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

[Robert Atkinson]

Hi Herbert,
These units are different to the picture at 
http://www.qsl.net/z/zl1bpu/PROJ/FE5650-2.jpg
They have dip switches and no PIC. The option is covered in one of the manual out there but I'm sitting at the wrong computer to dig out the details.

Robert G8RPI.




________________________________
 From: Herbert Poetzl <herbert at 13thfloor.at>
To: Discussion of precise time and frequency measurement <time-nuts at febo.com> 
Sent: Sunday, 7 April 2013, 15:10
Subject: Re: [time-nuts] Changing FE-5650A frequency?
 
On Sun, Apr 07, 2013 at 11:27:23AM +0100, Alexander Wright wrote:
> 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.

The baseplate (2xLM2941, LP2952) basically is the power
supply/regulation, so nothing interesting there.

> 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? 

The purpose of the polymer foam is isolation to keep a 
stable temperature throughout the boards.

http://www.qsl.net/z/zl1bpu/PROJ/FE5650-2.jpg

The top layer in this image is the DDS board, and it is
basically identical to the FE5680A, which means it can
be adjusted in a wide range, but only does digital synthesis
based on the reference frequency.

But let's see what Bill says to the pictures ... :)

best,
Herbert

> 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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