[time-nuts] Frequency Electronics, Inc. FE-405B Oscillator Availability

Bruce Griffiths bruce.griffiths at xtra.co.nz
Thu Dec 10 20:04:30 EST 2015

Its not too difficult to setup a low noise regenerative divider  that will produce a 10 Mhz output from a 15MHz input.

    On Friday, 11 December 2015 2:01 PM, Skip Withrow <skip.withrow at gmail.com> wrote:

 Hello Time-Nuts,

RDR Electronics has a limited supply of FEI FE-405B OCXO oscillators with
digital  frequency control available.  These are very good crystal
oscillators that are generally BELOW 1x10E-12 from 1 to 1000 seconds (some
approaching a couple of parts in 10E-13).  The mediocre ones are in the
1x10E-11 to 1x10E-12 range for 1 to 1000 seconds (still very good).  In
addition, these units have digital tuning via a serial port that has a
resolution of 1.05x10E-14 (no DACs involved, it’s done with a DDS)!  These
units have a DB-9 connector that is compatible with the FE-5680A and
FE-5650A rubidium units (no LOCK or VCXO signal, of course).

That’s most of the good news, the bad news is that these are 15MHz
oscillators and cannot be changed.  There is a 15MHz PLL and crystal filter
that are the two largest hurdles.  The ovenized oscillator in the unit is
at 5MHz, but it is buried deep below all of the rest of the goodies that
make these interesting.

You can check out lots of FE-405B data on Tom van Baak’s website at
http://www.leapsecond.com/pages/fe405/ .  There are some slides at the end
of all the graphs.  You can check out pictures of the unit at:






The jumping around has been solved.  It is caused by uP temperature
compensation that changes the DDS value based upon the oven heater current.
This input to the uP can be grounded which drives the offset to the max
value and it stays there.  This is absolutely what you would want for a
GPSDO so that you don’t have your control loop fighting the temperature
compensation.  My thinking is that this is what you would want for a
reference oscillator as well, but we have left a few units unmodified.

After running for a while the aging of these units gets down in the
1x10E-12/day range.

In addition, we have set these units so they are reasonably on frequency
(parts in 10E-10) with a 00 00 00 00 control value (same commands as the
FE-5680 and FE-5650).  The range of control values on the FE-405B is F7 33
33 34 to 08 CC CC CC.

We have a VERY limited supply that have been characterized by Corby Dawson
and his H-maser (thanks) and ADEV plot will be sent with the unit.  They
fall into three general groups:

  1. Temperature compensation disabled, great ADEV (1x10E-12 to 1x10E-13
  2. Temperature compensation disabled, good ADEV (1x10E-11 to 1x10E-12)
  3. Temperature compensation intact, great ADEV (1x10E-12 to 1x10E-13

I would like to offer these up to the time-nuts community.  Asking $200 for
Group 1 and 3 units, $150 for Group 2 units.  Postage to the US is $7.10,
we will ship international – postage is $26.50.  I can send a copy of the
ADEV plot for the unit you would receive via email before you decide to
purchase if desired.  Please send email to skip at rdrelectronics.com.

Sorry for the long post, and the commercial nature (but it is exclusive to
time-nuts at this point).


Skip Withrow

RDR Electronics, Inc.

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