[time-nuts] LTE-Lite Plans

Jim Miller jim at jtmiller.com
Tue Nov 25 14:42:42 EST 2014

I have one of the LTE-Lite 20Mhz units and plan to use it as a frequency
reference for my ham radio gear. My planned setup is as follows:

I'm putting it in the recommended Hammond enclosure powered by a USB cable
from my PC. I had originally planned to use the wall wart provided but I
want to get status from the unit without hacking a window in the top to see
the LEDs so I plan to use TBD software to provide a status check. I briefly
thought about doing something with an Arduino and display shields but that
seemed like too much work for now.

I'm using a inverting D FF from TI (SN74aup1g80) as a divide by 2 to
provide 10Mhz. The chip and associated passives will be on a little circuit
board mounted in the open area normally reserved for the external
oscillator. The output of the chip will be connected via a series resistor
of about 400 ohms to a SMA connector. This resistor will limit the load on
the FF and the LTE-Lite power source. Power will be taken from C6.

This output will only go a few inches to a DEMI 10Mhz 4 way splitter The
input of the splitter will be equipped with an additional ERA-2+ amplifier
(50 ohm input) which will restore the signal levels lost due to the series
resistor in the LTE-Lite addon. The DEMI splitter will also be equipped
with a manual power switch which will allow me to kill the output of the
box if the GPSDO fails for some reason.

The little hockey puck antenna will be mounted directly outside the shack
wall near a south facing wall which will limit the visibility to only half
the horizon. I'm assuming this will be enough for my modest needs.

The four outputs will be used as follows:

One will go to the K3 ExtREF to provide an external reference.

Two will go to separate TX/RX converters for low frequency (<600Khz) use
and be used with the transverter I/O on the K3.

The last will be used as a general calibration reference.

When the power switch on the DEMI splitter is turned off the K3 will revert
to using its internal TXCO.

I leave the PC running 24/7 and the power to the LTE-Lite would only be
interrupted when the PC is rebooted. I don't need a frequency reference
during the reboot time since I always operate my rig with the PC on and
running. The TBD status software will tell me when the LTE-Lite is synched
up again. The PC is served by a UPS and the shack circuit is one which is
served by our whole house generator.

I have the DEMI splitter built up and working. Now just waiting on
enclosure from Digikey. I should have everything running by mid December.

I still need to figure out what to use for the status software. Ideally I'd
like an applet to display appropriate status indications on my monitor for
now I'll examine the uBlox and Putty and if not satisfactory perhaps I'll
write something in VB.

Feedback and suggestions welcome.


Jim ab3cv

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