On 10/10/2012 01:09 PM, Bob Camp wrote:
Hi
…. and if we have to go to something more exotic than simple two pole filters
the group delay (and it's variation) has got to go up.
Yes and no.
As you add pole-pairs, their group delay contributions adds up. However,
as you add pole-pairs you also get a pair of zeros for the slopes
(typically located in 0 and infinity for band-pass response) and you can
back off considerably in Q values, and aim for maximum flat group delay
in the pass-band. See the difference between the amplifiers in the article.
At least some of the HP splitters have RF filters in them. The same is true of
GPS receivers. A receiver or splitter in the attic will have many of the same
group delay issues as an antenna. I know, who would put one in the attic. Just
how warm does that rack get as the air-conditioning cycles and the vents clog
up?
The filters do add up, true. But then one should also recall the cable
in the total, as covered by others.
Cheers,
Magnus
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