[time-nuts] WWV / WWVH / WWVB
Brooke Clarke
brooke at pacific.net
Thu Nov 20 20:14:43 UTC 2008
Hi Brad:
To get the best s/n radio you need to have good narrow filters. The NRD-545
uses DSP for the IF filters and so can be adjusted to a 10 Hz bandwidth. This
is the lowest IF bandwidth I know of in any HF receiver including the high end
and military models. The only things with narrower bandwidths are the
HP/Agilent 4395A in spectrum analyzer mode where there is a 1 Hz bandwidth or
the PC sound card spectrum analyzers where you can get sub Hertz bandwidths.
http://www.prc68.com/I/NRD545.shtml
http://www.prc68.com/I/4395A.shtml#SA
The 114BR Time Comparator was used with WWV and WWVH in conjunction with a
receiver and scope. http://www.prc68.com/I/TF_rack.html
You could duplicate the function of the HP 114 using a variable time delay for
phase comparison.
The antenna is about as important as the receiver for HF and LF signals. For
HF I really like the B&W Terminated Folded dipoles. Chirp receiver testing
showed them to be far superior to every thing else.
http://www.prc68.com/I/RCS-5A.shtml#Ant
The trick to getting a PIC to decode the subcarrier data would be best done by
audio filtering prior to amplitude detection. I haven't worked with the DSPics
but that would allow doing better filtering in the PIC.
http://www.prc68.com/I/TF_rack.html
For WWVB the amplitude changes but the carrier is always there. Starting Jan 1
2006 the modulation depth was changed from 10 to 17 dB, see:
http://tf.nist.gov/timefreq/general/pdf/2139.pdf
It's very important that you filter out close by RF signals. Here is a 0 to
200 kHz spectrum plot: http://www.prc68.com/I/Spec_0002.shtml
you can see that there are plenty of signals there.
Have Fun,
Brooke Clarke
http://www.prc68.com
Brad Stockdale wrote:
> Hello all,
>
> Thank you to everyone that has helped (and some that continue to
> help) me with my GPSDO equipment post... I've got a few leads out
> there and hopefully I'll be able to get ahold of some of these units
> soon... I really am looking forward to getting to work with some other GPSDO's.
>
> Anyway, on to the reason for this post... I'd like to get some
> receivers so I can HEAR and USE the WWVB, WWV, and WWVH signals... I
> know that HEARING them may not be a 'normal' request, but I just
> would like to monitor the audio as well as being able to decode the signals...
>
> I guess the first thing to take care of is receiving the signals.
> Can anyone recommend decent receivers for these stations? I guess the
> list of frequencies would be:
>
> o WWVB = 60 KHz
> o WWV = 2.5 MHz, 5 MHz, 10 MHz, 15 MHz, or 20 MHz
> o WWVH = 2.5 MHz, 5 MHz, 10 MHz, or 15 MHz
>
> Hmm, I just noticed that WWV and WWVH overlap... How in the heck
> do you differentiate between the two stations if they broadcast on
> all the same channels?
>
> Anyway, I wouldn't mind a kit type of project that would let me
> receive these signals... Maybe I'll check out Ramsey Electronics,
> Rainbow Kits, Velleman, et al. Surely one of them has kits for these
> broadcast ranges.
>
> Can anyone suggest a kit, or project listed online with
> schematics and parts lists, or I guess even reasonably priced commercial units?
>
> If I can't get radios that have built in decoders for these
> stations, I'd be happy just receiving their audio and then trying to
> build my own decoder using a PIC or something...
>
> Thanks for any advice.
>
> Brad
>
>
>
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