[time-nuts] WWVB teensy BPSK early experiments

[Mike Feher]

Too bad I am an old retired hardware engineer and know nothing about these new SW controlled devices. Have Fun - Regards - Mike 

Mike B. Feher, N4FS
89 Arnold Blvd.
Howell NJ 07731
848-245-9115

-----Original Message-----
From: time-nuts <time-nuts-bounces at lists.febo.com> On Behalf Of paul swed
Sent: Sunday, November 1, 2020 12:48 PM
To: Discussion of precise time and frequency measurement <time-nuts at lists.febo.com>
Subject: Re: [time-nuts] WWVB teensy BPSK early experiments

John sent the link on the teensy wwvb AM receiver. It can easily be shifted to other frequencies. Using the work Frank dcf77 and then Chris wwvb did with the PJRC audio design tool gives quite a bit of insight to the work that was done.
The system assumes a sample rate of 192Khz. That limits the receive range to about 98KHz.
I have not been able to confirm the rate I am using is 192Khz and when the set command is used its not recognized. So somethings up.
The design Chris has essentially is a microphone input with some 38 db of gain feeding a bandpass filter around 60 KHz to a multiplier (RF mixer) then a low pass filter. Chris and Franks design is much more than these few words with spectrum display, signal level, and AGC.
So without any effort the frontend solution is sitting in the teensy that cuts out a bunch of typical wiring. Granted its not as tight as discrete components can be. But its a chunk of software code. No digi key orders for L & Cs... :-) The output of the chain is 600 Hz audio that does contain the phase changes.

But the trick is creating the true I & Q channels. Not an issue to add a second multiplier and chain did that last night. But at someplace a 90 degree phase change or delay needs to occur.
Or as suggested a hilbert transform.
Regards
Paul
WB8TSL