[time-nuts] Dual Mixer update
EWKehren at aol.com
EWKehren at aol.com
Sun Feb 20 12:26:00 UTC 2011
It is close to 18 month now that I first proposed a D/M for $200. Thanks to
the help of Corby, Richard, Brian, Bob and Hubert I think it is very close
to final release. The delay is mainly due to testing, not by the five
mentioned above but by others, that did get kits under the condition that they
would perform complete tests.
Corby focused on the Mixer board with excellent results and recommendations
with the final product now using AD 8007 and AD 8008 amplifiers for better
isolation. 1 E-13 at one second has been measured. To refresh every ones
memory it is a direct copy of the original NBS design with newer components
and opto coupler in stead of transformer.
The counter went through two iterations and Richard was key with design
support and PIC programming. A 100 MHz VCO/PLL was added in such a way that
the 5/10 MHz reference can be used for counter frequency generation.
Hubert finally tested the complete system and that is why I am comfortable
Why did I not do the complete unit testing, my computer skills are lacking!
Depending on the user the counter can get its power from the PC or the +-
12 Volt needed by the D/M. When powered by the +-12 the opto Isolators can
be left out since the counter in turn is opto isolated on the output.
Counter talks to RS232 and USB. The counter in the one second mode has a
resolution of 1E-15. Obviously external counters can be used but at a total cost of
$ 30 keeping ones counter free for other tasks would make sense.
Cost of the system is mainly driven by board cost but with 20 board sets
the goal of $200 is attainable. Could not stay away from SMD parts because
some circuits are not available in DIL but there are only five on the D/M
and four on the counter. All but one are easy, the only challenge is the ADF
4001 PLL but doable.
All info will be available to every one and I have no desire to get into
the kit business but if only a small group is interested I will order boards
and critical components.
Right now I am looking for two time nuts that want to build a complete unit
and run tests with specific focus on the counter USB/R232 interface and
adaptation of presently available plotting software. I would help with a
parts kit at cost. Please contact me direct and please only if you are willing
and able to get on it right now, the project could have been done eight
month ago if testing would have been done as promised.
On a related subject Hubert and I are working on a slightly changed Austron
circuit that I previously posted, that will allow measuring delta between
two frequencies to 1 E-14 in one second, did get boards and will keep you
updated on progress.
Bert Kehren Miami
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