[Elecraft] KFL3A-6K-IR Filter

[Joe Subich, W4TV]

> Band width was 6k Hz, offset 0. When I turn the band width knob I
> only get a spread of 5k. Any suggestion would help.

This is normal.  The "BW" display shows the audio bandwidth not the
IF bandwidth.  Audio bandwidth is defined as FC + WIDTH/2

In the case of [double sideband] AM, the IF bandwidth is twice that
of the audio bandwidth.  Thus a "6 KHz" filter provides roughly 3 KHz
of audio bandwidth at -6dB (the filter is nominally 6.125 KHz wide
between the -6 dB points - about 7.5 KHz at -30 dB and 9.35 KHz at
-60 dB) and rolls off rather quickly above 4.2 KHz due to the audio
lowpass filter that follows the digital to analog converter.

If you change Shift/Width to High/Low you will notice the maximum
setting for "HIGH" is 4.2 KHz - a design limit in the DSP due to the
clock frequency of the digital to analog converter.

73,

   ... Joe, W4TV


On 8/8/2016 3:35 PM, Grady Harper via Elecraft wrote:
> I have just installed a new 6K AM filter in my K3s.  I configured the
> filter by computer, and checked using CONFIG .  Band width was 6k Hz,
> offset 0.  When I turn the band width knob I only get a spread of 5k.
> Any suggestion would help.
>
> The filter was put in slot 1.
>
> Sent from my iPad
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