John Ackermann N8UR wrote: > I had a chance to measure a TADD-1 using an HP-3048 phase noise system > last year. I've attached a screen shot of the results; in short it was > below -140dBc/Hz from 100 Hz on out (by the way, I'm not sure I would > trust the noise floor shown in this test; I am not certain we had the > best test set-up). That's within a few dB of what HP said their 5087A > amplifier would do. > > I'll soon have access to a new phase noise measurement system and will > relook at the TADD-1 performance with it. > > John > > John
My calculations using the component values in the circuit indicate that the TADD-1 noise figure should be about 19dB and its corresponding phase noise floor should be lower than -160dBc/Hz. when the input signal is +7dBm or greater. So unless you had an unusually noisy set of opamps and/or resistors the measurement setup phase noise floor probably exceeds that of the TADD-1 by around 20dB. With a 10V supply instead of 9V and a +13dBm input the phase noise floor should be about -168dBc/Hz which is respectable but a few (~10) dB shy of the state of the art. The only way to achieve the state of the art performance with opamps using a 9 or 10V supply is to use lower noise (2nV/rtHz appears feasible) opamps pairs driven in push pull by an input step up (1:2 turns ratio) transformer with an output stepdown transformer driven in pushpull by the 2 opamp outputs. The noisy 1K input protection resistor would also have to be reduced in value as would the opamp feedback network resistors. NIST's 1995 distribution amplifier claims a phase tempco of 0.3ps/K and 120dB isolation between channels. http://www.physics.nist.gov/News/Update/950626.html Bruce _______________________________________________ time-nuts mailing list [email protected] https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
