[time-nuts] To use or not to use transmission line splitters for GPS receivers

Magnus Danielson magnus at rubidium.dyndns.org
Wed Oct 10 21:05:44 UTC 2012


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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