[time-nuts] LTE-Lite Plans

Said Jackson saidjack at aol.com
Wed Nov 26 12:34:29 EST 2014


Sent From iPhone

> On Nov 26, 2014, at 9:20, Didier Juges <shalimr9 at gmail.com> wrote:
> Said,
> 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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