[time-nuts] DMTD 31 March 2010

Brian Kirby kilodelta4foxmike at gmail.com
Wed Mar 31 18:15:58 UTC 2010


I was a little confused last night - burning my fuse at both ends.  
Today, I made some changes, and I have attached a new drawing of what I 
am working with.

When I built the board this morning, the capacitance load on the mixer 
was not square (from last nights values).  I suspect because it was not 
hooked up to circuitry and I forget a scope probe also has capacitance.  
So this morning, I played on a active/hot board.  With the components 
listed on the front end of the LT1028 (see the attached drawing), I am 
able to get a fair , rounded on the edges , square wave.  I'll shoot a 
picture later.  I also lowered the series resistance.

A 30 minute quick test of the board, a "pseudo" test of the noise floor, 
with the same 10 Mhz inputs and a 100 hertz beat, is showing TI data in 
the 40 nanosecond range.

Plotter reports; (Allan Var)    {Plotter is a free variance program - 
Thanks to Ulrich Bangert DF6JB}
0.01 second = 2.1x10-12
0.1 second = 2.1x10-13
1 second =  2.2x10-14
10 second = 2.2x10-15
100 second  looks like its going to be 2x10-16.

A short description of the system; I use a HP5065A rubidium as the 
reference oscillator.  It feeds a HP5087A distribution amplifier.  A 10 
Mhz output is routed to a HP355A attenuator and routed to one RF port of 
the DMTD system.  A Wavetek 5120A synthesizer is used to generate the 
offset/beat at 9.9999 Mhz.  The Wavetek is slaved to the 5065A.  The 
output of the Wavetek is routed to a TAPR TADD1 distribution amplifier.  
Two outputs are routed to the two LO input ports of the DMTD system.

The Time Interval counter is a HP5370B, I have a ProLogix USB-GPIB 
adapter on it and its set to talk.  I use an older 500 Mhz Pentium II 
computer that has Windows 2000 on it (a triple boot machine for running 
older programs - also boots NT4 and DOS).  I use John Miles, KE5FX, 
ProLogix GPIB Configurator program to set up the adapter, and use 
Windows HyperTerm to record the data.

I am going to let the test run until this evening, and then, takes some 
pictures, and then rerun the test at 10 hertz beat.

After some testing, it will be on to designing the zero crossing 
amplifiers/limiters next....

Brian - KD4FM



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