[time-nuts] Remote GPS Oscillator Steering

Bob Camp lists at rtty.us
Thu Apr 18 11:32:19 UTC 2013


Hi

By the time you drop to 1 pps, transport the 1 pps, and lock a 10 MHz back up to it, you have done a lot of stuff. The work and the cost of the bits and pieces will add up. If the 10811 is the ultimate source, it's not going to be at GPSDO performance levels. A hundred dollar or so GPSDO would probably be less hassle and not much more cost.

That said, yes you can feed signals over the twisted pair. If the only real need is to *check* the 10811, any frequency the counter will count is fine. PPS works as well as anything. I'd pick something I could transformer couple. 

Bob

On Apr 18, 2013, at 4:35 AM, Iain Young <iain at g7iii.net> wrote:

> Hi Everyone,
> 
> Recently, I have acquired a HP Frequency Counter and Signal Genny, and
> have set up a small "lab" in the house. This is great, but I'd like to
> hook it into my 3816A, which is 70 ft away in an outhouse, along with
> all my radio gear, to at least compare it to the 10811 in the Frequency
> Counter.
> 
> 
> I'd rather not drill a hole and run a cable (There are other issues
> with that as well as the hole, the outhouse is the other side of the
> garden path from the lab!)
> 
> I do have fibre to the house for N/W  connectivity, and (unshielded)
> CAT6 from the patch panel to the "lab".
> 
> Two problems here. One the patch panel is the other side of the house
> from the lab (so running a dedicated piece of coax is out without
> taking up the floors..), and Two, 10MHz over unshielded CAT6 is not
> good practice, to say the least, and simply not going to happen.
> 
> So I started looking at other possibilities. It seems a lot of GPSDOs
> steer the Oscillator by using the PPS. Is that right ? 1 Hz over UTP is
> a bit more reasonable than 10 MHz, but I did not find many 10MHz
> oscillators with a PPS input.
> 
> 
> I thought of using a Z3801 instead of the Z3816, but patching out from
> the EFC SBM connector, then (optionally) converting that to fibre,
> sending it up the garden to the house, converting back to copper, then
> the CAT 6 to the Lab where a second Z3801 would sit
> 
> I would rather fibre between the house and outhouse for EMC and
> grounding reasons. My hope is that thee 10MHz Osc would then be steered
> from the remote Z3801, although the lab Z3801 itself would complain
> bitterly about no lock no doubt.
> 
> 
> Does anyone have any comments on this madhat scheme ? Or have other
> suggestions of how I might go about getting that 10MHz signal
> converted to fibre, and back again to send into the "lab" equipment ?
> What are other people's experience with similar issues ?
> 
> What do the "big boys" like NIST and NPL do to manage this ? I know
> they transfer time over large distances, and I know NPL transfer
> frequency as well to certain customers, so I guess other similar
> institutions do as well
> 
> 
> [Note, for me, plug and play is better. Soldering irons do not like me,
> and I wouldn't trust myself with one anywhere near anything like a
> precision instrument :), although putting pre-built modules in a metal
> box I'm okay with, but plug-and play preferred.]
> 
> (Googling for fibre converters or similar these days brings up such
> a noise floor of Ethernet, Any suggestions on the best terms
> or part numbers to use to find raw (assembled) fibre transmitter /
> receiver modules that might be suitable would be gratefully received)
> 
> 
> Best Regards
> 
> Iain
> 
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