[time-nuts] NAA experiments as a reference

paul swed paulswedb at gmail.com
Sun Sep 14 21:51:23 EDT 2014

David thanks what you say seems to be true. I could see the stable 100 Hz
and the 200 Hz was a typical 2 X lissajuo pattern within the 100 Hz pattern.
>From your comments then I speculate the following from Tracor.
They used a LO 100 Hz below because the synthesizer was reasonable to
build. Adding the 50 Hz would have been messy at that time. They have a PLL
runing at 10 X the final LO frequency and it steps in 100 hz increments
after its been divided.
The LO is at 23.9 KHz and the demod out was 50 Hz and 150 Hz that was
doubled to 100 and 300 Hz. But the signal passed through a 100 Hz BPF
leaving just the 100 Hz. I should be able to see that 100 Hz against the
100 Hz reference but its not nearly as nice looking as the -150 Hz LO.

On Sun, Sep 14, 2014 at 2:52 PM, David I. Emery <die at dieconsulting.com>

> On Sun, Sep 14, 2014 at 10:20:48AM -0400, paul swed wrote:
> > I still do not see why if I offset the LO to -150 hz I get a useful
> display
> > to judge timing. I am using the lissajous method.
>         Consider that with the LO offset 150 Hz you will have a 100 Hz
> beat note with the mark tone and a 200 hz beat note with the space
> tone - more or less exactly right on if the MSK signal carrier is right
> on (which it is) and the signal is true MSK (which is is) and the 150
> Hz LO is nearly right on (which it presumably is).
>         And the 200 Hz and 100 Hz are of course related and coherent
> with each other (the phase of the mark and space tones is precisely
> related to each other because of the nature of true MSK).
>         This means the resultant waveform should be stable seen in
> a sweep triggered by your local clock at 100 Hz and also in a lissajous
> pattern with the LO.
> --
>   Dave Emery N1PRE/AE, die at dieconsulting.com  DIE Consulting, Weston,
> Mass 02493
> "An empty zombie mind with a forlorn barely readable weatherbeaten
> 'For Rent' sign still vainly flapping outside on the weed encrusted pole -
> in
> celebration of what could have been, but wasn't and is not to be now
> either."
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