[Elecraft] K3 APF Adjustable Q

Robert Harmon k6uj at pacbell.net
Mon Nov 1 00:52:14 EDT 2010 

It makes sense to me Joe, (sorry Guy)  

If you want a "milder shape" you don't really need APF.
Milder shape is the opposite of "peaking"

Bob
K6UJ



On Oct 31, 2010, at 4:33 PM, Guy Olinger K2AV wrote:

> You've brought that up several times, Joe, but that is not the sound,
> and how do you use it in CW with Shift increment at .01, particularly
> with DUAL PB turning APF on and off?  73, Guy.
> 
> On Sun, Oct 31, 2010 at 4:47 PM, Joe Subich, W4TV <lists at subich.com> wrote:
>> 
>>>> What I have been trying to point out is that there is a general
>>>> benefit for a milder shape, that one MAY leave on all the time,
>>>> and tweak to tight as needed.
>> 
>> If you want a "milder" shape, use Dual PB filter with a 400 - 500 Hz
>> background and 100 Hz foreground.  That can certainly be left on
>> all the time and the APF switched on when needed ... at least once
>> all of the controls have been programmed.
>> 
>> 73,
>> 
>>   ... Joe, W4TV
>> 
>> 
>> On 10/31/2010 12:03 PM, Guy Olinger K2AV wrote:
>>> 
>>> I'd say for variable Q, the tightest setting should be just what is
>>> there now.  So no one is losing anything.
>>> 
>>> What I have been trying to point out is that there is a general
>>> benefit for a milder shape, that one MAY leave on all the time, and
>>> tweak to tight as needed.  MP's EDSP, 450 Hz sidetone, NR=D, Contour=
>>> 11 oclock as an example of a mild contour that is really helpful.
>>> 
>>> Being able to tune the APF tight setting around allows me to match the
>>> "tone" of the almost ring to the remembered tone of the weak station
>>> and have it come up when I hit it.
>>> 
>>> If the choice is sharp or no APF and no APF tune, I have to RIT the
>>> station to sidetone.  This has a couple of disadvantages.
>>> 
>>> First, if running in a contest, and there are very loud stations up
>>> and down (aren't there always?), RIT up and down is going to let the
>>> co-channel guys in under the roofing filter and into pre-APF digital
>>> space. That can't be useful.  Second, continuing to tune the station
>>> in becomes hard if the station stops or fades out because there is
>>> nothing to "calibrate" the completion of RIT twiddle other than
>>> hearing the tone from the station move to sidetone, and now it's
>>> stopped or faded.
>>> 
>>> The presence of APF tune, or variable Q does not disadvantage anyone
>>> who doesn't need them, the same way all the really neat digital stuff
>>> does not disadvantage the straight CW operators.  The current setting
>>> and shape of APF is definitely the right max Q setting, and does very
>>> well for me.
>>> 
>>> I just want a mild Q setting to imitate the shape I had with the MP
>>> all those years.  Those who hear it will get it, just like those that
>>> hear the sharp APF for the first time and try it, get it.  I think a
>>> lot of people will leave a mild Q on ALL THE TIME for general
>>> operating.  It lowers the level of the stuff up and down a little
>>> without any ringing, but still allows one to hear up and down for off
>>> frequency callers.  For me it's an EASIER listen for hours on end.
>>> 
>>> 73, Guy.
>>> 
>>> On Sun, Oct 31, 2010 at 10:47 AM, Steve Ellington<n4lq at carolina.rr.com>
>>>  wrote:
>>>> 
>>>> 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"<lists at subich.com>
>>>> To:<elecraft at mailman.qth.net>
>>>> 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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