[time-nuts] Controlling FEI 5680A

[EWKehren at aol.com]

I have no expertise when it comes to filter design or programming PIC's or  
other micro controllers. But I know what works for me. For 11 years I have 
been  using Shera controllers with very good results. (I still have some new 
assembled  extra A&A boards, if any one is interested, please contact me 
off list) Over  the years I have made hardware work around's and made my own 
boards ending up  with 120 and 240 samples and 100 MHz clock in stead of 24 
MHz. Over time chips  are harder to get. The solution is an Altera MAX 3000 
gate array and that input  circuit can be implemented on a $ 2  100 MHz 
version or $ 5   200  MHz version using either a 100 MHz or 200 MHz clock. That 
circuit works with the  present Shera PIC but that is a 28 pin $ 4   device. 
Since in  this application the controller does not have  to be all things 
for all  devices it would make sense to use a PIC16F688  or any other 14 pin 
device.  Brooks, if so inclined could do it or some one else if he would 
allow it. For my  personal use I can live with the present PIC and the work 
around's that I have  incorporated. The result is a $ 35 solution using an 
analog output.
 I have laid out a board that once I know the pin assignments I will  
gladly have made and furnish with G/A to the individual that will do the design.  
An analog portion with opto couplers is also included.
The Gate Array solution is thanks to Juerg Koegel, a list member that has  
worked with me on the Dual Mixer. The analog portion has been fully 
functioning  for two years but I had not found some one to test the counter part 
with  Ulrich's or Stable 32 plotter. Thanks to Juerg that is now done. Found 
out that  I had made a mistake in my thought process but we now have a fully 
functioning  counter with nice plotting results. Again thanks to Juerg a G/A 
have replaced  logic chips that soon may  be hard to get. The first boards 
are in and test  results will be available soon. This is a 2 channel counter 
in the ping pong  mode that can be switched from period to phase allowing 
set up with out the use  of any other counter. 1 E-15 and 5 E-16 will be 
available.
Juerg is also helping me with the what I call the Austron circuit allowing  
1E-12 resolution in one second. The first unit was a direct copy of the  
Austron 2110 circuit using a dual stage Xtal filter the next one will use a 
DDS  for the offset. This will happen after the 5 channel counter test which 
will  allow cross correlation and 3 corner hat testing. Board is laid and 
G/A's  designed but we are waiting till the 2 channel is fully tested.
Juerg is also working on an interface board that will have a LCD display  
and USB memory stick interface. That allows the D/M be operated independent 
of a  PC with plotting done by the PC after the test run, transferring the 
data with  the USB stick. RS232 or blue tooth is also an option. Richard 
McCorkle was key  in the design of the counters, thanks to his PIC expertise. 
With out him the low  cost solution would not have been possible. 
This work will be followed by the Austron circuit and hopefully by a low  
cost control loop.
 
Questions have been asked as to what I use for frequency testing.  Because 
of my work on signal generators I rely heavily on a HP 5345A counter  that 
gives me 40 GHz measurement capability. It with its internal 500MHz  
reciprocal counting capability injecting noise into the 500 MHz it allows me 1 E  
-12 over 1000 seconds. Combined with the Tracor 527E I can get 1 E-16 with the 
 last two digits of not much use. I like the 1000 sec gate time since it in 
 effect does some averaging. My testing of the 56680A is done with the 5345 
with  out the Tracor.
I also use the Austron 2110 for longer time testing. In the past it was  
tied to Loran C now to Tbolt.
As frequency sources I use a HP 5061 B, HP 5062 C a FRK-H using a Shera  
controller and Tbolt. The FRK is presently out on loan. In the past I used a 
GPS  receiver, now I use the Tbolt. The plan is to have it tested against a  
Maser.
I hope this answers a lot of questions. What is needed is that some one  
steps up to the plate and does the controller. To me the appeal is the $15  
solution. 
Bert Kehren