[time-nuts] Changing FE-5650A frequency?

WB6BNQ wb6bnq at cox.net
Sun Apr 7 00:01:48 EDT 2013


Hi Alec,

You may be in luck.  However, I would need some additional pictures, particularly
of the connector on the bottom, also some of the inside.

The primary physics package is a stand alone analog Rubidium frequency standard
that outputs 50.255* MHz frequency.  That signal is used to drive various output
board configurations, included inside the unit, to provide a customer required
output frequency.  The more recent revised units (they look the same) use a new
digital scheme that is much more of a hassle.

The one that I and a number of people are familiar with is the 5650-option-58
model whose output was a 1pps.  To get the 1pps the 50.255+ MHz signal was used
to drive a Direct Digital Synthesizer (DDS) that produced 8.3+ MHz signal that
was then divided down via normal TTL dividers to produce the 1pps.  The DDS is
capable of being changed to other frequencies up to about 20 MHz, however, the
filter following the DDS needs to be changed or bypassed to properly filter the
new frequency.  Bypassing is the easiest method but would require using an
external filter to get rid of aliasing and spurs.

I put together a zip file of various information on FEI-5650-option 58 that will
help you get familiar with the family line.  If you have problems with the link
let me know.  Also, after you get a successful download let me know so I can
reduce the FTP storage level, thank you.

http://pages.suddenlink.net/stevewingate/cryptic1/for alec on 5650-option-58.zip

Bill....WB6BNQ

Alexander Wright wrote:

> Hi all,
> I've recently ripped some FE-5650A's out of some old equipment, but they
> seem to be a custom build, here you can see they have the option just
> listed as "-":
> http://cambridge.m0tei.co.uk/files/IMG_20130330_232647.jpg
>
> They seem to be single rail (15v) supply with an 800kHz output. I
> wonder, does anyone know if it's possible to change its frequency? As
> far as i'm aware this model doesn't have serial control.
>
> Thanks,
> Alec M0TEI
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