https://www.febo.com/pipermail/time-nuts/2017-April/thread.html
Yesterday we swept our HP5061B thru the cesium resonance curve. As far as I know this is the first time that the curves have been published. The original phase modulation is a very unlinear sine wave frequency sweep. We built a 100 ms time constant integrator for the 20 cps triangle from the function generator. When a triangle is integrated, the result looks much like a sine wave but it is not. It is really back to back parabolas as shown in http://gonascent.com/papers/hp/hp5061/waveform/dblepara.jpg . The waveform is actually inverted in the display. Note that it appears a bit squashed. That small difference results in a linear triangle frequency sweep. We drove J1 on the A3 board with the output of the integrator and turned R20 the Mod Level pot all the way up. The phase modulation differentiates the output of the integrator to restore linear sweep. We ran the electron multiplier output J1 which went into the A7 board into scope channel two see http://gonascent.com/papers/hp/hp5061/waveform/csweep.jpg Vertical was 5 millivolts per division inverted. Ground is shown by the yellow 1 arrow and the scope amplifier was providing the 1 MΩ termination. The corresponding peak beam current is 20 nA or 20 on the HP meter. Because of the varactor polarity, the frequency sweep is inverted and is from -1,200 cps below resonance to +1,200 cps above resonance. The center of the negative going sweep of the triangle is the peak response of the cesium tube while being swept from low to high frequency. At -550 cps below it and +550 cps above it are seen the two valleys of the main resonance peak. The center of the positive going sweep of the triangle is also the peak response of the cesium tube while being sweep from high to low frequency. The valleys either side of the main peak are seen again along with partial false peaks. As you approach the positive peak of the triangle the lower false peak is seen. As you approach the negative peak of the triangle, the upper false peak is seen. Integrator limitations kept us from having enough drive levels to see the complete lower and upper false peaks. Remember that the sweep is reversed at both peaks of the triangle, low to high and high to low. See the artists depiction at Figure 4-43 in the manual. πθ°μΩω±√·Γλ WB0KVV _______________________________________________ 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.