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

[Brian Lloyd]

On Jun 5, 2008, at 8:44 PM, Ron D'Eau Claire wrote:

> Aaargh! I meant to say we used high level I.F. limiters so no AM  
> would get
> to the detector. That included noise.

Right. If you use a discriminator there was amplitude sensitivity in  
the detector so limiters stages were used in the IF before the  
discriminator. A ratio detector compensated for signal amplitude and  
didn't require a dedicated limiter stage. PLL-based detectors were  
also immune to amplitude variations.

I worked my way through my last year in high-school working for an  
outfit that provided commercial two-way radio systems. (I did a  
*bunch* of installations in police cars.) We sold EF Johnson too. I  
hated those radios because the crystal ovens kept failing. Fixing them  
was not considered high on the list of fun jobs so guess who got to  
fix all the damned crystal ovens? :-)

We did Motorola too. The Motorola stuff was just better built. We  
always felt that Motorola was the best, GE next, and EF Johnson was  
what you got when you couldn't afford anything better. I know that  
when I was building repeaters I preferred Motorola or GE RF decks.

> 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...

Hey, you've been around linear radios for too long. It could happen to  
anyone. :-)

--

73 de Brian, WB6RQN
Brian Lloyd - brian HYPHEN wb6rqn AT lloyd DOT com