The output of the AD8307 will be a voltage proportional to the power of the RF signal produced by the radio source and received by the radio telescope. Since radio sources emits a signal that could be as a white gaussian noise, the voltage from the AD8307 need to be integrated and then properly magnified, in order to be able to observe also the very small signal increasing, in the noise floor, produced be weaker radio sources. This is done by some operational amplifiers circuits:
Zero level tuning (R16) and centre scale tuning allows additional amplification of the signal, in order to set the proper range of operation within the full range of the analog to digital converter, obtaining the best resolution.
U1b introduce an integration constant, selectable by JP1, between 50ms and 5s, while U1c provide the final signal amplification.
A FULL CIRCUIT SCHEMATIC FOR PREVIOUS TWO BLOCKS CAN BE DOWNLOADED HERE:
AD8307 and DC circuits.pdf