[Coco] question to the hardware gurus (Gene?)

[Bob Devries]

oops! Replace the ? with the ohm symbol in my last post.
--
Regards, Bob Devries, Dalby, Queensland, Australia

Isaiah 50:4 The sovereign Lord has given me
the capacity to be his spokesman,
so that I know how to help the weary.

website: http://www.home.gil.com.au/~bdevasl
my blog: http://bdevries.invigorated.org/

----- Original Message ----- 
From: "Bob Devries" <bdevries at gil.com.au>
To: "CoCoList for Color Computer Enthusiasts" <coco at maltedmedia.com>
Sent: Wednesday, January 25, 2006 10:52 AM
Subject: Re: [Coco] question to the hardware gurus (Gene?)


> Torsten,
> From: http://cache.national.com/ds/LM/LM1881.pdf
> 
> When the source impedance is low, typically 75?, a 620?
> resistor in series with the source and a 510 pF capacitor to
> ground will form a low pass filter with a corner frequency of
> 500 kHz. This bandwidth is more than sufficient to pass the
> sync pulse portion of the waveform; however, any subcarrier
> content in the signal will be attenuated by almost 18 dB,
> effectively taking it below the comparator threshold.
> --
> Regards, Bob Devries, Dalby, Queensland, Australia
> 
> Isaiah 50:4 The sovereign Lord has given me
> the capacity to be his spokesman,
> so that I know how to help the weary.
> 
> website: http://www.home.gil.com.au/~bdevasl
> my blog: http://bdevries.invigorated.org/
> 
> ----- Original Message ----- 
> From: "Torsten Dittel" <Torsten at Dittel.info>
> To: <coco at maltedmedia.com>
> Sent: Wednesday, January 25, 2006 10:18 AM
> Subject: [Coco] question to the hardware gurus (Gene?)
> 
> 
>> Would someone have a look at
>> http://www.homecinemapage.de/sync.htm
>> Who can explain the funtion of the 620 ohm resitance R1 and the 560
>> picofarad capacitor in the second schematic? FBAS is composite video. It
>> looks like a low pass filter to me, could it be a color burst filter
>> (don't know the burst's frequency of PAL)? What if a replacement for the
>> LM1881 would have an integrated color burst filter, could I connect the
>> video signal directly to C1?
>> Same question for C3, what's its function concerning the power supply?
>> Removing HF noise from the IC's voltage?
>> THX,
>> Torsten
>>
>>
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> 
> 
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