[time-nuts] Spectracom 8140T Line Tap Schematic

Julien Goodwin time-nuts at studio442.com.au
Thu Jun 14 10:53:52 EDT 2018


On 14/06/18 23:31, gandalfg8--- via time-nuts wrote:
> Earlier replies that discussed removing the DC supply from the 8140 outputs gave me the impression your requirement was to connect directly the outputs of the 8140 without line tap modules, which is what I was addressing with my recent suggestion of a series capacitor, but can see now that's not the case.

I think that was a digression from my post, I'm planning to use the 8140
as-expected by Spectracom.

> The VersaTaps phase lock an internal crystal, any frequency between 4 and 20MHz, to the 10MHz input and then provide an output at the crystal frequency or the crystal frequency divided by a fixed integer between 1 and 8,192, so in that sense yes they're a synthesiser but the few I've seen were still supplied preset for a specific frequency.

Ah, yes, that design would make a lot of sense. I was imagining a more
modern design you might do these days.

> However, "versatile" does not necessarilly mean quick or convenient to reprogram.
> Aside from perhaps needing  to change the crystal the division ratio needs to be set by adding or removing links across pairs of holes in the circuit board. Those holes are on a standard 0.1inch pitch so fitting headers that would take shorting links should be straightfoward enough, and I suspect what was originally intended, but the units I have were supplied preprogrammed using resistor style wire ended zero ohm links mounted above the circuit board and soldered from below. Reprogramming one of these would involve unsoldering and perhaps removing all the connectors etc in order to remove the circuit board, so I'd certainly make darn sure they had headers fitted before being returned to the box!

I'm going to have to do something very similar to the 8140 when it
arrives, as I bought one set for 1MHz input, and I'm going to
(initially) be feeding it 5MHz from an FRK.



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