I bought a HP8970B (serial prefix 2950A), and I am not sure of the state of the internal RAM backup battery. The service manual says to check address 65460, which should contain 128, if the stored IF gain/attenuator calibration values are OK. I found "27" there, which would indicate lost calibration. But the 8970 signals no error on power up or measurement.? Also, the values at 6992 (from sf 93.3) and on, seem quite reasonable as 5dB steps (3.173, 10.189, 32.339, 100.44, ....).
So I am not sure if the instrument is accurate. Other operator checks (own NF etc) come out OK, it also produces reasonable NF and gain results.
I will replace the battery in any case, but should I try to keep the existing values, either by providing backup power, or manually re-typing the extracted values?
Or, should I do a full calibration? I think I have all the gear needed. I guess HP437 instead of 436, and HP3457 instead of 3456, would be OK? (also have 435 and 3455, if these would be better suited.)
