[time-nuts] simple phase finder

[Brian Lloyd]

On Wed, Dec 5, 2018 at 8:52 AM jimlux <jimlux at earthlink.net> wrote:

> On 12/5/18 6:32 AM, Bob kb8tq wrote:
> > Hi
> >
> >> On Dec 5, 2018, at 8:45 AM, jimlux <jimlux at earthlink.net> wrote:
> >>
> >> On 12/5/18 5:39 AM, Poul-Henning Kamp wrote:
> >>> --------
> >>> In message <4a8ff8d6-70b2-782e-cb79-21c7e9a49649 at earthlink.net>,
> jimlux writes:
> >>>> If I were decoding WWVB to start, I'd break my samples up into 0.1
> >>>> second or 0.5 second chunks and process them to see what the carrier
> >>>> phase is.
> >>> With stable signals like this, it is a bad idea to chop them up,
> >>> in particular if your ADC runs from a good stable frequency.
> >>
> >> True enough - this was just to get started.
> >>
> >>> Instead continuously average the square of the signal into a 1
> >>> second long circular buffer.
> >>> Then multiply/sum that buffer with a 120kHz sine and cosine to find
> >>> the phase angle.
> >>
> >> yes.. assuming your ADC is running off a sufficiently stable source.  I
> was thinking about a very low cost implementation where the ADC is running
> off a not very wonderful microcontroller clock.
>

Are you aware that the KiwiSDR receivers are locked to GPS and time-stamp
their samples? Some people are playing with TDoA location of HF emitters
using multiple KiwiSDRs out there.

>
> > A stable clock probably is a pretty good bet on a “Time Nut” grade
> design. Indeed one objective might be to ultimately
> > read out the phase directly WRT that reference . Some sort of PPS tick
> likely would get into all this as well.
>

Yeah, do more research into the KiwiSDR.

>
> >
>
>
> I was thinking more about "can you receive it with a SDR implementation
> for <$50 and minimal heating of the soldering iron" without worrying too
> much about measuring small phase shifts.
>
> Once you've got to that - then you've got a basis for further improvements.
>
> I'll try the RTL-SDR with a non-active antenna on Friday and see what I
> can see here in Southern California.  I know my old style "atomic" clock
> does see the signal sometimes, so I can grab some sample when the clock
> says it's live.
>
>
> If anyone has a suggestion for an off the shelf active antenna that's
> orderable and receivable by Friday, I'd love to hear it.  There's 3 or 4
> of them I've seen (Clifford labs, DX Engineering has one, I'm sure MFJ
> has one)
>

I have the PixelSat loop (now sold by DX Engineering) and it works great at
60kHz. I hear WWVB 7x24 in San Antonio. MFJ has a cheaper version that I've
heard works OK.

I have my loop driving my KiwiSDR. I haven't made it public (yet). I hear
WWVB with it just peachy all the time.


> Why available by Friday? I'm going to be really busy starting next week
> for a month commissioning a satellite launching next week, so this
> weekend is my last opportunity to fool with actual technology.
>

DX Engineering or MFJ. You might find that HRO has one or the other in
stock. Don't they have a store in Las Vegas, not too far from you? UPS
ground should get to you in a day.

-- 



Brian Lloyd
706 Flightline
Spring Branch, TX 78070
brian at lloyd.aero
+1.210.802-8FLY (1.210.802-8359)