Ryosuke, Yutaro, Kiwamu,
We discovered today that two out of ten RF outputs of the harmonic generator had appreciably low RF outputs. This issue may need to be addressed.
We figured this out when measuring the RF power at various points to determine the necessary RF attenuators as part of the demodulator checkout (klog 8231). We are wondering whether they have been low from the beginning.
Measurement summary
Here is a summary table of the RF power measured directly at the front panel of the harmonic generator (S1909724) at the IOO rack (D1706814-v9). The measurement values from the manufacturer can be seen in the same link.
| Multiplication factor (names) | measured RMS [mV] | RF power [dBm] | Measurement by the manufacturer [dBm] | Difference from factory measurement [dB] | Notes |
| x 2 | 880 | 11.90 | 13.5 | -1.6 | |
| x 3 (f1) | 850 | 11.60 | 12.9 | -1.3 | |
| x 5 | 782 | 10.87 | 12.9 | -2.03 | |
| x 6 (2f1) | 876 | 11.86 | 12.6 | -0.74 | |
| x 7 | 716 | 10.11 | 12.1 | -1.99 | |
| x 8 (f2) | 615 | 8.79 | 13.0 | -4.21 | sad |
| x 9 (3f1) | 892 | 12.02 | 13.4 | -1.38 | |
| x 10 | 756 | 10.58 | 13.2 | -2.62 | |
| x 16 (2f2) | 427 | 5.62 | 12.6 | -6.98 | sad |
| x 30 | 760 | 10.63 | 13.5 | -2.87 |
Measurement setup
We used an oscilloscope, DSO-X 3054A, configured for DC coupling with a 50 Ohm input imepdance. The oscilloscope has an measurement bandwidth of 500 MHz and therefore we think all the measurements were valid. The RF signal was coupled to the oscilloscope via a 2-m long SMA cable with a BNC-SMA adapter at one of its ends to hook it up to the oscilloscope input. We also cross-checked the signal level by comparing a same RF signal against that measured with a MockLab which didn't show appreciable discrepancies at around 90 MHz.
The seed source for the harmonic generator is an N5181B, outputing a 5.624308 MHz sinusoidal signal with an amplitude of 10 dBm.
In addition, we performed another calibraion check where we plugged the oscilloscope directly to the seed source instead to the harmonic generator. It seems that the oscilloscope has a good enough calibration. The below is a summary of the calibration check.
- 5 MHz, 10 dBm output: 720 mV rms (or 10.16 dBm)
- 45 MHz, 10 dBm output: 715 mV rms (or 10.10 dBm)
- 90 MHz, 10 dBm output: 713 mV rms (or 10.07 dBm)
- 150 MHz, 10 dBm output: 710 mV rms (or 10.04 dBm)
