Based on a recommendation here sometime back, I bought a Symmetricom 58536A distribution amplifier so that up to four GPSDOs can share my rooftop Lucent 26db twist antenna. When I connect the antenna to its port on the 58536A, and a Trimble Thunderbolt to port 1, Heather shows no antenna connection on the Thunderbolt. By contrast, when I use the antenna and Thunderbolt (and/or another GPSDO) with a 2-port Instock PD5120 splitter/combiner, all devices function normally. The 58536A information note says it needs +4.5 to 13vdc. The antenna requires 3.3 to 5vdc. A multimeter measures +4.951vdc on the Thunderbolt's antenna port. If anyone has suggestions, I'll be very grateful. Frank

Does the setup with the PD5120 work if the TBolt is connected to either port? Some GPS receivers look to see if the antenna is drawing current, to determine if it’s alive. With a splitter, the receiver might not see an antenna current. I seem to recall the TBolt had a setting for that. KR > On Aug 17, 2020, at 3:04 PM, Frank O'Donnell <time@inkbox.net> wrote: > > Based on a recommendation here sometime back, I bought a Symmetricom 58536A distribution amplifier so that up to four GPSDOs can share my rooftop Lucent 26db twist antenna. > > When I connect the antenna to its port on the 58536A, and a Trimble Thunderbolt to port 1, Heather shows no antenna connection on the Thunderbolt. By contrast, when I use the antenna and Thunderbolt (and/or another GPSDO) with a 2-port Instock PD5120 splitter/combiner, all devices function normally. > > The 58536A information note says it needs +4.5 to 13vdc. The antenna requires 3.3 to 5vdc. A multimeter measures +4.951vdc on the Thunderbolt's antenna port. > > If anyone has suggestions, I'll be very grateful. > > Frank > > > _______________________________________________ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there.

Thanks much, Kevin, interesting point. If I connect the Tbolt to the PD5120's DC Block port, and another GPSDO to the DC Pass port, Heather shows the Tbolt's status with "Tracking satellites" in green. However, "Antenna open" continues to display in yellow. But it seems there was a more mundane explanation here. While moving cables around, I noticed that Heather's status display changed when I repositioned the cable between the splitter and the Tbolt. After replacing it with a fresh cable, the Tbolt is now working fine with the 58536A. If I can throw out another question, I'm not entirely clear on how the 58536A handles bias voltages from multiple receivers. There is a label with "DC Power" and an arrow next to each of its four receiver ports. The Symmetricom information note on the unit that I was able to find doesn't say anything at all about bias voltages. I've heard two conflicting statements from other users. One said the 58536A defaults to using only port 1 for bias voltage (unlikely to me, given the labels). Another said the 58536A combines any voltages present on any of the receiver ports and passes them on to the antenna, but blocks any from going back to any of the receivers (sounds more likely). Does anyone believe they have the last word on this? Thanks again, Frank On 8/17/20 4:22 PM, Kevin Rowett wrote: > Does the setup with the PD5120 work if the TBolt is connected to either port? > > Some GPS receivers look to see if the antenna is drawing current, to determine if it’s alive. With a splitter, the receiver might not see an antenna current. > > I seem to recall the TBolt had a setting for that. > > KR > > >> On Aug 17, 2020, at 3:04 PM, Frank O'Donnell <time@inkbox.net> wrote: >> >> Based on a recommendation here sometime back, I bought a Symmetricom 58536A distribution amplifier so that up to four GPSDOs can share my rooftop Lucent 26db twist antenna. >> >> When I connect the antenna to its port on the 58536A, and a Trimble Thunderbolt to port 1, Heather shows no antenna connection on the Thunderbolt. By contrast, when I use the antenna and Thunderbolt (and/or another GPSDO) with a 2-port Instock PD5120 splitter/combiner, all devices function normally. >> >> The 58536A information note says it needs +4.5 to 13vdc. The antenna requires 3.3 to 5vdc. A multimeter measures +4.951vdc on the Thunderbolt's antenna port. >> >> If anyone has suggestions, I'll be very grateful. >> >> Frank >>