Robert wrote:
HP 3552A Transmission Test Set. Designed for testing telephone lines, its basically an AF signal generator, level meter, frequency meter, monitor amplifier and line iterface in a portable box. Ignoring the generator, the line interface will allow direct connection to supplies of up to 75V and the level meter measures noise down to -90dBm (600ohm) with low pass filters available. * * * Its specified for 40Hz to 60kHz but responds down to 10Hz. * * * A quick check of a switching supply gave -42dBm at 450Hz off load and -45dBm at 1.5KHz at 28mA. A nice general purpose audio tester that is not well known. Cost was less than $40.
Brings back fond memories of the HP and other TTSs. For power supplies used to run precision oscillators, though, one probably would like something that performs well below 10 Hz and with noise levels in the tens of nV range rather than the 3552's noise floor of tens of uV. A nice, quiet preamp will solve the latter problem, but you'd have to tear into the 3552 to conquer its LF limit.
When one gets serious about quiet regulators for oscillators, one has to think about what's inside the can. Often, there is an internal regulator with 10-1000 times the noise of your carefully-designed regulator (and, in the case of a GPSDO, digital circuitry trying to put noise on the oscillator supply, as well).
Best regards, Charles _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
