Don and Al... Thanks for the explanations. Yes, this does indeed make sense. Finally that mystery is behind me.
phil On Jan 11, 2010, at 9:10 PM, Don Wilhelm wrote: > Al, > > To look at it another way - look at the S-meter to observe the band noise > level, and then back off the RF gain until the S-meter is steady at that same > S-meter reading. Of course, this should be done at a spot in the band where > no signals are present. > > That is a quick way to determine the optimum setting for the RF Gain > consistent with the greatest receiver dynamic range and one does not have to > listen to the constant band noise clutter. > > The other option is to just run with "all knobs full right" and put up with > listening to the band noise when there are gaps in the signal level. > > Be aware that the AGC Threshold will also have a great effect on the amount > of band noise heard in the audio. If the Threshold is set too low, the > receiver will go into AGC action on only the band noise. I use an AGC > Threshold setting of 008 just for that reason (I know the default is 005, but > I think that is too low). > > 73, > Don W3FPR > > Alan Bloom wrote: >> On most radios, the term "RF Gain" is actually a misnomer. The control >> should really be called "IF Gain". >> >> The way most HF receivers work is that turning down the "RF Gain" >> control simply applies a DC voltage to the receiver's AGC circuitry. >> For example, if an S9 signal causes the AGC voltage to rise to 1.23 >> volts, then when you set the RF Gain control to place 1.23V on the AGC >> line, the S meter will read S9 even when no signal is present. In that >> case, signals below S9 do not change the gain or S meter reading. >> Signals above S9 cause the AGC/S meter to rise as before. >> >> Turning down the RF gain control causes the receiver to sound less noisy >> because the IF gain is limited to some maximum value. If you set it >> right you can still hear the weak signals (taking advantage of the human >> ear's dynamic range) but you don't have to put up with so much noise. >> >> On the noisy low bands I generally set the RF Gain control so that the S >> meter reads nearly constant when no signals are present, bouncing up >> slightly only on the biggest noise peaks. >> >> Al N1AL >> >> ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
