[time-nuts] Small Symmetricom GPSDO

Bryan _ bpl521 at outlook.com
Sun Feb 21 16:23:11 EST 2016


John:
I have one of these and I really like the compact unit. I don't have any equipment to compare it's accuracy other than my Nortel GPSDO and watching them both on the scope. If you follow this thread there is a number of tips and commands on the use of the RS232 output. There is also a switch on the side that will give you a 10Mhz output if there is no antenna present. 
http://www.eevblog.com/forum/projects/a-look-at-my-symmetricom-gpsdo-(ocxo-furuno-receiver)/

-=Bryan=-

> Date: Sun, 21 Feb 2016 11:55:59 -0600
> From: wpxs472 at gmail.com
> To: time-nuts at febo.com
> Subject: [time-nuts] Small Symmetricom GPSDO
> 
> I have been playing with one of those small, 2.75"by 4.5" GPSDOs that are
> being sold on that auction site. Most of the ones I have seen any
> discussion about have been Trimble, but this Symmetricom one looks similar
> but is about half price. I have hooked it up a few times to see how fast it
> can find satellites and how the LEDs work. Yesterday, I hooked it up and
> compared the 10 MHz output to my Z3801 which has been running for about a
> month now. I am using my Racal 1992 counter in time difference mode. It has
> a resolution of 1 ns. The 10 MHz isn't present until it has "locked"on
> satellites. Or at least I presume that is it. I didn't get any 10 MHz for
> about the first 10 minutes. At first, it looked pretty stable. Then, I
> decided it wasn't.  Now, I'm not sure. It acts differently to the Tbolt I
> tested in the same manner before. While the Tbolt would sit steady on some
> arbitrary time difference for maybe a half hour and then move 30
> nanoseconds or so in a minute only to settle down again for a while, this
> thing just slowly drifts back and forth. After thinking about it, I think
> that is how it was meant to operate. It seems to have been an internal
> piece of some other, larger piece of equipment. In that role it was most
> likely meant to provide either 1 PPS, 10 MHz, or both at pretty good
> accuracy pretty quickly after getting power. It isn't as good as say a
> Z3801, but then I don't think it was meant to be either. It certainly isn't
> nearly as big. I may put it in a case with a power supply and a buffer amp
> and use it for an everyday standard. I certainly think it is good enough
> for that. It seems happy running on 6.3 volts at around 600 ma. after warm
> up. Has anyone else had any experience with one of these? What did you
> think of it?
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