TV are 75 Ohms).
>> I used an interactive web-based L-C filter designer to mock-up a 3
>> poles 75 Ohms low pass filter
>> Would that work or am I missing something ? Any other ideas ?
> Unless youve got miles of cable between the digibox and the
> TV, I'd try something simpler.
> A capacitor on the end of the cable will act as a lowpass filter.
> Yes, it will screw up the impedance, but for a couple of meters of
> cable it's not an issue.
Actually the proposed filter will work well and will also "screw up" the
impedance (200R at 2.7MHz,0R at 6+MHz), but since both sides are terminated
(hopefully) the reflections will not have too much of an effect.
I found 0.82uH 470pF and 5.6uH to give a very good pulse response. But try
the 1capacitor solution first.
electronic hardware designer
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