If memory serves me correct that unit of measure was chosen by the Institute for High Fidelity (IHF) roughly 40 years ago as the unit to rate FM tuner sensitivity. The dBf unit was to replace the more common (at the time) microvolt since the dBf was a true power measument in positive whole numbers, while the microvolt rating was typically not "whole" and had an implied impedance that was not always stated, or met in practice. For example the Outlaw RR2150 is specified to have a "Usable Sensitivity IHF: 12dBf" (see: http://www.outlawaudio.com/products/rr2150.html). Other than for better FM tuners I've not ever seen the dBf unit used.
Bob LaJeunesse ________________________________ From: "Brian, WA1ZMS" <wa1...@att.net> To: Time-Nuts <time-nuts@febo.com> Sent: Wed, December 14, 2011 10:10:13 PM Subject: [time-nuts] Question..... OK......here's a question I never found a solid answer to: On the HP-8656A signal generators, one of the amplitude scale buttons is in dBf. dB relative to a femptowatt. (ie: -120dBm) What drove that requirement? I have yet to see a later vintage sig gen use that scale. -Brian, WA1ZMS _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.