Hi > On May 16, 2017, at 10:04 PM, Donald E. Pauly <[email protected]> wrote: > > https://www.febo.com/pipermail/time-nuts/2017-May/105298.html > > We recently got our second HP5061B to lock after changing the beam > tube. We did no alignment with the exception of changing the gain on > Beam current. Ion current dropped from 14 to 1 with only a few hours > of operation of the instrument. We obtained momentary lock but lost > it after a couple of minutes. The trouble was a blown themal fuse on > the HP10811 oscillator which shut down the oven. We have TEMPORARILY > jumpered it while the correct fuse is on order. > > We aligned the C Field on #1 but have not done that alignment on #2 yet. > The 5 mc output of our #1 instrument was compared to the 5mc output of > #2 with an HP10514A balanced mixer. Two input ports L and R are > multiplied by internal Shottky diodes to produce an X output which can > be terminated in 50 Ω. Maximum input current on both the L and R port > is 40 mA or 2 V rms. One instrument was put in Open Loop and the > fine frequency adjusted to approach quadrature. It was then returned > to OPR and steered to final quadrature with the C Field. > > We used a digital voltmeter with a resolution of 10 uV dc to measure > the X output of the mixer with the L and R inputs in near quadrature. > The mixer output contains a large 10 mc component of about 2 V peak of > peak which rides on the dc representing the phase difference. The dc > output for in phase and out of phase inputs is about +1 and -1 Volts. > Our calculated sensitivity was 31 uV per picosecond of error when > within a few degrees of quadrature. Lock within a few picoseconds was > obtained by adjusting C field on #2. It had to be continuously > manually steered. We could not look at the X output on the scope > because of the large rf level present. Our digital meter might have > been experiencing rf overload causing inaccuracy at low dc voltages.
Keep in mind that the mixer has millivolt level offsets and millivolt level drift (over a wide range). > > Continuous lock was lost a few times on #2 which we attributed to it > needing a complete alignment. Second harmonic was only 22. There is a gain pot that “sets” the second harmonic. It can be low and the device will still lock. Bob > The > procedure in 5-217 g for modulation adjustment is not very scientific. > It calls for adjusting modulation for maximum 137 cps out of the AC > amplifier board when the beam tube is driven at 5x10^-9 below the > resonance line. Modulation is then to be reduced by 5%. This affects > all other adjustments. > > We decided to directly measure this deviation with precision. The > phase noise of the 90 mc output of the A3 multiplier board was > measured as well as the modulation. The spectral width of our > function generators at 5 mc was compared to the HP5061B 5 mc output. > Our adventures with this project will be covered in a separate post. > > πθ°μΩω±√·Γλ > WB0KVV > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
