[time-nuts] Re: Trimble GSPDO - ISSUE
Hi there, thank you for all the information. I'm using a bullet antenna (don't remember the maker), on top of my office. Cable has 50ohm impedance (ultraflex 7) and average quality N connectors. Patch from splitter to receiver is 50ohm as well, but still using RG58, will upgrade it asap. Update on my issue: Yesterday I made some testing, removing the splitter and nothing changed (apart the samsung complaining about signal loss :) ). I removed the trimble board from its case, I gave a look to it and powered up again: well... may be a kind of magic but it works. Now the status led is blinking fast and this is the output I get from commands: UCCM >STATus - UCCM Slot STATE- 1-1. #Now ACTIVE STATUS [Master Manual] 1-2. #Before ACTIVE STATUS - [OCXO Warm] 2-1. #Reference Clock Operation [Not Used] 2-2. #Current Reference Type --- [GPS] 2-3. #Current Select Reference - [GPS 1PPS] 2-4. #Current Reference Status - [Good Accuracy & Stable] #GPS STATUS --- [Available] #Priority Level --- [LINK > GPS] #ALARM STATUS #H/W FAIL [ LINK ] #OPERATION ALARM -- [Antenna] 3-1. #PLL STATUS --- [ENABLE] 3-2. #Current PLL MODE - [OFFSET OBSERVATION MODE] UCCM >SYSTem:STATus? --- 57964-15 serial number 86854165 firmware ver 3.0.0.11-01LINK mode --- Reference Status __ Reference Outputs ___ XX Ref 8KHz 0: [LOS] XX Ref 8KHz 1: [LOS] TFOM 3FFOM 1 XX Ref 8KHz 2: [LOS] UCCM A Status[ACTIVE] XX Ref 8KHz 3: [LOS] >> GPS: [phase:-4.8E-06, settling] ACQUISITION ...[GPS 1PPS Valid] Tracking: 10 ___ Not Tracking: 0 Time PRN El Az C/N PRN El AzGPS 07:35:47 29 Jul 2021 26 73 268 45 31 22 215 37 ANT DLY 0 ns 16 45 309 42 Position 10 11 170 38 MODE Hold 29 32 77 43 25 6 141 34 LAT N 43:35:11.808 18 79 73 45 LON E 13:31:1.216 5 18 45 39 HGT +228.84 m (MSL) 23 31 143 42 27 19 281 40 UCCM >posstatus - 07/29/2021 07:36:06 - Position: LAT(N 43:35:11.808) LON(E 13:31:1.216) H( +228.84 m MSL) - Geometry: PDOP(0.0) HDOP(0.0) VDOP(0.0) num of visible sats > 10 num of sats tracked > 10 Receiver Channel State CH 0 > SateID(26) TrackMode(pos avail) SigValue(46) CH 1 > SateID(31) TrackMode(pos avail) SigValue(36) CH 2 > SateID(16) TrackMode(pos avail) SigValue(42) CH 3 > SateID(10) TrackMode(pos avail) SigValue(37) CH 4 > SateID(29) TrackMode(pos avail) SigValue(42) CH 5 > SateID(25) TrackMode(pos avail) SigValue(36) CH 6 > SateID(18) TrackMode(pos avail) SigValue(45) CH 7 > SateID(05) TrackMode(pos avail) SigValue(40) CH 8 > SateID(23) TrackMode(pos avail) SigValue(43) CH 9 > SateID(27) TrackMode(pos avail) SigValue(38) CH 10 > SateID(00) TrackMode(tracking ) SigValue( 0) CH 11 > SateID(00) TrackMode(tracking ) SigValue( 0) - Rcvr Status(1): - Antenna Voltage: 5000.00mV , Antenna Current: 0.00mA UCCM >DIAGnostic:LOG:READ:ALL? Log status: 22 entries L00:21/07/28.06:00:47 Self survey started L01:21/07/28.06:05:30 Ref Change: GPS L02:21/07/28.06:09:10 Ref Change: No reference L03:21/07/28.06:09:25 Ref Change: GPS L04:21/07/28.06:09:54 Ref Change: No reference L05:21/07/28.06:10:07 Ref Change: GPS L06:21/07/28.06:32:45 Ref Change: No reference L07:21/07/28.06:33:07 Ref Change: GPS L08:21/07/28.06:34:42 Self survey completed L09:21/07/28.06:36:13 Ref Change: No reference L10:21/07/28.06:36:25 Ref Change: GPS L11:21/07/28.06:58:13 Ref Change: No reference L12:21/07/28.06:58:25 Ref Change: GPS L13:21/07/28.07:07:27 Ref Change: No reference L14:21/07/28.07:07:43 Ref Change: GPS L15:21/07/28.07:31:43 Ref Change: No reference L16:21/07/28.07:31:55 Ref Change: GPS L17:21/07/28.08:35:59 GPS Antenna open L18:21/07/28.08:36:01 Ref Change: No reference L19:21/07/28.08:36:30 Ref Change: GPS L20:21/07/28.12:13:02 Output mode: Active L21:21/07/28.12:13:02 A/S change: Slave(HIGH) So far, so good. PS: I don't belive in magic, so I guess that some glue I used to hold the board, added some capacitive side effects.
[time-nuts] Re: Trimble GSPDO - ISSUE
I'm not worried about the F connector itself- rather, it's irresistible temptation to use wrong-impedance cables, often rather long ones. Agreed that LNA inputs don't tend to make good matches, but that's what the splitter largely addresses. It's the wrong impedance of the source that foils the benefit of the splitter, and which most people ignore altogether. I think we'd get along better if the antenna output impedance were 75 ohms, F connectors were used, and 75 ohm splitters were used. Then good isolation would be preserved at low cost no matter what load impedances were present on the splitter's outputs. The simple mismatch loss between 50 ohms and 75 ohms is pretty negligible in this context. When I see an attenuator with only about 15 dB return loss at L-band, it goes straight into the trash. To me, the anticipated main benefit of having a nanoVNA is that I'll be able to identify such defective items at flea markets before spending money on it. That is, if there are ever any more flea markets (because of Covid). I'm not optimistic. Dana On Wed, Jul 28, 2021 at 7:58 AM Bob kb8tq wrote: > Hi > > If you measure the input impedance of most low noise receivers, it’s not > going to be 50 ohms pure resistive. There are multiple reasons for this. > Since the “load” is not a match to either 50 or 75 ohm cable, it’s not that > big a deal. > > The amp in the antenna with it’s post filtering may or may not present a > 50 ohm source. They rarely hit a 14 db return loss spec in any case. Indeed > there are a lot of attenuators out there that don’t get to 14 db at 1.5 > GHz. > > Trimble did a *lot* of testing before they put the F connector on the > TBolt. > They could find no impact at all. > > Bob > > > On Jul 28, 2021, at 8:23 AM, Dana Whitlow wrote: > > > > Most general purpose passive splitters for the L-band regime are > > essentially variations > > on the Watkinson splitter, which provides good isolation between the > output > > ports, if > > (and only if) the input port is driven from a matched source. > > > > So if your GPS antenna, whether active or passive, has a good output > match > > then > > the Samsung's input impedance will not affect operation of the Trimble. > > But, again, > > this is true only if the antenna's output impedance is matched to the > > splitter's > > characteristic impedance (including consideration of any impedance > > transformation > > in the transmission line between the antenna and the splitter). > > > > I cringe at the cavalier treatment given to line impedances used in GPS > > systems. > > AFAIK, all GPS equipment is designed for 50 ohms, yet a great deal of > such > > equipment is provided with 'F' connectors, which invite the use of > > inexpensive RG-6 > > line, which is 75 ohm cable. In addition to problems with impedances and > > loading, > > It's a built-in source of multipath, all at no extra charge! > > > > Dana K8YUM > > > > > > On Tue, Jul 27, 2021 at 3:01 PM Don Cross wrote: > > > >> On Tue, Jul 27, 2021 at 2:54 PM ordnit via time-nuts < > >> time-nuts@lists.febo.com> wrote: > >> > >>> > >>> Any guess? Do I have to throw the unit from the window? For your > >>> reference, I have a samsung unit connected to same antenna via a > >>> splitter. The GPSDO is performing very well. > >>> > >>> > >> Hi Ordnit, > >> > >> I'm hardly an expert, but I wonder about the splitter. Is this a > passive or > >> active splitter? If passive, it could be the input impedance of your > >> Samsung is much lower than for your new Trimble and it is making the > signal > >> seen by the Trimble too weak. If you are willing to disconnect the > Samsung > >> temporarily, perhaps you could try connecting your antenna to the > Trimble > >> only and see what happens. > >> > >> Don > >> ___ > >> time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe > send > >> an email to time-nuts-le...@lists.febo.com > >> To unsubscribe, go to and follow the instructions there. > >> > > ___ > > time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe > send an email to time-nuts-le...@lists.febo.com > > To unsubscribe, go to and follow the instructions there. > ___ > time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send > an email to time-nuts-le...@lists.febo.com > To unsubscribe, go to and follow the instructions there. ___ time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send an email to time-nuts-le...@lists.febo.com To unsubscribe, go to and follow the instructions there.
[time-nuts] Re: Trimble GSPDO - ISSUE
Hi If you measure the input impedance of most low noise receivers, it’s not going to be 50 ohms pure resistive. There are multiple reasons for this. Since the “load” is not a match to either 50 or 75 ohm cable, it’s not that big a deal. The amp in the antenna with it’s post filtering may or may not present a 50 ohm source. They rarely hit a 14 db return loss spec in any case. Indeed there are a lot of attenuators out there that don’t get to 14 db at 1.5 GHz. Trimble did a *lot* of testing before they put the F connector on the TBolt. They could find no impact at all. Bob > On Jul 28, 2021, at 8:23 AM, Dana Whitlow wrote: > > Most general purpose passive splitters for the L-band regime are > essentially variations > on the Watkinson splitter, which provides good isolation between the output > ports, if > (and only if) the input port is driven from a matched source. > > So if your GPS antenna, whether active or passive, has a good output match > then > the Samsung's input impedance will not affect operation of the Trimble. > But, again, > this is true only if the antenna's output impedance is matched to the > splitter's > characteristic impedance (including consideration of any impedance > transformation > in the transmission line between the antenna and the splitter). > > I cringe at the cavalier treatment given to line impedances used in GPS > systems. > AFAIK, all GPS equipment is designed for 50 ohms, yet a great deal of such > equipment is provided with 'F' connectors, which invite the use of > inexpensive RG-6 > line, which is 75 ohm cable. In addition to problems with impedances and > loading, > It's a built-in source of multipath, all at no extra charge! > > Dana K8YUM > > > On Tue, Jul 27, 2021 at 3:01 PM Don Cross wrote: > >> On Tue, Jul 27, 2021 at 2:54 PM ordnit via time-nuts < >> time-nuts@lists.febo.com> wrote: >> >>> >>> Any guess? Do I have to throw the unit from the window? For your >>> reference, I have a samsung unit connected to same antenna via a >>> splitter. The GPSDO is performing very well. >>> >>> >> Hi Ordnit, >> >> I'm hardly an expert, but I wonder about the splitter. Is this a passive or >> active splitter? If passive, it could be the input impedance of your >> Samsung is much lower than for your new Trimble and it is making the signal >> seen by the Trimble too weak. If you are willing to disconnect the Samsung >> temporarily, perhaps you could try connecting your antenna to the Trimble >> only and see what happens. >> >> Don >> ___ >> time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send >> an email to time-nuts-le...@lists.febo.com >> To unsubscribe, go to and follow the instructions there. >> > ___ > time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send an > email to time-nuts-le...@lists.febo.com > To unsubscribe, go to and follow the instructions there. ___ time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send an email to time-nuts-le...@lists.febo.com To unsubscribe, go to and follow the instructions there.
[time-nuts] Re: Trimble GSPDO - ISSUE
Most general purpose passive splitters for the L-band regime are essentially variations on the Watkinson splitter, which provides good isolation between the output ports, if (and only if) the input port is driven from a matched source. So if your GPS antenna, whether active or passive, has a good output match then the Samsung's input impedance will not affect operation of the Trimble. But, again, this is true only if the antenna's output impedance is matched to the splitter's characteristic impedance (including consideration of any impedance transformation in the transmission line between the antenna and the splitter). I cringe at the cavalier treatment given to line impedances used in GPS systems. AFAIK, all GPS equipment is designed for 50 ohms, yet a great deal of such equipment is provided with 'F' connectors, which invite the use of inexpensive RG-6 line, which is 75 ohm cable. In addition to problems with impedances and loading, It's a built-in source of multipath, all at no extra charge! Dana K8YUM On Tue, Jul 27, 2021 at 3:01 PM Don Cross wrote: > On Tue, Jul 27, 2021 at 2:54 PM ordnit via time-nuts < > time-nuts@lists.febo.com> wrote: > > > > > Any guess? Do I have to throw the unit from the window? For your > > reference, I have a samsung unit connected to same antenna via a > > splitter. The GPSDO is performing very well. > > > > > Hi Ordnit, > > I'm hardly an expert, but I wonder about the splitter. Is this a passive or > active splitter? If passive, it could be the input impedance of your > Samsung is much lower than for your new Trimble and it is making the signal > seen by the Trimble too weak. If you are willing to disconnect the Samsung > temporarily, perhaps you could try connecting your antenna to the Trimble > only and see what happens. > > Don > ___ > time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send > an email to time-nuts-le...@lists.febo.com > To unsubscribe, go to and follow the instructions there. > ___ time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send an email to time-nuts-le...@lists.febo.com To unsubscribe, go to and follow the instructions there.
[time-nuts] Re: Trimble GSPDO - ISSUE
The status shown looks mostly ok. Reference is GPS, plenty of satellites tracked, signal levels ok, etc. Your antenna alarm is due to the 0ma current - should not be a problem. But… your XDOP values are all 0 which seems suspicious and the status is still ‘OCXO Warmup’ (not 100% on that since I don’t have a Trimble unit, only Samsung and Symmetricom). I would suggest that you eliminate the splitter and connect directly to your antenna, just to eliminate things. Also, the OCXO could be substantially off frequency. If possible, I’d measure the EFC voltage and frequency. The output from DIAGnostic:LOG:READ:ALL? would also be useful. You also might want to post to EEVBlog as there is a substantial thread on these UCCM units there at https://www.eevblog.com/forum/projects/a-look-at-my-symmetricom-gpsdo-(ocxo-furuno-receiver)/ > On Jul 27, 2021, at 2:54 PM, ordnit via time-nuts > wrote: > > Hi there, > thank you for valuable information I get everyday from the list. > > After a very long time I managed to power up a Trimble GPSDO, connected > to an aexternal antenna. > > UCCM >*IDN? > TRIMBLE,57964-15,86854165,V3.0.0.11-01 > Datecode: 0814 (pretty old, but still in its teen years) > > Some output from "common commands": > > UCCM >SYSTem:STATus? > > --- > 57964-15 serial number 86854165 firmware ver 3.0.0.11-01LINK mode > --- > Reference Status __ Reference Outputs > ___ > XX Ref 8KHz 0: [LOS] > XX Ref 8KHz 1: [LOS] TFOM 4FFOM > 1 > XX Ref 8KHz 2: [LOS] UCCM A Status[OCXO WARMUP] > XX Ref 8KHz 3: [LOS] > >> GPS: [phase:-3.3E-05, settling] > ACQUISITION ...[GPS 1PPS > Valid] > Tracking: 8 Not Tracking: 3 Time > > PRN El Az C/N PRN El AzGPS 11:44:34 27 Jul > 2021 > 32 39 107 46 3 10 226 > 1 28 284 3716 6 189ANT DLY 0 ns > 10 40 51 4214 8 327Position > 8 79 239 45 MODE Hold > 23 7 49 38 > 21 52 297 43 LAT N 43:35:11.819 > 27 55 153 43 LON E 13:31:1.250 > 22 32 230 41 HGT +225.27 m (MSL) > > > ELEV MASK 5 deg > --- > > UCCM >POSSTATus > > - > 07/27/2021 11:44:57 > - > Position: LAT(N 43:35:11.819) LON(E 13:31:1.250) H(+225.27 m MSL) > - > Geometry: PDOP(0.0) HDOP(0.0) VDOP(0.0) > num of visible sats > 10 > num of sats tracked > 10 > Receiver Channel State > CH 0 > SateID(03) TrackMode(pos avail) SigValue(36) > CH 1 > SateID(32) TrackMode(pos avail) SigValue(47) > CH 2 > SateID(01) TrackMode(pos avail) SigValue(37) > CH 3 > SateID(16) TrackMode(pos avail) SigValue(34) > CH 4 > SateID(10) TrackMode(pos avail) SigValue(42) > CH 5 > SateID(08) TrackMode(pos avail) SigValue(44) > CH 6 > SateID(14) TrackMode(tracking ) SigValue(20) > CH 7 > SateID(23) TrackMode(pos avail) SigValue(37) > CH 8 > SateID(21) TrackMode(pos avail) SigValue(44) > CH 9 > SateID(27) TrackMode(pos avail) SigValue(43) > CH 10 > SateID(22) TrackMode(pos avail) SigValue(40) > CH 11 > SateID(00) TrackMode(tracking ) SigValue( 0) > - > Rcvr Status(1): > - > Antenna Voltage: 5000.00mV , Antenna Current: 0.00mA > > UCCM >status > > - UCCM Slot STATE- > > 1-1. #Now ACTIVE STATUS [OCXO Warm] > 1-2. #Before ACTIVE STATUS - [Alarm] > 2-1. #Reference Clock Operation [Not Used] > 2-2. #Current Reference Type --- [GPS] > 2-3. #Current Select Reference - [GPS 1PPS] > 2-4. #Current Reference Status - [Good Accuracy & Stable] > #GPS STATUS --- [Available] > #Priority Level --- [LINK > GPS] > #ALARM STATUS > #H/W FAIL [ LINK ] > #OPERATION ALARM -- [Antenna] > 3-1. #PLL STATUS --- [DISABLE] > 3-2. #Current PLL MODE - [OFFSET OBSERVATION MODE] > > > The issue I'm facing is following: even after a long uptime, I never com to a > "fast blinking led" and PLL status "enabled". Monitoring device with LHv6, > shows an "operation mode" alternating Locked (few seconds" and "recvery". > TFOM is quite always 3 or 4. Power supply is linear, with output voltage 5.6V > or 6V. I made
[time-nuts] Re: Trimble GSPDO - ISSUE
On Tue, Jul 27, 2021 at 2:54 PM ordnit via time-nuts < time-nuts@lists.febo.com> wrote: > > Any guess? Do I have to throw the unit from the window? For your > reference, I have a samsung unit connected to same antenna via a > splitter. The GPSDO is performing very well. > > Hi Ordnit, I'm hardly an expert, but I wonder about the splitter. Is this a passive or active splitter? If passive, it could be the input impedance of your Samsung is much lower than for your new Trimble and it is making the signal seen by the Trimble too weak. If you are willing to disconnect the Samsung temporarily, perhaps you could try connecting your antenna to the Trimble only and see what happens. Don ___ time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send an email to time-nuts-le...@lists.febo.com To unsubscribe, go to and follow the instructions there.
