I measured the output DC voltage of the satellite amplifier box at PDMon port when the PDA input was shorted and got following offsets:
| CH |
Output Offset (mV) |
CH |
Output Offset (mV) |
| 1 |
6 |
5 |
750 |
| 2 |
140 |
6 |
120 |
| 3 |
350 |
7 |
537 |
| 4 |
40 |
8 |
670 |
However, I think I'm making a mistake while measuring this offset as well as all the noise measurements of this satellite amplifier box so far. Since it is a current input, transimpedance circuit, the noise of the circuit should be measured with open input, not closed. Infact, by shorting the PDA input, I'm giving DC path to input bias current of AD833 transimpedance amplifier to create this huge DC offset. This won't be the case when a photodiode is connected at the input which is a capacitor and hence no DC path is allowed. So my issue of offset was bogus and past two noise measurements in 40m/15797 and 40m/15793 are wrong. |