Posted by
Joe Subich, W4TV-4 on
Nov 01, 2010; 1:55pm
URL: http://elecraft.85.s1.nabble.com/K3-APF-Adjustable-Q-tp5688670p5693783.html
>> For some reason you keep thinking that Elecraft's APF is being
>> designed and programmed by Yaesu engineers....
No, I'm saying that there are significant reasons *not* to do
variable Q:
1) there is no available control. The "Width" control everyone
seems to want to use is already used in both the shift/width
and LO-CUT-HI modes. I for one, don't want to give up the
use of the Width control when APF is active.
2) reducing the Q will make APF much less effective as shown by
history with the FT-1000D. The later version of the FT-1000D
was ineffective compared to the original circuit in the 1000D
and FT-990.
3) The broader peaking (selectivity) of the MP/MK V contour circuit
so often cited as a prototype for "adjustable Q" is already
available using the existing Dual PB filter.
>> I'm in favor of having a variable Q on this APF system. It will
>> help improve copy with a tight algorithm that Lyle has written
>> for this one, while at the same time allowing me to open the Q
>> so that I can copy not as weak signals with gain, and less
>> ringing.
Ringing is a result of the selectivity and the fact that the APF
is implemented as an Infinite Impulse Response (IIR) filter. In
order to reduce the ringing you *MUST* reduce the selectivity and
that loss of selectivity will destroy the benefit of the APF.
There is very little difference in absolute selectivity between 30 Hz
in the alpha APF and the 50 Hz minimum selectivity in the standard
DSP filters. Since even the 50 Hz DSP filter has a modest but
detectable ring, adding the ability to "de-Q" the APF would provide
no benefit that can't already be achieved using either the 50 Hz
DSP or Dual PB filters.
>> I believe that Lyle will not destroy his own code by adding a
>> feature that Enhances the operation of what he's already created
>> for us.
The whole point is that adding the ability to de-Q the APF will not
enhance its operation. It can only decrease its effectiveness and
reduce APF performance to something already available using existing
capabilities.
In other words, if you want a filter with less ringing use the 50 Hz
or 100 Hz IIR DSP. If you want broad peaking with a wider background
use Dual PB. Use the correct tool for the job: don't try to use graft
a scalpel blade to an axe handle.
73,
... Joe, W4TV
On 11/1/2010 4:24 AM, The Smiths wrote:
>
> Joe,
>
> For some reason you keep thinking that Elecraft's APF is being
designed and programmed by Yaesu engineers.... Why is it that just
because Yaesu made a mistake with their rig that it means Elecraft has
to destroy THEIR APF just because they choose to add an adjustable Q
control? You have to have confidence that the APF can remain exactly the
same as Lyle and the gang has written it while still adding the ability
to open it up some? Just because Yaesu programmers weren't talented
enough not to destroy what they had built doesn't mean that Elecraft
will make the same mistake.
> Furthermore there are Alpha testers like myself that will make sure
that once the variable Q has been put in that when set to the Minimum
(narrowest) setting that it will still act and feel like it does now. Of
course you too could do the same as an Alfa software tester. This isn't
Yaesu where no one listens to the users once they choose to make a
change or adjustment to the code... Your say WILL matter if things sound
different once the feature has been improved for others. I really don't
think that you're giving Elecraft, it's programmers, or the Alpha
testers such as myself enough credit.
>
> I'm in favor of having a variable Q on this APF system. It will help
improve copy with a tight algorithm that Lyle has written for this one,
while at the same time allowing me to open the Q so that I can copy not
as weak signals with gain, and less ringing. I believe that Lyle will
not destroy his own code by adding a feature that Enhances the operation
of what he's already created for us. If he does, I will be the first to
let him know so he can re-program it.
> The Dual pass band filter is nice, yes, but if you've used your DPB
filter in the K3 you know as well as I do that it acts NOTHING like the
APF with a wider Q in suppressing noise and improving gain as we're
seeing on this current APF. Again, this is NOT a Yaesu rig...
>
>
>
>> Date: Sun, 31 Oct 2010 10:27:33 -0400
>> From:
[hidden email]
>> To:
[hidden email]
>> 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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