[Elecraft] Cabinet resonance

[Stewart Baker]

I 'de-tuned' the top cover of my K2 by gluing a thick piece of felt to the 
inside surface. It stops a lot of rattles as well.

73
Stewart G3RXQ

On Fri, 30 Mar 2007 17:31:47 -0000, Ken Kopp wrote:
> The combination of the cabinet and speaker of my
>
> K2 (#5665) has a VERY pronounced resonance at
> about 450 Hz.  How fortunate, as this is the frequency
> at which I like to copy CW. (:-)
>
> The resonance is so pronounced that it would present
> a problem if I wanted to use a higher frequency, say
> 600 Hz.  It initially caused me a bit of consternation as
> I was setting up the filters ... until I realized what was
> going on.  Even with the filter set up for 600 Hz I would
> still find myself tuned and listening lower than the "Spot"
> tone ... sort of a human AFC circuit. (:-)
>
> Has anyone else noted this?  I wonder if all the speakers
> supplied with K2's are of the same design from the same
> supplier?
>
> Mine -does- have all options installed except the battery
> and I assume the resonant frequency of the box would be
> different ... or non-existant ... with different "fillers" inside
> the case.
>
> I have two of the "old" Skytech variable-resonance speakers
> stored away that are fine examples of the application of
> housing / speaker resonance as a CW aid.  They use a sliding
> tube to "tune" the  assembly.
>
> 73!  Ken Kopp - K0PP
> k0pp at arrl.net
>
>
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