On Oct 10, 2012, at 7:03 PM, Magnus Danielson <mag...@rubidium.dyndns.org> wrote:
> On 10/11/2012 12:03 AM, Bob Camp wrote: >> >> On Oct 10, 2012, at 5:05 PM, Magnus Danielson<mag...@rubidium.dyndns.org> >> wrote: >> >>> 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. >>> >> >> Unless you need to go to something with sharp skirts. Then you are likely to >> start from a fairly high Q lowpass prototype and add a delay equalizer. >> Starts to add up pretty fast... > > True. > > But we are talking about wise design for GPS antenna use. …. unless we suddenly need much steeper skirts due to a change in band allocations. > >>>> 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. >> >> indeed, but it's a bit tough to keep the cable all indoors. > > Indeed it is, which is why it may contribute significantly unless done with > care. I do know those that temperature stabilizes both the concrete pillar > and cable conduct. > > Cheers, > Magnus > > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
