First off, you need to have a good calibrated signal generator… calibrated in db (or mv so that you can convert to db) that is either variable output or you have a good/accurate variable attenuator.? I have both and I test them against each other because there is a very slight variation of about 0.5 db between them.

?

I have an old Agilent N5182 and it will output a signal down to -110 db (and I can use a variable attenuator that).? ! connect the signal generator via the attenuator to the radio RF input.? Turn the radio on, set the radio and signal generator to a frequency (lets say 10.0000000 MHZ for kicks)… the signal generator acts like a dummy load (has adjustable impedance to match output power setting).? I start at about -150 db on CW, turn the radio volume way up in SSB (important… specified filter), and then start lowering the attenuation until I FIRST notice a signal.? Now you can also so this with an RMS volt meter on the speaker leads but I find I don’t need to do that.? Find the point where I initially hear the signal generator and subtract 1 db.? that is the sensitivity; and the input in mv for (S+N)/N that gives 10 db.

?

It's a bit black magic but as long as you are consistent (and have a reference that someone else did to calibrate your readings to) its OK.? I have several radios on Sherwoods list to use as references.

?

?

Dr. William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ VP2EHZ

?

Owner - Operator

Big Signal Ranch – K9ZC

Staunton, Illinois

?

Owner – Operator

Villa Grand Piton – J68HZ

Soufriere, St. Lucia W.I.

Rent it:

?

Moderator: North American QRO Group at Groups.IO.

Moderator: Amateur Radio Builders Group at Groups.IO.

?

email:? bill@...

?

?