[Elecraft] K3: Noise Reduction (NR) in FM Mode

[Matt Zilmer]

At least with the Motorola Syntor X, they used a separate and very
simple receiver to pick out impulse noise and used this secondary RX
detector output to poke holes in the main RX audio.  They called it an
Extender and I believe it was only included with the low-band Syntor
X.  It is described as a Noise Blanker.

I have one of these LB Syntor X's in mobile use, but have never found
a situation where the Extender was needed (or a way to real-world test
it!).  Turning the Extender on or off has no apparent effect on
receive sensitivity however.  I've watched the blanking pulse train
from the Extender outpt to the blanking circuit on the main RX - the
pulses are present, but can't really be heard in the main.

Shamless Plug:  my little company makes agile controllers for the Moto
Syntor and Syntor X radios.  This is the only reason I know this
fairly useless bit of trivia.

73,
matt, W6NIA

On Thu, 05 Jun 2008 20:44:27 -0700, you wrote:

>Aaargh! I meant to say we used high level I.F. limiters so no AM would get
>to the detector. That included noise.
>
>So "blankers" were never needed. 
>
>Maybe Motorola didn't use good limiters.
>
>Now to see if I can pry my foot out of my mouth... 
>
>Ron AC7AC
>
>-----Original Message-----
>??? 
>
>I worked on FM gear in the land mobile business as a service rep and
>salesman and we *never* used a noise blanker. A limiting I.F. amplifier was
>a basic part of the receiver design since the detector does not respond to
>amplitude modulation at all, including noise.
>
>Noise does not modulate the frequency. 
>
>Maybe Motorola didn't use good FM detectors. Some simple types of "FM
>detectors" respond to both AM and FM.
>
>Come to think of it maybe that's why I outsold Motorola in our market area
>with E.F. Johnson land mobile FM gear <G>. 
>
>Ron AC7AC
>
>
>-----Original Message-----
>
>Hi John
>When I worked for Motorola, both their and GE's top of the line two-way FM
>mobile radios did include noise blankers for the mobile environment.  They
>worked quite well for their intended use. 73, Bob N6WG
>
>_
>
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