[time-nuts] FE5680 GPS Disciplined Controller

Ernie Peres ernieperes at aol.com
Wed Jun 18 15:40:03 EDT 2014


 I am interested a complete KIT  ready made and tested. Also if this version is not available then just the simple KIT including PCB...parts and so on. PIC programmed.

Rgds  Ernie.

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Subject: time-nuts Digest, Vol 119, Issue 25

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oday's Topics:
   1. FE5680 GPS Disciplined Controller (EWKehren at aol.com)

Message: 1
ate: Wed, 18 Jun 2014 14:49:02 -0400 (EDT)
rom: EWKehren at aol.com
o: time-nuts at febo.com
ubject: [time-nuts] FE5680 GPS Disciplined Controller
essage-ID: <59d7b.5d95a57a.40d3391d at aol.com>
ontent-Type: text/plain; charset="utf-8"
E5680 GPS Disciplined  Controller
ith all the FE  5680 rubidium oscillators being used as door stops out 
here some of us decided  to develop a GPSDO for it. The main question we have: 
s there sufficient  interest among time nuts for a discipline controller 
or the FE5680 to make it  available? Looking at the postings over the last 
wo years I am not so  sure.
he  construction and preliminary testing of a Brooks Shera style GPS 
iscipline  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 
ould be  interested in obtaining an FE5680 discipline controller (if there is 
ufficient  interest about $45 a kit shipping included, $75 for an 
ssembled and tested  board, international orders for an additional $5) when it 
e are also looking for three Beta  testers that would be willing to 
urchase, assemble, and test our Beta release  controller kit with their own 
E5680A 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, 
f you would be interested in being one of the three  Beta testers. A key 
equirement is the willingness to get to it right away, the  board assembly 
akes about 30 minutes. Instrumentation to measure results is  also a 
equirement. We obtained impressive results using a cheap ublox 6M  receiver.
The  FE5680 GPS discipline controller is a small (2? x 2?) board using 8 
IP?s and 1  SOT23-5 package powered by +5v with 0.1? headers for all inputs 
nd outputs. Our  plan is to have the kit supplier solder in the only SMD 
evice on the board. A  GPS receiver 1PPS and 10 MHz sine from the FE5680 
eed the board with two 9600  baud serial ports sending TTL level tuning 
ommands 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.  
n the chip count are  two opto couplers that allow the use of isolated TTL 
o USB conversion. These  USB adapters are readily available and furnish 
he 5 V necessary for the  secondary of the opto circuit. An option is to not 
se the opto couplers and  send the PIC TTL level RX and TX into a TTL to 
S232 adapter. Another option is  to use a TTL to RS232 converter after the 
pto couplers but then an external 5 V  source would have to be supplied for 
he opto couplers.  
s I  mentioned before to get best performance from the FE5680 temperature 
ontrol is  a must and after much fan and metal work I realized that a Lap 
op heat pipe is  the easiest lowest cost solution. Comments appreciated. As 
n alternative the  temperature correction needs to be disabled.  Otherwise 
wo control loops fight each  other.  If you look close on page 7  of the 
rochure temperature stability from ?10 to +60 C looks good but a closer  look 
nd you see 4 E-11 changes over small temperature changes in the -10 to 60  
 range. Extensive analysis has been done on the FE 5680 A and maybe some 
ne  can tackle that problem. Please look at what N5TNL did. It is attached 
nd click  on his link. The FE 5680A does have a 4 channel MAX 1246 ADC and 
ost likely it  is used to monitor temperature. 
lso  mentioned before the FE 5680 output is not the cleanest, I did 
bserve it and  some one posted the attached. I apologize but my records do not 
how who did, so  if you posted the data please come forward. For serious 
pplications where you  are using it as your main reference a clean up like the 
orion MV89 or HP 10811  should be considered. 
his  addition is not required for beta tests but temperature control will  
 am also  enclosing the express PCB layout, be free to use it but it would 
e more  economical to do a group buy if there is enough interest and some 
ne steps up  to kit. 
ert  Kehren 
o  not exceed the attachment limit the plot will be a separate  posting 

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