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

Alexander Wright alecjw at gmail.com
Sun Apr 7 06:27:23 EDT 2013


On 07/04/13 05:01, WB6BNQ wrote:
> 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.
>

Bill,
Thanks for your reply! Here are some photos of the inside: 
http://m0tei.co.uk/fe5650pics/
You'll see that it comes with a custom machined plate screwed onto the 
front - this was how it was mounted in the thing i pulled it out of. It 
can be removed but i found it easier to take the thing apart with it on. 
A thermostatic switch used to bolt onto it to (presumably) act as a 
thermal cutout.
You'll also notice that the boards we're probably interested in are 
potted it some sort of white compound - it's hard but crumbly - feels 
like some sort of polymer foam. I've started to pick it off a bit but 
could you just confirm that this is actually a sensible thing to do 
before I go all out scraping it off? Thanks!

> 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.
>

This unit is probably from late 1996/1997 if that helps?

> 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
>

Awesome, looks like there's some great info there! Unfortunately i'm not 
sure hoe relevant it is to mine since my option doesn't seem to do RS232....


On 07/04/13 04:17, Herbert Poetzl wrote:
 >
 > Open it up, take some nice pictures of the circuit boards
 > and components and I can probably tell you what might be
 > possible (after looking at them :).
 >

Thanks Herbert! Pictures above^

 >> As far as i'm aware this model doesn't have serial control.
 >
 > best,
 > Herbert
 >

Best regards,
Alec




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