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KFL3A-6K-IR Filter

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KFL3A-6K-IR Filter

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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Joe Subich, W4TV-4

Re: KFL3A-6K-IR Filter

> 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
> ______________________________________________________________
> Elecraft mailing list Home:
> http://mailman.qth.net/mailman/listinfo/elecraft Help:
> http://mailman.qth.net/mmfaq.htm Post:
> mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net Please help support this
> email list: http://www.qsl.net/donate.html Message delivered to
> [hidden email]
>

Leroy

Re: KFL3A-6K-IR Filter

Thanks Joe for clearing that up. I had read and read and still
could not sort that one out.

Thanks Leroy AB7CE

-----Original Message-----
From: Joe Subich, W4TV
Sent: Wednesday, August 10, 2016 8:16 AM
To: [hidden email]
Subject: Re: [Elecraft] KFL3A-6K-IR Filter

> 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:

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