[time-nuts] LTE-Lite Plans

Didier Juges shalimr9 at gmail.com
Wed Nov 26 12:20:33 EST 2014


Your drawing looks better than those by Bob Pease, and he was never
embarrassed by his :)
Thank you for your extensive contributions to time nuts

Didier KO4BB

On Tue, Nov 25, 2014 at 7:28 PM, S. Jackson via time-nuts <
time-nuts at febo.com> wrote:

> Guys,
> I never expected such an intense discussion about using and buffering  the
> outputs from the LTE-Lite board since the actual circuit to use can  be
> quite simple.
> To address these questions, I drew up a simple schematic that uses a DIP-14
>  74AC04 gate, six resistors, and two caps. Everyone who can solder should
> be able  to build this simple circuit as a dead-bug type build on a
> copper-clad  board.
> This circuit will buffer all three outputs (1PPS, TCXO RF, and Synthesixed
> RF) of the LTE-Lite eval board with CMOS 3.0V levels that can drive 50 Ohms
>  terminations. For simplicity I grab the 3.0V power from the DIP-14 TCXO on
> pin  14 of that part on the eval board, even though I would strongly
> suggest to use a  separate low noise 3.3V or 5V power supply to power the
> 74AC04
> chip.
> You can add 100nF caps in series to the two RF signals before they feed
> into the coax output connectors for less power consumption and removing DC
> for
>  instruments that don't like DC inputs.
> Using a single IC for the three signals will result in crosstalk between
> the signals, but it should be clear from the schematics how one could break
> up the signals by using three independent ICs to minimize crosstalk.
> We use this circuit in a small box here using SMT components, and it works
> really well.
> Excuse my horrible writing, using keyboards has made my fingers  numb..
> Hope that helps,
> Said
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