[Elecraft] KX3 Receive Performance Below 1500 kHz

[Wayne Burdick]

Stephen,

The broadcast-band preselector components on the ATU option do in fact  
optimize receive performance in the 0.5-1.5 MHz range. However, the  
criteria being optimized by the preselector is rejection of harmonic  
images (typical of a zero-I.F. receiver), not necessarily sensitivity.

As I posted to the reflector in March of this year (and on other  
occasions), the KX3 includes a multi-pole high-pass characteristic  
within the T/R switch to attenuate mega-size BC band stations below  
1.5 MHz that might affect RF switches and PIN diodes. This is also  
noted in the Specifications section of the manual, under "Sensitivity  
(MDS)".

I see that the KX3 sales brochure isn't clear on this point, and I'll  
fix that.

One thing I can do in firmware is allow the user to manually tune the  
ATU's LC network to peak a given AM-band signal. I'll eventually add  
this as an alternative to the "canned" preselector settings, which  
were based on a compromise antenna (50' center-fed random wire).

73,
Wayne
N6KR


Stephen Prior wrote:

> Hi Wayne
>
>
> Have things changed then, since you wrote the following back last  
> October?
>
>
>
> "- switchable low-pass filter components that optimize receive
>  performance when you're listening in the AM broadcast band"
>
>
> I'm just wondering, because I too enjoy a bit of medium wave late at  
> night when camping.  It's no big deal of course!
>
> 73 Stephen G4SJP