[time-nuts] 2.5 Ghz 12 digit counter project

Orin Eman orin.eman at gmail.com
Fri Dec 28 03:22:58 UTC 2012

On Thu, Dec 27, 2012 at 6:45 PM, Tom Harris <celephicus at gmail.com> wrote:

> Watch out for Silicon Chip designs, they have a habit of not making the
> source code available, which you only find out at the end of the project. I
> suppose that it is to allow the author to make a few extra $$ selling
> programmed micros. They had a nice 3 phase inverter design a year ago that
> had this problem, I wrote to the author promising not to distribute the
> source, I just wanted to read it, but didn't even get the courtesy of an
> answer.
> I suspect that this counter is like the inverter, an oldish design that is
> not worth building as you can get the same for half the cost out of China.
> What makes it worthwhile is getting the hardware & the source code, so that
> you can tinker with it.

I have a 2.7GHz counter out of China and cannot recommend it.

If I feed it 10 MHz from a OCXO that is within 1Hz (as checked on my 5335A
with high stability timebase), the counter will read fine for a while, then
the reading will start drifting upwards and become unstable.  I forget how
high the reading drifts, hundreds of Hz at least.  It will count to at
least 2.7GHz, but I cannot trust it.

It also has a 13 MHz output on the back.  I looked at it on my TDS210
digital scope and there is a glitch on the leading edge of the waveform!
It clearly goes up, returns to zero then finally goes back up for the rest
of half a period.  Whether this glitch affects the gating, I don't know.
It's possible it is generated in whatever circuit buffers the clock for the


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