On 03/25/2016 05:55 PM, Bruce Griffiths wrote:
As long as BNC connectors are avoided as their phase shift isnt that stable.. A small mechanical disturbance will change it significantly. Actually low noise PN measurement systems can be very sensitive to cable movement. Bolting modules to a metal baseplate helps a lot as does using intermodule connections comprising SMA(m)-SMA(m) barrels rather than cables. There's also the question of mixer port termination.The nist paper by Walls and Stein indicates that capacitive termination of the IF port may be effective in reducing noise whilst maintaining a flat response fro dc to around 50KHz.Small value resistors in series with the RF and LO ports are then useful in reducing the VSWR.
I replaced the faulty attenuator in one of my HP 8648 signal generators. The "plumbing" in them is fascinating and instructive, rigid metal tubes with smooth, continuous bends rather than flexible coaxial cable, and mating with SMA connectors on both ends. My 8468C is good from 9 kHz to 3200 MHz, and where my 8568B only went to 1.5 GHz, I was able to test the 8468C with the least spec. Signal Hound, SA44B, that goes to 4.4 GHz. Ian, G4ICV, AB2GR -- _______________________________________________ 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.
