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

[Bob Devries]

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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