One is much better to take the filter's delay in account rather than NOT USING a filter!!! i can hardly imagine a GPS receiver/antenna without any form of preselection, and, unfortunately, they're many of those filterless units on the market!
73 de Normand VE2UM Montreal, Qc. Canada --- John Ackermann N8UR <[EMAIL PROTECTED]> wrote: > I had a chance recently to look at the performance > of the two-port and > eight-port HP GPS antenna splitters on a super-duper > network analyzer. > Screenshots of the results are at > http://www.febo.com/time-freq/pages/gps-splitter. > > In short, the minimum delay (at the center of the > passband) from antenna > port to output port is around 15 nanoseconds for the > eight way unit, and > about 22 nanoseconds for the two way one. The delay > seems consistent on > all the ports, with less than 1 nanosecond > variation. > > However, there is also a hump in the delay near the > edges of the > passband, about 12 MHz above and below the center. > The delay at the > edges increases by perhaps 5 nanoseconds, though > depending on the port, > it's not always symmetrical. > > So, an interesting question for any of you *real* > GPS experts is what > effect a variation in group delay of the RF input > has on the timing > solution? Is the true "length" of the amp/splitter > some average of the > delay across the passband, or, given the spread > spectrum nature of the > signal, does it not really matter? In fact, is the > "length" of the > splitter even related to the measured group delay? > > This also raises the issue that any GPS antenna that > has RF filtering is > likely to have similar delays; I've never seen that > sort of data published. > > John > > _______________________________________________ > time-nuts mailing list > time-nuts@febo.com > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > ____________________________________________________________________________________ Get your own web address. Have a HUGE year through Yahoo! Small Business. http://smallbusiness.yahoo.com/domains/?p=BESTDEAL _______________________________________________ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts