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AF-1 audio filter

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L. D. Ingram

AF-1 audio filter

Hi,

With all the chatter about the AF-1 audio filter lately I thought i
would post how I mounted the AF1 and an audio amplifier in a small
case to use with my K2. If anyone is interested you can find the
pictures and comments on my web site at lawrenceingram.com. Click on
the Ham Radio tab and then select the AF-1 article.

73,

Larry Ingram AG4NN

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AC7AC

Re: AF-1 audio filter

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Hisashi T Fujinaka

Re: AF-1 audio filter

I wasn't paying enough attention lately. Does anyone have a comparison
of the audio filter in the AF-1 vs the one in the KAF2? I've wanted a
low pass filter for a while, and after seeing a youtube video of the
AF-1 I think that's what I'm looking for.

On Wed, 1 Dec 2010, Ron D'Eau Claire wrote:

> Very nice execution Larry!
>
> I don't use an outboard audio amp with my AF1. The built-in LM386 amp in the
> AF1 drives a pair of outboard speakers for me with good volume. Do you have
> an unusually noisy environment?
>
> 73,
>
> Ron AC7AC
>
>
> -----Original Message-----
>
> Hi,
>
> With all the chatter about the AF-1 audio filter lately I thought i
> would post how I mounted the AF1 and an audio amplifier in a small
> case to use with my K2. If anyone is interested you can find the
> pictures and comments on my web site at lawrenceingram.com. Click on
> the Ham Radio tab and then select the AF-1 article.
>
> 73,
>
> Larry Ingram AG4NN

--
Hisashi T Fujinaka - [hidden email]
BSEE(6/86) + BSChem(3/95) + BAEnglish(8/95) + MSCS(8/03) + $2.50 = latte
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AC7AC

Re: AF-1 audio filter

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L. D. Ingram

Re: AF-1 audio filter

In reply to this post by AC7AC

Ron,

Thanks for the complement; I enjoy seeing what I can do to make
something fit my needs.

I don't have a particularly noisy site but I have the radio sitting
on a shelf with another shelf just above it which makes the top
firing speaker in the K2 more difficult to hear. So I added the
amplifier to connect to a front facing speaker. I probably don't need
the extra audio level, but added it because I don't know what I might
connect it to in the future.

73,

Larry AG4NN

At 12:29 PM 12/1/2010, you wrote:

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L. D. Ingram

Re: AF-1 audio filter

In reply to this post by Hisashi T Fujinaka

Hisaahi,

I have used both and find both useful. The thing I like about the
AF-1 is the ability to shift the peak frequency.

73,

Larry Ingram AG4NN

At 12:34 PM 12/1/2010, you wrote:

>I wasn't paying enough attention lately. Does anyone have a comparison
>of the audio filter in the AF-1 vs the one in the KAF2? I've wanted a
>low pass filter for a while, and after seeing a youtube video of the
>AF-1 I think that's what I'm looking for.
>
>On Wed, 1 Dec 2010, Ron D'Eau Claire wrote:
>
>>Very nice execution Larry!
>>
>>I don't use an outboard audio amp with my AF1. The built-in LM386 amp in the
>>AF1 drives a pair of outboard speakers for me with good volume. Do you have
>>an unusually noisy environment?
>>
>>73,
>>
>>Ron AC7AC
>>

Hisashi T Fujinaka

Re: AF-1 audio filter

In reply to this post by AC7AC

I was looking for the KAF2 manual online to compare, but I didn't try
very hard. I'll have to try again tonight.

On Wed, 1 Dec 2010, Ron D'Eau Claire wrote:

> I don't have a KAF2 Hisashi-san. Of course, they are both active filters
> but, from the comments I've noted here on the reflector, it sounds as if the
> AF1 is more "aggressive" than the KAF2.
>
> The AF1 is predominately a narrow bandpass filter but it also has a low-pass
> filter section to roll off the higher frequencies. You can see typical plots
> of the bandpass characteristic in the AF1 manual available on the Elecraft
> web site (look under Manuals and Downloads/Mini-Modules/AF1 Audio Filter).
>
> I can say the AF1 behaves very much like most active filters I've used with
> about all the selectivity possible (in BPF2 position) without serious
> "ringing". The AF1 is also tunable from the front panel to match your audio
> frequency preference. Also, the high-frequency cutoff point of the low-pass
> filter is adjustable from the front panel and it has a front-panel audio
> gain control.
>
> Ron AC7AC
>
> -----Original Message-----
>
> I wasn't paying enough attention lately. Does anyone have a comparison
> of the audio filter in the AF-1 vs the one in the KAF2? I've wanted a
> low pass filter for a while, and after seeing a youtube video of the
> AF-1 I think that's what I'm looking for.
>
>