Just when you thought it couldn’t get more boring (reference my last post about signal generator calibration…
I did all these careful calibrations of my signal generator to check its accuracy and linearity. Everything looked good, except that the signal reading was about 1 dB low.
HP power meters have a calibrator providing a 50 MHz signal at 0 dBm that is (supposedly) very precise. I have a total of four meters with those calibrators, and I decided to cross check them. Three of the four were within 0.01 dBm of each other. The fourth was 0.50 dBm high. Guess which one that was? Yup, the newest, fanciest one in the collection (HP 438A, so not *that* new) — that had been calibrated just about a year earlier.
I reran the tests using the 436A meter and bingo — the signal generator readings were now less than 0.1 dBm at 50 MHz, and at 10 MHz through the test cables and adapters, about -0.3 dB, which is perfectly reasonable.