Re: K3 APF Adjustable Q

Posted by Steve Ellington on Oct 31, 2010; 2:47pm
URL: http://elecraft.85.s1.nabble.com/K3-APF-Adjustable-Q-tp5688670p5691498.html

If the caller is off frequency I would just use RIT to center him in my
passband as usual and let APF do it's thing.
Having used outboard APFs for years, the ability to adjust it's selectivity
is very important. If the band is quiet and the signal is very weak, I would
adjust the APF nearly to the point of oscillation then back it off a tad. If
the signal is weak but there is a lot of QRN, I would back off the
selectivity a bit further but still take advantage of some extra peaking
capability.

N4LQ
Steve

----- Original Message -----
From: "Joe Subich, W4TV" <[hidden email]>
To: <[hidden email]>
Sent: Sunday, October 31, 2010 10:27 AM
Subject: Re: [Elecraft] K3 APF Adjustable Q

>
>>> however the fixed Q has a bit of ring and at times I would like to
> >> back it off (widen) it just a tad.
>
> This is the same mistake Yaesu made in the FT-1000D; de-Qing the
> original APF made it useless in later radios.  This is the very
> reason not to add adjustable Q or reduce the Q of the APF currently
> in field test.  If you want a less aggressive filter that is centered
> on the sidetone, use Dual PB ... that's exactly what it is designed
> to do (and it does a very good job when used as designed).
>
> Adjustable center frequency is very important ... particularly when
> PB CTRL is set for Shift=.05 (to allow LO-CUT-HI to function) as
> the 50 Hz increments too course to tune APF using the VFO.  The user
> also needs the ability to adjust the peak independently in order to
> peak up an off frequency caller and not "chase them up the band."
>
> 73,
>
>    ... Joe, W4TV
>
>
> On 10/31/2010 8:58 AM, Steve Ellington wrote:
>> If I had a choice between variable center frequency and adjustable Q, I
>> would choose adjustable Q.
>>
>> My logic is: The center frequency automatically follows the sidetone
>> frequency so I have no need to adjust it however the fixed Q has a bit of
>> ring and at times I would like to back it off (widen) it just a tad.
>>
>> Otherwise it's a HUGE improvement, sounds great and I wish to thank those
>> who made it possible.
>>
>> 73
>> N4LQ
>> Steve
>>
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