> On 3/14/12 8:07 PM, J. Forster wrote: >>> John >>> Like your thought. I seem to remember costas loops work like that to >>> recover the carrier. >> >> Paul, >> >> It recovers a bipolar signal to steer the local VCO as well as the >> data.. >> It also needs a quadratue hybrid at the VCO frequency (although it might >> be fairly easy to make a quadrature oscillator vat 60 kHz.) > > One easy scheme is to make your VCO run at a multiple and divide down to > generate the two quadrature square waves.
Doesn't look like that works with the HP 117A. I don't know about other receivers. >>> Had seen it in amsat many years ago. So perhaps an approach is to limit >>> if possible the incoming signal. >> >> I'm not sure if it works properly with clipped (digital) dignals, off >> hand. > > Yes it will. Not w/o a quadrature drive to the mixer/multiplier. A square wave, multiplied by itself, has the same output as input. >>> Though further simple dumb thought. A NE602 or SA602 or also teh 612 >>> series. All the same mixer circuit (Or multiplier)will double the >>> incoming >>> frequency if you delay the incoming by 90 degrees I think. >> >> Sine and Cosine are orthogonal. You need to do (Sine)*(Sine) >> >> sin^2 (wt) = 1/2(1 - cos (2wt) >> > > This is like the classic squaring technique to receive PN coded signals > without knowing the code. (it's used in some "codeless" GPS receivers.. > you can retrieve frequency and phase) A Costas Loop recovers the bit stream and the carrier frequency (from the local VCO) from a BPSK. It is self syncronizing. I'm beginning to think that, for the HP 117A at least, a fix could be built on a small daughter board. Also, I think that NIST should do the engineering and maybe run the boards too. -John =============== _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.