[time-nuts] Spectracom 8140T Line Tap Schematic

Bob kb8tq kb8tq at n1k.org
Fri Jun 15 08:59:53 EDT 2018


Hi

The typical 8140 tap has an ADEV of around 2x10-11 at a tau of 1 second and is in the 3x10^-12 range at 100 seconds. That’s not super duper, 
but it’s plenty good enough for the intended use of feeding racks full of test gear. If you are feeding it with a typical Cs or telecom Rb, it’s about 
as good as the source you are feeding it with.

On the plus side, if you have an inventory of gear needs 100 KHz as a reference, just grab that tap. This other device needs 1 MHz, grab the tap.
That one needs 5 MHz …. It’s tough to do that with other systems.

Bob

> On Jun 14, 2018, at 9:41 PM, Charles Steinmetz <csteinmetz at yandex.com> wrote:
> 
> Julien wrote:
> 
>> I'm somewhat tempted to take the schematic and see if I can fit it in
>> the comparatively tiny Pomona boxes
> 
> Before getting too excited about the various 8140 module designs, it may be worth reflecting that the performance of the 8140 system is mediocre at best from a time-nuts perspective.  There are lots and lots of much better designs if you're building your own.  Even something as simple as a modified video distribution amplifier can be orders of magnitude better (see, e.g., <http://www.ko4bb.com/getsimple/index.php?id=download&file=02_GPS_Timing/Extron_ADA_6_modifications_for_use_as_10MHz_distribution_amp_STEINMETZ.pdf>).
> 
> The point of the 8140 system is that it is a moderate performance, "do everything" solution for large installations (hundreds of potentially multifrequency taps spaced around acres of facility), not a time-nuts-quality distribution system for a facility the size of a residential home.
> 
> Best regards,
> 
> Charles
> 
> 
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