Posted by
Guy, K2AV on
Feb 02, 2010; 11:42pm
URL: http://elecraft.85.s1.nabble.com/Attenuator-and-RF-Gain-Settings-tp4503505p4504543.html
In the K3 there are *TWO* kinds of noise blanking. One is digital and
runs inside the firmware program. The other is the same hardware IF
blanking that has been in use in analog radios for over 50 years. They
do not work at all alike.
The hardware blanking has advantages on some noise and was retained as
one of the blanking options (marked IF). Hardware blanking, as it
always has, will create extra noise from strong signals, because it is
modulating the spectrum with a square transition of IF gain from on to
off. The artifacts are just a matter of physics in anyone's radio.
Hardware blanking is hardware blanking.
The digital "blanking" (dSP in the NB menu selection) uses algorithmic
methodology and does not produce these artifacts. It is a better
phrase to call the dsp version "noise cancellation".
Press and hold NB to bring up the NB level menu and turn IF OFF with
the VFO B knob. Luckily, at my QTH I have not found a point where I
need the hardware blanking. Whatever causes my 160m S9 (50uV in 50
ohms) daytime buzz (not found in two years of searching) is reduced to
S6 (6uV) by the dsp blanking, but only to s7/s8 (12 to 25 uV) by
hardware blanking. When the buzz is gone, ambient 160m noise at SSB
bandwidths is S6.
Also be sure to use as little of the ATT-nothing-PRE gain range as you
can, as this ramps up the pulses as well as the wanted signal.
Keeping this at a minimum allows me to use the dsp blanking.
73, Guy
PS, I have my S meter set to ABS (absolute) and have done RF gain
calibration, and so my S meter CAN be read in uV when AGC is on.
On Tue, Feb 2, 2010 at 3:40 PM, juergen <
[hidden email]> wrote:
> Hi Lance
>
> This issue is a real problem for me. If I turn the AGC off I need too use the noise blanker. This ruins the K3's strong signal handling performance. Normally I dont need to use the noise blanker. However with the AGC off, electric fence pulses are loud as hell because the pulse stretching blanker is not on with the AGC off.
>
> This problem with the K3's producing noise with AGC on is real problem.
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