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. Continuous lock was lost a few times on #2 which we attributed to it needing a complete alignment. Second harmonic was only 22. 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

Hi > On May 16, 2017, at 10:04 PM, Donald E. Pauly <trojancowboy@gmail.com> 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 -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there.