[time-nuts] Remote GPS Oscillator Steering

[Hal Murray]

> I'd rather not drill a hole and run a cable

You can feed the cable through a window or door and across the grass long 
enough to make an occasional measurement to tell you how accurate and stable 
the local oscillator is.


> 10MHz over unshielded CAT6 is not good practice, to say the least, and
> simply not going to happen.

What do you mean by "not good practice"?

Gigabit Ethernet works over CAT5.  I think it's 125 megabaud, 5 level, 2 bits 
per baud.  Whatever, it's way over 10 MHz.

Here are some scope pictures of a PPS signal from a TBolt over 100 ft of 
Cat5e and Cat6.
  http://www.megapathdsl.net/~hmurray/time-nuts/coax/TP-20ns.png
  http://www.megapathdsl.net/~hmurray/time-nuts/coax/TP-100ns.png
  http://www.megapathdsl.net/~hmurray/time-nuts/coax/TP-1us.png

That was clipleaded together on the bench.  (I did adjust things until the 
termination was clean and kept the clipleads short.)



> 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. 

I can't figure out what you are trying to do.  The lab Z3801 isn't setup to 
be steered by an external PPS or 10 MHz signal.


> 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 ? 

I think you want to send 10 MHz from your outhouse to your house/lab.  You 
may need a distribution amplifier if you want to send it to more than one 
device.

Fiber transmitters and receivers are reasonably common.  You can get modules 
targeted at Ethernet with both transmit and receive in the same package.  
There is a blizzard of variations depending on distance and bit rate and type 
of fiber.  The trick is that the receiver includes AGC so you get logic level 
signals out.

You can get separate transmit and receive modules.  I haven't looked at that 
area for 15 years.  Back then LEDs over multimode fibers at 155 megabits for 
a km was one sweet spot.  For longer or faster, you needed single mode and 
lasers which were a lot more expensive.  10 MHz will be easy.

Depending on your existing fiber connectors and/or the parts you find, it may 
be cheaper to get official Ethernet parts and throw away the other half 
rather than get adapter cables to match cheaper separate parts.



-- 
These are my opinions.  I hate spam.