Re: wwv receiver

From: Joe McElvenney (ximac_at_btinternet.com)
Date: 08/15/04 

Date: Sun, 15 Aug 2004 16:51:54 +0000 (UTC)

Hi,

   Here in the UK, I have often wondered about making a frequency
standard using the signal from MSF in Rugby (which like WWVB is
on 60kHz). The main problem using conventional circuitry would
appear to be that these time signal carriers are interrupted at
intervals and so would require very long time-constants to fill
the gaps. Further, to obtain a clean signal from off-air signals
such as these would require some regeneration - usually in the
form of a phase-locked loop.
   
   One thought did occur to me once though and that was to use
the mechanism from a cheap 'radio-controlled' clock, which must
put out a once-a-second current pulse and so could be used, á la
Brooks Shera - W5OJM, to discipline a standard. Unfortunately I
found out that they sync-up only every so often which quickly put
the kibosh on that idea.
   
   I haven't tried a standard derived from a signal using an
interrupted carrier but I have done this successfully with an AM
broadcast station such as the BBC's long-wave transmitter on 198
kHz. I wonder then if there are similar local stations in the
States that might also be locked to a national standard. Even one
that is not so may perhaps use a GPS-locked transmitter drive and
could be employed. BTW, the colour-burst signal on networked TV
transmitters is often traceable to a national standard.
   
   On the AM-band a simple TRF in front of a hard limiter
suffices for the receiver (I used a single series resonant xtal
to strip the sidebands away) with the resultant divided down to
feed a PLL together with another input derived from a 10MHz VCO.
The output I found was accurate enough such that only the last
place in a 10-digit counter varied when it was locked to a
rubidium standard. Had it not been just bread-boarded at the
time, I expect it would have been an order better than that.
   
   If I were to try this all over again though, I'd use one of
the relatively cheap GPS modules with 1-pps outputs now available
and go the W5OJM way as noted above.
   
   
   Cheers - Joe
   

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