http://www.to-way.com/tf/hp58516a.pdf

Hi I agree that in a normal system there likely will be no observable hit at all. That would be true with both the active splitter and with the passive splitter. My assumption was that in the absolute worst case, you have used up all of the antenna's gain with cable loss. It's only a useful case because that's where the splitter is likely to have it's maximum impact. It's likely a case where the receiver has given up already.... The basic question is still "what did I get for my money?". Bob -----Original Message----- From: time-nuts-bounces@febo.com [mailto:time-nuts-bounces@febo.com] On Behalf Of jmfranke Sent: Wednesday, January 27, 2010 12:59 PM To: 'Discussion of precise time and frequency measurement' Subject: Re: [time-nuts] HP 58516A GPS distribution amplifier information The noise figure hit may be nowhere as bad as 5dB because it depends on the noise figure and gain of the antenna preamplifier, not just the noise figure. John WA4WDL -------------------------------------------------- From: "Bob Camp" <lists@cq.nu> Sent: Wednesday, January 27, 2010 12:34 PM To: "'Discussion of precise time and frequency measurement'" <time-nuts@febo.com> Subject: Re: [time-nuts] HP 58516A GPS distribution amplifier information > Hi > > I'm sitting here looking at the spec sheet for the splitter: > > A normal four way splitter should have a loss of a bit over 6 db. > > The reason that's bad is that it may degrade the noise figure at your > otherwise perfect receiver (and sub 1 db noise figure antenna) by 6 db. > (it > may also do absolutely nothing bad at all) > > The splitter has a rated noise figure of 7 db max / 5 db typical. > > It has a gain that may be a loss of 3 db or a gain of 3 db. > > Worst case, it's got a -3db gain and a 7 db noise figure. It may degrade > the > noise figure at the receiver by 10 db. Best case it's got 3 db of gain and > a > 5 db noise figure. That's still a noise figure hit of 5 db. > > All of that is pretty easy to blow holes in as far as a real / normally > operating system is concerned. I *think* it's pretty close in the limit > case > though. > > If it is close, then the part (yes I bought one to) might improve things > by > 1 db. It also might degrade things by 4 db under the worst case conditions > where it likely matters. > > Am I missing something here? Obviously it does more than split. It may > have > better isolation than a conventional splitter. It also has the cute little > DC loads in it. > > Seems like a little bit more RF gain might have been a good idea. > > Bob > > > > -----Original Message----- > From: time-nuts-bounces@febo.com [mailto:time-nuts-bounces@febo.com] On > Behalf Of bg@lysator.liu.se > Sent: Wednesday, January 27, 2010 9:41 AM > To: Discussion of precise time and frequency measurement > Subject: Re: [time-nuts] HP 58516A GPS distribution amplifier information > > Hi, > > Another option is to remove the DC-block cap on port 1. Then let your > primary GPS power the splitter and upstream antenna. > > http://www.to-way.com/tf/hp58516a.pdf > > -- > > Björn > >> Hi >> >> I found a SMC-BNC adapter of the correct orientation in the bottom of my >> junk box. Somehow I doubt I'll ever use it for anything else. BNC cables >> and jacks are something I can find easily. >> >> The top of the unit is held on with screws so getting inside it should >> not >> be very hard. You could swap the SMC out to something that's more common >> for power distribution. Maybe an APC-7 ... >> >> My guess is they used the SMC because it's unusual. That way you don't >> get >> a cable with 30 VDC on it hooked where it shouldn't go. If you did run a >> 30 volt supply the dc could do some damage. Of course 30 volts on that >> unit connected to a "normal" antenna would do some damage as well. >> >> Bob >> >> >> On Jan 27, 2010, at 1:14 AM, SAIDJACK@aol.com wrote: >> >>> I recommend un-screwing that SMC since it is almost impossible to find >>> the >>> mate, and feeding two wires from a 5V supply into the unit through the >>> hole, and soldering the wires to the PCB. Works well for me. >>> >>> bye, >>> Said >>> >>> >>> In a message dated 1/26/2010 18:36:18 Pacific Standard Time, >>> bruce.griffiths@xtra.co.nz writes: >>> >>>> I'm using an HP 58516A GPS distribution amplifier to share my GPS >>>> antenna between my receivers. >>>> >>>> What is the proper part number or connector "name" for the power >>>> supply connector ? >>>> >>>> Thanks for your help ! >>>> >>>> Claude >>>> >>>> >>> According to the datasheet option 05 uses an SMC connector for the >>> power. >>> >>> Bruce >>> >>> >>> _______________________________________________ >>> 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. >> > > > > _______________________________________________ > 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. > _______________________________________________ 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.

 http://www.to-way.com/tf/hp58516a.pdf

Björn

  

The trouble with your worst case analysis is that most GPS timing receivers actually require a net gain from the antenna to the receiver or SVs wont be acquired or tracked. Bruce Bob Camp wrote: > Hi > > I agree that in a normal system there likely will be no observable hit at > all. That would be true with both the active splitter and with the passive > splitter. > > My assumption was that in the absolute worst case, you have used up all of > the antenna's gain with cable loss. It's only a useful case because that's > where the splitter is likely to have it's maximum impact. It's likely a case > where the receiver has given up already.... > > The basic question is still "what did I get for my money?". > > Bob > > -----Original Message----- > From: time-nuts-bounces@febo.com [mailto:time-nuts-bounces@febo.com] On > Behalf Of jmfranke > Sent: Wednesday, January 27, 2010 12:59 PM > To: 'Discussion of precise time and frequency measurement' > Subject: Re: [time-nuts] HP 58516A GPS distribution amplifier information > > The noise figure hit may be nowhere as bad as 5dB because it depends on the > noise figure and gain of the antenna preamplifier, not just the noise > figure. > > John WA4WDL > > -------------------------------------------------- > From: "Bob Camp"<lists@cq.nu> > Sent: Wednesday, January 27, 2010 12:34 PM > To: "'Discussion of precise time and frequency measurement'" > <time-nuts@febo.com> > Subject: Re: [time-nuts] HP 58516A GPS distribution amplifier information > > >> Hi >> >> I'm sitting here looking at the spec sheet for the splitter: >> >> A normal four way splitter should have a loss of a bit over 6 db. >> >> The reason that's bad is that it may degrade the noise figure at your >> otherwise perfect receiver (and sub 1 db noise figure antenna) by 6 db. >> (it >> may also do absolutely nothing bad at all) >> >> The splitter has a rated noise figure of 7 db max / 5 db typical. >> >> It has a gain that may be a loss of 3 db or a gain of 3 db. >> >> Worst case, it's got a -3db gain and a 7 db noise figure. It may degrade >> the >> noise figure at the receiver by 10 db. Best case it's got 3 db of gain and >> > >> a >> 5 db noise figure. That's still a noise figure hit of 5 db. >> >> All of that is pretty easy to blow holes in as far as a real / normally >> operating system is concerned. I *think* it's pretty close in the limit >> case >> though. >> >> If it is close, then the part (yes I bought one to) might improve things >> by >> 1 db. It also might degrade things by 4 db under the worst case conditions >> where it likely matters. >> >> Am I missing something here? Obviously it does more than split. It may >> have >> better isolation than a conventional splitter. It also has the cute little >> DC loads in it. >> >> Seems like a little bit more RF gain might have been a good idea. >> >> Bob >> >> >> >> -----Original Message----- >> From: time-nuts-bounces@febo.com [mailto:time-nuts-bounces@febo.com] On >> Behalf Of bg@lysator.liu.se >> Sent: Wednesday, January 27, 2010 9:41 AM >> To: Discussion of precise time and frequency measurement >> Subject: Re: [time-nuts] HP 58516A GPS distribution amplifier information >> >> Hi, >> >> Another option is to remove the DC-block cap on port 1. Then let your >> primary GPS power the splitter and upstream antenna. >> >> http://www.to-way.com/tf/hp58516a.pdf >> >> -- >> >> Björn >> >> >>> Hi >>> >>> I found a SMC-BNC adapter of the correct orientation in the bottom of my >>> junk box. Somehow I doubt I'll ever use it for anything else. BNC cables >>> and jacks are something I can find easily. >>> >>> The top of the unit is held on with screws so getting inside it should >>> not >>> be very hard. You could swap the SMC out to something that's more common >>> for power distribution. Maybe an APC-7 ... >>> >>> My guess is they used the SMC because it's unusual. That way you don't >>> get >>> a cable with 30 VDC on it hooked where it shouldn't go. If you did run a >>> 30 volt supply the dc could do some damage. Of course 30 volts on that >>> unit connected to a "normal" antenna would do some damage as well. >>> >>> Bob >>> >>> >>> On Jan 27, 2010, at 1:14 AM, SAIDJACK@aol.com wrote: >>> >>> >>>> I recommend un-screwing that SMC since it is almost impossible to find >>>> the >>>> mate, and feeding two wires from a 5V supply into the unit through the >>>> hole, and soldering the wires to the PCB. Works well for me. >>>> >>>> bye, >>>> Said >>>> >>>> >>>> In a message dated 1/26/2010 18:36:18 Pacific Standard Time, >>>> bruce.griffiths@xtra.co.nz writes: >>>> >>>> >>>>> I'm using an HP 58516A GPS distribution amplifier to share my GPS >>>>> antenna between my receivers. >>>>> >>>>> What is the proper part number or connector "name" for the power >>>>> supply connector ? >>>>> >>>>> Thanks for your help ! >>>>> >>>>> Claude >>>>> >>>>> >>>>> >>>> According to the datasheet option 05 uses an SMC connector for the >>>> power. >>>> >>>> Bruce >>>> >>>> >>>> _______________________________________________ >>>> 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. >>> >>> >> >> >> _______________________________________________ >> 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. >> >> > _______________________________________________ > 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. > >

Björn

Hi Bob, If you get a "smart" splitter they might have a "network" option or even as standard take DC for the antenna from any port on the splitter. This is from http://www.symmetricom.com/link.cfm?lid=4907 "The purpose of the micro-controller is to sense the bias voltage present on each of the output ports, and it always selects the lowest numbered port (1, 2, 3 or 4) to supply power to the splitter and to the GPS antenna. Each of the three remaining ports is configured by the micro-controller to sink a “standby” current of 25mA @5V." -- Björn > Hi > > I think the big issue with two receivers is if one of them powers down and > the other stays up. Then you try to back feed the one that's power down.