[time-nuts] WWVB: measuring local 60 KHz noise

Bob kb8tq kb8tq at n1k.org
Sat May 5 11:49:10 EDT 2018


If you want delay ( hardware delay and not propagation), calibrating a SDR should not
be to nutty. Some boards ( the Lime SDR comes to mind) will generate a signal as well
as receive one. That could be piped into a scope to make the measurement fairly
easy. Once you know what is going into the receiver and what is coming out, it’s just 
twiddling the knobs ….


> On May 5, 2018, at 5:50 AM, Dana Whitlow <k8yumdoober at gmail.com> wrote:
> Hal,
> Some SDRs can tune that low and should provide a means to determine
> if noise is really the problem as well as give some clues as to the
> character
> of said noise.  But they are much less likely to help with delay
> determination,
> unless you can figure out a practical way to ascertain the latency in both
> the
> SDR's HW and its SW.  The latter component will also vary considerable
> depending on what computer you are using with the SDR, as well as with
> random variations due to the vagrancy of typical operating systems.
> I recently did a crude delay estimation for WWV (not WWVB) using my
> Sony ICF-2010 receiver, a 2-channel DSO, and an Adafruit "Ultimate GPS"
> module's PPS output.  The combined (receiver + propagation) delay was
> very close to 5 msec in Kerrville, TX.  The precision was mostly limited by
> my inability to decide precisely where each WWV tick started on the 'scope's
> display due to distortion arising from multipath and the receiver's
> filters.
> The actual received waveform varied considerably from second to second.
> Dana
> On Sat, May 5, 2018 at 3:08 AM, Hal Murray <hmurray at megapathdsl.net> wrote:
>> Review/background:  I have an UltraLink 333 WWVB receiver.  It didn't
>> work.
>> Several weeks ago. a discussion here mentioned that the phone cable
>> between
>> the main box and antenna needs to be straight through rather than the
>> typical
>> reversed.  That was my problem.  With the correct cable, the meter shows
>> signal and bounces around such that with practice, I could probably read
>> the
>> bit pattern.  But it didn't lock up.
>> That was several weeks ago.  I left it running.  When I looked last night,
>> it
>> had figured out that it is 2018.  I wasn't watching or monitoring, so I
>> don't
>> know how long it took.
>> I assume the problem is noise.  Is there any simple way to measure the
>> noise
>> around 60 KHz?  How about not so simple?
>> Extra credit for a way that others nuts can reproduce so we can compare
>> the
>> noise at my location with other locations.
>> Can any audio cards be pushed that high?  I see sample rates of 192K, but
>> I
>> don't know if that is useful.
>> I'd also like to measure the propagation delays on WWV so a setup for HF
>> that
>> also works down to 60 KHz would be interesting.
>> ----------
>> The UltraLink documentation says the display has a slot for a C or H.  The
>> C is for Colorado and the H is for Hawaii.  Did WWVH have a low frequency
>> transmitter many years ago?  The NIST history of WWVH doesn't mention it.
>> My guess is a cut+paste from a version that listened to WWV/WWVH.
>> --
>> These are my opinions.  I hate spam.
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