Cabinet resonance

[Ken Kopp]

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
[hidden email]


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[Jozef Hand-Boniakowski]

The K1 with the speaker does the same thing albeit at a higher
frequency.  A couple of extra screws dead center on the top cover on
either side might cure that?  What do people think?  I use headphones
most of the time, but the lid resonance is not the best thing when
showing the rig off.

Jozef WB2MIC
Wells VT

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
> [hidden email]
>
>
> _______________________________________________
> Elecraft mailing list
> Post to: [hidden email]
> You must be a subscriber to post to the list.
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[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
> [hidden email]
>
>
> _______________________________________________
> Elecraft mailing list
> Post to: [hidden email]
> You must be a subscriber to post to the list.
> Subscriber Info (Addr. Change, sub, unsub etc.):
> http://mailman.qth.net/mailman/listinfo/elecraft
>
> Help: http://mailman.qth.net/subscribers.htm
> Elecraft web page: http://www.elecraft.com

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