[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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