[ntp:questions] Re: WWVB 60kHz Receiver
David L. Mills
mills at udel.edu
Tue Apr 25 03:08:20 UTC 2006
Understand the situation here has deteriorated to the point that I can't
hear the signal at all with a good antenna and communications receiver.
The signal is thorougly covered in wideband hash from the power line. A
wee OEM board and loopstick simply won't cut it with any algorithm. The
only way to do that may be to synchronoualy demodulate the I and Q
components and use a state machine and maximum likelihood decoder
similar to the algorithm used in the WWV driver.
Jonathan Buzzard wrote:
> On Fri, 21 Apr 2006 21:11:07 +0000, David L. Mills wrote:
>>I've been down the fancy decoding path myself, e.g., the WWV driver,
>>which is a theoretically optimum linear receiver. However, much of the
>>crud found at WWVB and DCF77 frequencies is bursty, which is what my
>>LORAN-C receiver and program is good for. The Spectracom receiver is
>>actually quite good: however, it was designed to cope with Gaussian
>>noise, not suffer a 20-dB clobber by an interfering buzzsaw signal.
>>My precerred approach, should I accept the assignement, would be to tap
>>onto the I and Q baseband signals in the radio, chop at something like
>>10 kHz and feed to the L and R inputs on a sound card. I can take it
>>from there. My problemis that the SNR has become so degraded that the
>>very good PLL in the radio doesn't lock up.
> But that requires a much more expensive receiver than a little OEM board
> with short ferrite rod. So my algorithm is designed to work with what I
> have which is just level transitions and times there of.
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