Please count me in on this project. A mini kit would be fine at almost
any cost.
Regards
Max
On 19/06/2014 4:49 AM, [email protected] 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
released.
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
[email protected]_ (mailto:[email protected]) 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
help.
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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