[Elecraft] Subject: "Another Better Mouse-trap?"

[Wes Stewart]

The problem with a second receiver tuned (significantly, like Collins) out of band is that the noise isn't always the same at the two frequencies.

IMHO, the problem with most blankers, as mentioned below, is that the designers don't introduce any delay in the signal path.  It takes some time to amplify, detect and form the blanking pulses that drive the noise gate.

Absent delay, the noise pulses get through the gate and do their mischief before the blanking takes place.

See: http://k6mhe.com/n7ws/Noise_Blanker.pdf

Wes  N7WS

--- On Fri, 8/7/09, JIM DAVIS <nn6ee at astound.net> wrote:

> From: JIM DAVIS <nn6ee at astound.net>
> Subject: [Elecraft] Subject: "Another Better Mouse-trap?"
> To: elecraft at mailman.qth.net
> Date: Friday, August 7, 2009, 2:42 PM
> 
> This idea was put forth by "Don-W6JL" (Fallbrook, CA)!!!
> 
> His quote: "  I have tested many "noise blankers" in
> modern rigs, on the air.  Both the I.F. noise 
> gates and the DSP-based “noise reducers”.  Not one
> works the way I feel it should.  I think you 
> need a separate noise receiver, independent of the main
> receiver, and tuned to a frequency that is 
> outside of a ham band.  (There have been excellent
> homebrew receivers using this approach for 
> noise blanking).  This then drives the noise gate, and
> is timed so that it gates the I.F before 
> the noise pulse arrives there.  A good blanker should
> have 40 dB minimum of noise pulse 
> suppression, with adjustable blanking level and
> widths.  I notice the K3 has these features, but 
> it still does not seem to reduce impulse noise more than an
> S unit or two (6-12 dB), which is 
> inadequate.  I do not use blankers here myself; my
> entire station is homebrew and the receiver is 
> a phasing, image cancelling job with no blanking at all,
> (or AGC for that matter).  I get along 
> fine with neither, even in contests."
>