Symmetricom 12V GPS antenna? - Page 1
Forum section: electronics / general

author: notfaded1
author_rank: Frequent Contributor
timestamp: November 29, 2019, 05:01:39 pm
content: I recently acquired a symmetricom syncserver S250 with the rubidium occillator. It's not coming with the antenna. I know they use BNC connection with 12V antenna per the manual. Most of the replacements I can find are one of these two:142-614-50142-618-50Are there any other good ones that are 12V anyone recommends? I also noticed there are some window mount ones you can use:Symmetricom A205-001G1 Timesource 2500 - GPS Window AntennaFor use at home use as master clock does anyone have experience with these 12V antenna and have any advice? I've been considering how to run the cable through the wall or somehow to get out of the house.Thanks,Bill

author: notfaded1
author_rank: Frequent Contributor
timestamp: November 30, 2019, 06:19:35 pm
content: It seems hard finding antenna that can handle 12V plus and I thought maybe someone might have a suggestion that has more experience than me? Maybe that's not welcome as a non EE here? Well I really like the stuff anyhow.Bill

author: testpoint1
author_rank: Frequent Contributor
timestamp: December 02, 2019, 03:45:31 am
content: I think can change the circuit to 5V or 3.3Vupdate 12/19/2021I got a symmetricom truetime timevault, it used a 12V GPS antenna, the antenna is quite old and expensive, just change the circuit to 3.3V, add a NCP1117 and a capacitor (10uF), very easy.https://www.eevblog.com/forum/metrology/change-the-12v-gps-antenna-port-to-3-3v-symmetricom-truetime-timevault/new/#new

author: Marck
author_rank: Regular Contributor
timestamp: December 02, 2019, 04:17:14 am
content: We use a antenna from Rojone on our semetricom gear. You could check the web to see what they offer. I cant seem to track down the part number.M

author: FriedLogic
author_rank: Regular Contributor
timestamp: December 04, 2019, 09:07:10 pm
content: I'd wait until the S250 turns up and then check what voltage it actually has on the antenna output, both unloaded and with a suitable load like 50mA.Many of the GPS receivers for surveying put out more than 5V, so many of the antennas for them will accept 12V. You need to check for the specific one that you're thinking of buying since there can be different variations, custom models, product changes, etc. Lots of cheap surplus stuff out there.I don't know if all the cheap new ones that claim a wide operating range actually are.I didn't notice the required antenna gain mentioned, but in the picture of the insides of the unit it looks like it has a Motorola M12/M12+ receiver. If it's an M12+, you would be wanting a gain of about 18-36dB at the receiver input, so that plus cable and any other losses for the actual antenna gain.

author: 8bit
author_rank: Newbie
timestamp: July 15, 2020, 03:20:56 pm
content: The Symmetricom SyncServer S200/S250/S300/S350 (and others) do add 12V to the GPS antenna BNC connector. Almost everyone else uses 5V (including older Symmetricom).You can use a DC blocker on the BNC and then add 5V to your antenna feed and use any antenna you like.Or you can hack the unit and reconnect the bias from a 12V source to a 5V source on the main board.I have several 5V and 12V GPS systems connected to the same antenna so I needed one that worked for all at the same time. I already had the Symmetricom 58532A antenna installed so I modified the antenna to work with 12V (5-15V +-10%). It just requires removing 2 chips (resistor and TVS) and adding 4 chips (VR, Caps, new TVS).I use the the modified 58532A antenna and 58529A booster with 100+ feet of RG-6QS (yes, I know it's 75 ohm), grounding block, active splitter and several adapters. It works well for any GPS unit I connect (Trimble, TrueTime, Motorola, Ublox, Symmetricom, etc).

author: notfaded1
author_rank: Frequent Contributor
timestamp: July 15, 2020, 06:35:22 pm
content: Another trick I've found (especially since sometimes I have multiple GPS and GNSS DO's running at the same time):HP, Symmetricom, and now Microchip/MicroSemi:58535A 2 way58536A 4 way58517A 8 wayAs long as you have one device powering the antenna you can can have other devices connected and getting the signal passed through to them and it'll block the voltage from other attached GPSDO's. Also you can daisy chain these as well.I bought newer GNSS multiple signal compatible splitter from company called GPSSource a 4 x 1 splitter with all SMA connectors on it instead. Nice if you want L1/L2/L5 and variations.

author: DaJMasta
author_rank: Super Contributor
timestamp: July 15, 2020, 09:00:52 pm
content: I would also check to make sure there is no LO coming out of the antenna port. I've worked with a couple of TimeSource 3500 modules that backfed an LO through the nonstandard voltage antenna port for an external downconverter - especially useful with very long cable runs. If this is designed to power an antenna directly, then it is likely switchable inside the unit (or at least can be with the right resistor or something).An other option would be a DC block and your own power injector (can be found as bias tees), or a commercially made amplifier with the right configuration. My home installation uses a GPS Networking branded 20dB amplifier that includes a DC block on the output side and a DC supply for the antenna (which actually uses a variable regulator so you can switch it to whatever you need with a resistor).