[time-nuts] FE 405/5680/5650 caution !!!!

EWKehren at aol.com EWKehren at aol.com
Sat Dec 12 13:43:25 EST 2015

Shortly after joining time-nuts on Corby's recommendation I announced that  
I wanted to build a complete Dual Mixer for less than $ 200. Richard 
McCorkle  offered to help me with the code for the counters. After completion we 
started  talking about GPSDO's which I had previously worked with Brooks 
Shera on. We did  an extensive methodical review of the system and discovered 
serious problems  with the the AD1861  when used in a filter application. We 
tested many D/As  and switched to the LTC1655. Explored dithering.
During that work a German friend that I work with on a different subject  
made me aware of the FE5680. At the price I bought a couple and was surprised 
at  its performance.  Though they had been in Europe for a couple of years 
I  had not seen any thing on time-nuts. I published my observations. At the 
same  time we started work on a digital controller Richard the code and the 
rest of us  testing and analysis. A year in to the program I discovered the 
FE 405 on ebay  and bought 4 for the team. Early on I noticed outstanding 
performance that was  later confirmed by Tom. Focus was shifted to the 405. 
After many iterations we now have a Universal GPSDO based on which PIC we  
insert.  Works on the FE405, Skip's 5650 and the 5680 that every body  
bought out of China. Some time nuts have run units for over a year and I feel  
comfortable to have Cash build, test and sell the units soon. Units he  build  
are presently being tested. We are also assembling a documentation  package 
that will be on his web site.
Depending what the interest is there also will be an auxiliary board for  
the 405 with a divider and output filter for 5 MHz, DC/DC converter, 
regulators  and a PIC for display purposes. This board will not be assembled but 
comes with  two MC output transformers since small purchase will not be 
economical. All  other parts will be readily available.
An analog temperature control board, board only will also be  available. 
All boards a 5 X 5 cm and stack able.
There was talk about a digital fan control hope some one will step up to  
the plate.
Hope this answers your question.
Bert Kehren
In a message dated 12/12/2015 11:00:46 A.M. Eastern Standard Time,  
jsrobbins at earthlink.net writes:


For those of us who are not familiar with your work,  but who have 
purchased one of Skip's FE 405s, could you summarize what work  you and your group 
have done on the "FE 405/5680/5650"?

You say "Cash  Olsen will be responsible for the sale of assembled and 
tested units."   What assembled and tested 
units are you referring to?

Many  thanks.

Jim Robbins
Can be directly emailed at call  @arrl.net

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