[time-nuts] Shera revisted

Joakim Langlet joakim.langlet at seaview.se
Wed Aug 10 17:30:50 EDT 2016

Dear time-nuts,

My name is Joakim Langlet (SM0OET) and I just recently joined this list. 
As Brooks Shera was mentioned, I remembered that I was referenced in the 
footnotes of the original article in the QST - July 1998. It feels 
almost historical now. Brooks bought a few OCXOs from me.

I am currently working on a GPS stabilized OCXO.
It is based on a Xilinx Zynq FPGA as the processor and counter arrangement.
The hardware is starting to take shape. The control voltage of a 20 MHz 
OCXO is set by a DAC coupling from which I hope to set the voltage in 
very small steps.
The OCXO has a CMOS level output which is converted to LVDS and is wired 
to the FPGA board. The Xilinx Zynq take a minimum frequency of 19 MHz as 
input to the PLL of the clock tile. My intention is to scale up the 
clock to some where a bit over 200 MHz to be fed to the counters.The 1 
PPS from the GPS receiver is also fed into the FPGA to gate the counters.

The reason for my choice of processor is that I want to run Linux on it 
in order benefit from the large software base. Time distribution using 
PTPv2 and a nice web-application to visualize and control what is going 
on inside is part of the intended concept.

I still have a long way to the finish line but I will try to present 
some results as I proceed.

I am following what is written on this list with great interest. It 
feels good to know that I am not the only nut ....


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