Re: K3: RF Gain, Squelch

Posted by Don Wilhelm-4 on Jan 12, 2010; 5:10am
URL: http://elecraft.85.s1.nabble.com/K3-RF-Gain-Squelch-tp4289745p4289879.html

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:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html