Re: [time-nuts] Terminators on empty outputs/connectors
Hi, On 05/24/2018 10:41 AM, Clay Autery wrote: > Putting in a hardware order... > > Question: Is it recommended to put terminators on all unused GPS Distro > amp ports? Output ports on GPSDO and NTP servers (10MHz and PPS). > > Thanks! > All GPS splittes I have looked at so far uses the Wilkinson power-splitter. It provides some isolations between the output ports, or rather, the ideal scenario has perfect isolation, the real world not so much naturally. If you consider a two-port splitter where you leave one end open, and ignoring the fact that the splitter math actually wants a 50 ohm load to perform correctly, there will be some leakage over to the next port and full leakage back to the source. Usually we can assume that the source direction wave gets dampen in the amplifier sitting there to compensate gain or for a passive one dampens in the cable back and forth as well as not getting a perfect reflection in the antenna source impedance. The direct leakage to the next port is likely to dominate. Regardless, this will behave as multipath for the GPS signal and just contribute to the multipath environment that the antenna already have. It's only when you have a really crap splitter that you need to be careful. For carrier phase measurements, you need to be more careful about signals, but mostly for stability of signals. So, for most cases, I don't bother on my splitters. I would only care if I would really try to get stable and accurate measures, but not because it would have much of an impact, but just because I don't want a simple to fix thing do me any harm. 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.
Re: [time-nuts] Terminators on empty outputs/connectors
As usual, the answer is "it depends." If the output is a single isolated output, then terminating load not required, but no harm providing. If the output is a multiple output, from a single driver, through a resistive or transformer splitter, then the level stability on all ports and the port to port isolation is dependent on the proper termination of all ports. So, if multiple 10 MHz or 1 pps outputs, terminations highly recommended. --- Graham == On Fri, May 25, 2018 at 10:21 AM, Dana Whitlow wrote: > I recommend putting terminators on unused ports, on general principles. > But I don't > think it would ordinarily be necessary to use big-bucks terms, unless the > distro amp is > really cheaply made. > > If you have access to a VNA, it would be interesting to measure the complex > transmission > coefficient from input to one of the output ports while experimenting with > variations of > the number and locations of terminations for the other output ports. If > you find that none > of such manipulations have any visible effect, then you can probably skip > using terms > on unused ports. I should mention that any such measurements should best > be performed > at roughly the intended operating RF power level. > > And for extra credit, report your findings to this discussion group. > > Dana > > > On Thu, May 24, 2018 at 3:41 AM, Clay Autery wrote: > > > Putting in a hardware order... > > > > Question: Is it recommended to put terminators on all unused GPS Distro > > amp ports? Output ports on GPSDO and NTP servers (10MHz and PPS). > > > > Thanks! > > > > -- > > __ > > Clay Autery > > MONTAC Enterprises > > (318) 518-1389 > > > > ___ > > time-nuts mailing list -- time-nuts@febo.com > > To unsubscribe, go to https://www.febo.com/cgi-bin/m > > ailman/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. > ___ 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.
Re: [time-nuts] Terminators on empty outputs/connectors
I recommend putting terminators on unused ports, on general principles. But I don't think it would ordinarily be necessary to use big-bucks terms, unless the distro amp is really cheaply made. If you have access to a VNA, it would be interesting to measure the complex transmission coefficient from input to one of the output ports while experimenting with variations of the number and locations of terminations for the other output ports. If you find that none of such manipulations have any visible effect, then you can probably skip using terms on unused ports. I should mention that any such measurements should best be performed at roughly the intended operating RF power level. And for extra credit, report your findings to this discussion group. Dana On Thu, May 24, 2018 at 3:41 AM, Clay Autery wrote: > Putting in a hardware order... > > Question: Is it recommended to put terminators on all unused GPS Distro > amp ports? Output ports on GPSDO and NTP servers (10MHz and PPS). > > Thanks! > > -- > __ > Clay Autery > MONTAC Enterprises > (318) 518-1389 > > ___ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/m > ailman/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.
[time-nuts] Terminators on empty outputs/connectors
Putting in a hardware order... Question: Is it recommended to put terminators on all unused GPS Distro amp ports? Output ports on GPSDO and NTP servers (10MHz and PPS). Thanks! -- __ Clay Autery MONTAC Enterprises (318) 518-1389 ___ 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.
