[time-nuts] Changing FE-56XX frequency

Mon Apr 8 15:53:16 EDT 2013

As Bill suggests, the best way to achieve any-frequency performance with the 
newer FE-56xx devices is to pull out the Rb reference frequency and run an 
external DDS off it.

I found that the Rb loop frequency in the one I played with was exactly 
60MHz, rather than the 50.255MHz of the older units, although it doesn't 
really matter what it is. I run mine with an AD9852 in x4 mode (so the clock 
is 240MHz), and so have a range of 0 - 90MHz. The only control software I 
have at present is the dreadful parallel port program which came with the AD 
development kit, so it is useful only as a signal generator. One day I'll 
write it something better.

73,
Murray ZL1BPU

----- Original Message ----- 
From: <time-nuts-request at febo.com>
To: <time-nuts at febo.com>
Sent: Tuesday, April 09, 2013 4:00 AM
Subject: time-nuts Digest, Vol 105, Issue 22

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> Today's Topics:
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>   1. Re: Changing FE-5650A frequency? (Don Latham)
>   2. Re: Trimble SVeeSix -- was DATUM 9390-52054 Grief again...
>      (Brooke Clarke)
>   3. Re: Changing FE-5650A frequency? (WB6BNQ)
>   4. Re: Lady Heather (Achim Vollhardt)
>
>
> ----------------------------------------------------------------------
>
> Message: 1
> Date: Sun, 7 Apr 2013 15:29:46 -0600 (MDT)
> From: "Don Latham" <djl at montana.com>
> To: "Discussion of precise time and frequency measurement"
> <time-nuts at febo.com>
> Subject: Re: [time-nuts] Changing FE-5650A frequency?
> Message-ID:
> <1e9644594b69bd93447cb42b0d60444d.squirrel at webmail.montana.com>
> Content-Type: text/plain;charset=iso-8859-1
>
> wow, a little more picking will get you to the dds pinout wrt the 24-bit
> programming word...
>
> Alexander Wright
>> On 07/04/13 15:10, Herbert Poetzl wrote:
>>> 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
>>>
>>
>> Herbert, the board doesn't seem to be the same, the chips which are
>> visible don't line up with the ones in that picture. Anyway my curiosity
>> got the better of me and I dug through the foam some more to find a long
>> row of DIP switches. I bet i can change the divider ratio with some
>> combination of those:
>> http://m0tei.co.uk/fe5650pics/IMG_20130407_170929.jpg
>>
>> Also, you can see that the chip is an AD9955 DDS chip:
>> http://novatech-instr.com/PDF_files/AD9955.pdf
>>
>> -
>> Alec
>>
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>
> -- 
> "Neither the voice of authority nor the weight of reason and argument
> are as significant as experiment, for thence comes quiet to the mind."
> De Erroribus Medicorum, R. Bacon, 13th century.
> "If you don't know what it is, don't poke it."
> Ghost in the Shell
>
>
> Dr. Don Latham AJ7LL
> Six Mile Systems LLP
> 17850 Six Mile Road
> POB 134
> Huson, MT, 59846
> VOX 406-626-4304
> www.lightningforensics.com
> www.sixmilesystems.com
>
>
>
>
> ------------------------------
>
> Message: 2
> Date: Sun, 07 Apr 2013 15:21:58 -0700
> From: Brooke Clarke <brooke at pacific.net>
> To: Discussion of precise time and frequency measurement
> <time-nuts at febo.com>
> Subject: Re: [time-nuts] Trimble SVeeSix -- was DATUM 9390-52054 Grief
> again...
> Message-ID: <5161F186.9000309 at pacific.net>
> Content-Type: text/plain; charset=ISO-8859-1; format=flowed
>
> Hi:
>
> I spent a lot of time with the SV6 learning about GPS.
> http://www.prc68.com/I/Trimpack.shtml#SV6
>
> Note:  The Trimpack web page has a bunch of Trimble GPS receivers, not 
> just Trimpacks.
>
> Have Fun,
>
> Brooke Clarke
> http://www.PRC68.com
> http://www.end2partygovernment.com/2012Issues.html
>
>
>
>
> ------------------------------
>
> Message: 3
> Date: Sun, 07 Apr 2013 13:55:13 -0700
> From: WB6BNQ <wb6bnq at cox.net>
> To: Discussion of precise time and frequency measurement
> <time-nuts at febo.com>
> Subject: Re: [time-nuts] Changing FE-5650A frequency?
> Message-ID: <5161DD31.1AB6258 at cox.net>
> Content-Type: text/plain; charset=us-ascii
>
> Hi Alec,
>
> I am going to agree with Robert (G8RPI) on his assessment, particularly as 
> the dip switches are clearly visible in one of the pictures.  Although I 
> wonder why Robert feels unfortunate about the [ two chip DDS arrangement ] 
> ?
>
> It matters not the number of chips that make up the DDS.  Why ?  Because 
> the actual physics package and its electronics has nothing to do with the 
> DDS in the older designs.  That is, the signal output of the physics 
> package is a fixed frequency  (around 50.255 MHz) that you could capture 
> and feed to a more modern DDS if necessary as replacement of the old one 
> is probably not going to happen.  However, if it is working then once you 
> get to a frequency you need you probably not touch it again.  So no loss 
> there.
>
> As for calibration, there is a hole on one side of the can that has a 
> multi-turn pot that adjusts the "C-field" current.  The C-field is a very 
> fine frequency adjustment.  You first adjust the C-field pot to its lowest 
> setting (as in frequency), then set the DDS to the closest frequency on 
> downside of where you want to go and then adjust the C-field pot to come 
> up on to the frequency.  The C-field pot is a really fine adjustment, so 
> we are talking very small movement that will require patience, a better 
> reference and at least a
> oscilloscope to watch the drift rate over a very long time. A truly time 
> consuming experience.
> However, if you leave that C-field pot alone, you will most probably be 
> inside 1 part in 10 to the minus 9th.
>
> The most recent designs have the DDS in the control loop for the physics 
> package.  In the new internal design in order to change frequencies you 
> need to actually change the BASE crystal frequency, the DDS and the 
> firmware to get a new output frequency.  So basically a real pain in the 
> ass.
>
> As for the foam that is sandwiched in between the boards, I agree with 
> Robert that it is for temperature stability in varying environments.  If 
> the unit is kept in a normal room all the time then the foam is not a 
> concern and could be carefully cleaned off.  There is some other 
> components that have white stuff that looks more like an RTV type 
> substance used to hold down a component like what is seen in photograph 
> IMG_20130407_102937.jpg at the two toroids,  That I would leave alone.
>
> Your finding the 12+ MHz just confirms that the design is very similar to 
> that described in the FTP file I provided.  Make sure you record the 
> switch settings before you change them so you can return to a reference 
> point.
>
> Although you did not indicate, I assume you downloaded the FTP file ? 
> Please let me know so i can reduce the storage level as it is not my site 
> although I have use of it on a short term basis.
>
> Thank you,
>
> Bill....WB6BNQ
>
> Alexander Wright wrote:
>
>> On 07/04/13 17:56, Robert Atkinson wrote:
>> > Hi Alex,
>> > These units were used as timing references for secure communication 
>> > systems (Havequick). see ebay item 130832014630. Unfortunatly they are 
>> > an older design with a two chip DDS. The other problem is that the "M" 
>> > designation is for military and means they have been partially 
>> > encapsulated with polyurethene foam. You can cut it away but it is very 
>> > easy to damage the PCB. Frequency setting is by DIP switches (under the 
>> > foam) allowing full range of frequency selection. However the output 
>> > filter is narrow so you can't go far from 800kHz.
>> > Did you buy all seven?
>> >
>> > Robert G8RPI.
>> >
>> >
>> Robert,
>> Thanks for the info! I bought one of these wondering what they were,
>> took it apart and found the rubidium clock and figured it must be worth
>> something (more than the 15 quid he was asking) so I bought the remaining 
>> 6!
>>
>> I've taken the foam off the top PCB and i've found that there's a
>> 12.8MHz signal being produced which is then being divided down with an
>> 800kHz logic chip. I should imagine the filter must be on the circuit
>> board below? I might try changing the frequency
>> of the DDS chip, removing the frequency divider and tinkering with the
>> output filter. Do you have any info on what sort of filter I should
>> expect to find?
>>
>> Thanks,
>> Alec M0TEI
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>
> ------------------------------
>
> Message: 4
> Date: Mon, 08 Apr 2013 15:54:22 +0200
> From: Achim Vollhardt <avollhar at physik.uzh.ch>
> To: time-nuts at febo.com
> Subject: Re: [time-nuts] Lady Heather
> Message-ID: <5162CC0E.3040903 at physik.uzh.ch>
> Content-Type: text/plain; charset=ISO-8859-1; format=flowed
>
> Hi Mike,
> try typing:
>
> s: Survey
> a: Antenna
> s: Signal
>
>
> in that sequence from main menu.
>
> 73s Achim, DH2VA
>
>
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