[time-nuts] FE5680 GPS Disciplined Controller
vk3yba at gmail.com
Wed Jun 18 22:04:47 EDT 2014
Please count me in on this project. A mini kit would be fine at almost
On 19/06/2014 4:49 AM, EWKehren at aol.com wrote:
> FE5680 GPS Disciplined Controller
> With all the FE 5680 rubidium oscillators being used as door stops out
> there some of us decided to develop a GPSDO for it. The main question we have:
> Is there sufficient interest among time nuts for a discipline controller
> for the FE5680 to make it available? Looking at the postings over the last
> two years I am not so sure.
> The construction and preliminary testing of a Brooks Shera style GPS
> discipline controller for the later version (6.81e-13 resolution) of the FE5680
> has been completed. We are trying to determine the number of people that
> would be interested in obtaining an FE5680 discipline controller (if there is
> sufficient interest about $45 a kit shipping included, $75 for an
> assembled and tested board, international orders for an additional $5) when it is
> We are also looking for three Beta testers that would be willing to
> purchase, assemble, and test our Beta release controller kit with their own
> FE5680A and GPS receiver or Tbolt and provide feedback. Please send an email to
> _EWKehren at aol.com_ (mailto:EWKehren at aol.com) Subject Time-Nuts FE 5680A,
> if you would be interested in being one of the three Beta testers. A key
> requirement is the willingness to get to it right away, the board assembly
> takes about 30 minutes. Instrumentation to measure results is also a
> requirement. We obtained impressive results using a cheap ublox 6M receiver.
> The FE5680 GPS discipline controller is a small (2" x 2") board using 8
> DIP's and 1 SOT23-5 package powered by +5v with 0.1" headers for all inputs
> and outputs. Our plan is to have the kit supplier solder in the only SMD
> device on the board. A GPS receiver 1PPS and 10 MHz sine from the FE5680
> feed the board with two 9600 baud serial ports sending TTL level tuning
> commands to the FE5680 and receiving commands from and sending status data to a
> PC for data logging and system control via a simple terminal program.
> In the chip count are two opto couplers that allow the use of isolated TTL
> to USB conversion. These USB adapters are readily available and furnish
> the 5 V necessary for the secondary of the opto circuit. An option is to not
> use the opto couplers and send the PIC TTL level RX and TX into a TTL to
> RS232 adapter. Another option is to use a TTL to RS232 converter after the
> opto couplers but then an external 5 V source would have to be supplied for
> the opto couplers.
> As I mentioned before to get best performance from the FE5680 temperature
> control is a must and after much fan and metal work I realized that a Lap
> Top heat pipe is the easiest lowest cost solution. Comments appreciated. As
> an alternative the temperature correction needs to be disabled. Otherwise
> two control loops fight each other. If you look close on page 7 of the
> brochure temperature stability from --10 to +60 C looks good but a closer look
> and you see 4 E-11 changes over small temperature changes in the -10 to 60
> C range. Extensive analysis has been done on the FE 5680 A and maybe some
> one can tackle that problem. Please look at what N5TNL did. It is attached
> and click on his link. The FE 5680A does have a 4 channel MAX 1246 ADC and
> most likely it is used to monitor temperature.
> Also mentioned before the FE 5680 output is not the cleanest, I did
> observe it and some one posted the attached. I apologize but my records do not
> show who did, so if you posted the data please come forward. For serious
> applications where you are using it as your main reference a clean up like the
> Morion MV89 or HP 10811 should be considered.
> This addition is not required for beta tests but temperature control will
> I am also enclosing the express PCB layout, be free to use it but it would
> be more economical to do a group buy if there is enough interest and some
> one steps up to kit.
> Bert Kehren
> To not exceed the attachment limit the plot will be a separate posting
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