[time-nuts] problem with Efratom FRS-C from eBay

[Robert Darlington]

Okay, my first mistake here was not having a terminator when looking at it
on the scope, but it was terminated at 50ohms when attached to the counter.
This looks much nicer:

http://www.nerdhouse.org/frsc.jpg

Turning off the 20MHz bandwidth filter cleaned it up to what you see
there.   When I gate the frequency counter with the 1PPS signal from the
Lassen iQ, I'm getting 10,000,000 +/- 1Hz counts. This seems reasonable, as
that fits the spec of the counter (HP 5335A).  When counting using the
internal TCXO which may be way off, I'm getting 9,999,975.55 Hz +/- 0.06Hz
give or take).

When I first powered it on I did see the frequency swing to either side of
10MHz and settle down a bit, then settle down some more.  The last digit
moves a bit, sometimes moving the one before it (0.xx Hz).  Maybe this thing
IS working and is measuring the stability of the oscillator in the counter.
I still see nothing on the lock line but it may need a pull up resistor.
I'll play around with it some more.  I'm getting dragged to dinner so I
can't play anymore tonight.

Thank you all for the help and suggestions.  I'm very green but am learning.

-Bob

On Fri, Oct 17, 2008 at 5:24 PM, Hal Murray <hmurray at megapathdsl.net> wrote:

>
> > The unit that I received does not show TTL after the frequency and the
> > scope output looks like a cross between a sinewave and a ringing
> > square wave.  I have about 13 feet of RG174 between the FRS and the
> > measurement equipment so who knows.
>
> Do you have a terminator at the far end of the coax?
>
> What does it look like with a scope directly at the unit without any coax?
>
>
>
>
> --
> These are my opinions, not necessarily my employer's.  I hate spam.
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