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K3 APF Adjustable Q

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Guy, K2AV

Re: K3 APF Adjustable Q

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 <[hidden email]> 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<[hidden email]>
>> 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"<[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
>>>>>
>>>>> ______________________________________________________________
>>>>> 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
>>>>>
>>>> ______________________________________________________________
>>>> 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
>>>
>>> ______________________________________________________________
>>> 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
>>>
>>
>

P.B. Christensen

Re: K3 APF Adjustable Q

I suspect the moment variable Q were to become available, soon thereafter,
the next request would be for variable peaking amplitude. At some point,
Elecraft must decide what they want from APF -- is it an emulation of a
filter used in a transceiver from twenty years ago? Or, is it something
more? If it's more, then it may as well be a full-blown parametric EQ
channel with variable amplitude, variable frequency, and variable Q.

I tend to agree with Al's comment where he noted that sometimes the most
effective controls are the one's that are easily accessible to the op
without the need for added manipulation.

Paul, W9AC

----- Original Message -----
From: "Guy Olinger K2AV" <[hidden email]>
To: "Joe Subich, W4TV" <[hidden email]>
Cc: <[hidden email]>
Sent: Sunday, October 31, 2010 7:33 PM
Subject: Re: [Elecraft] K3 APF Adjustable Q

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 <[hidden email]> 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<[hidden email]>
>> 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"<[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
>>>>>
>>>>> ______________________________________________________________
>>>>> 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
>>>>>
>>>> ______________________________________________________________
>>>> 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
>>>
>>> ______________________________________________________________
>>> 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
>>>
>>
>

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Gary Ferdinand

Re: K3 APF Adjustable Q

As one who has had his ears pounded for hundred (thousands?) of hours by DX
contest stations whilst trying to listen to a deep weak layer among the
cacophony of strong stations, I am very excited by what I'm hearing
regarding the field test of APF.

While tinkering with the details, Elecraft, please think hard about what
both Paul and Guy had to say. APF could be lots of things but it doesn't
have to be something with every degree of freedom variable. Nor does one
have to emulate every sound of every audio DSP from rigs past.

However, if APF can be implemented in such a way that the operator can
establish a *persistent* setting that-for him or her-reduces the fatigue of
concentrating on the CW "noise," such capability would improve the K3.
Having the exact setting as the MP that Guy references? Not necessarily.
Having the same result? It sure would be of value to my (aging) ears. And
I would most likely use that persistent setting for all CW operation, casual
or competitive.

Gary W2CS

> From W9AC:
> I suspect the moment variable Q were to become available, soon thereafter,
> the next request would be for variable peaking amplitude. At some point,
> Elecraft must decide what they want from APF -- is it an emulation of a
> filter used in a transceiver from twenty years ago? Or, is it something
> more? If it's more, then it may as well be a full-blown parametric EQ
> channel with variable amplitude, variable frequency, and variable Q.
>
> >> From K2AV:
> >> 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.
> >>

Jeff Cochrane - VK4XA

K3 APF

CONTENTS DELETED

The author has deleted this message.

KK7P

Re: K3 APF

The APF has a rapid 180 degree phase shift as you pass through its
center frequency. This is fine fore CW, but would wreak havoc on a
PSK31 signal. The K3s narrow filters (nomianl 50 Hz) are very good for
local PSK31 decoding. In addition, most PC-based software includes
well-matched filters for PSK31 decoding.

The APF is really intended for CW operation only.

73,

Lyle KK7P

> What are the pro's and cons of implementing it for the digital modes too?

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AC7AC

Re: K3 APF Adjustable Q

In reply to this post by P.B. Christensen

CONTENTS DELETED

The author has deleted this message.

Jeff Cochrane - VK4XA

Re: K3 APF

In reply to this post by KK7P

CONTENTS DELETED

The author has deleted this message.

Kok Chen

Re: K3 APF

In reply to this post by Jeff Cochrane - VK4XA

On Oct 31, 2010, at 6:13 PM, Jeff Cochrane - VK4BOF wrote:

> I know nothing of CW and it's esoterics but it seems to me that maybe this APF thingy maybe of some use to digital signals too, as in peaking up a (very) weak PSK31 signal or something of that nature.
> Would that be the case?

IMHO, no.

Any PSK31 demodulator worth its salt should already have a matched filter (filter response matched to the keying sidebands of a PSK31 signal). Applying any shaper filter will just raise the bit error rate. The same is true if you use an APF that is sharper than what is determined by the rise and fall times of a CW keying waveform (i.e., increasing the Q of the AFP beyond a certain point will reduce the SNR of a CW signal).

In terms of other digital signals, you definitely don't want to apply any filtering ahead of an MFSK signal (MFSK16, DominoEX, etc), since the filter for each tone in those modes are already optimal (sin(x)/s) in shape because everybody uses FFTs to demodulate amateur MFSK.

In the RTTY world, "twin peak filters" available in many rigs often give better results only because many software demodulators do not come with matched filters. If you apply a twin peak filter in front of an RTTY demodulator that already has matched filtering that is matched to the RTTY baud rate, you will also degrade print on RTTY signals that have poor SNR and no adjacent channel QRM. Try that with RITTY (an MS-DOS program by K6STI) and cocoaModem, for example -- those are known to use matched filtering.

73
Chen, W7AY

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P.B. Christensen

Re: K3 APF

> "In the RTTY world, "twin peak filters" available in many rigs often give
> better results only because many software demodulators do not come with
> matched filters. "

Chen,

So far, nobody has discussed the possibility of an "Auto APF" feature that
functions much like Auto Notch, but would automatically track the peaking
frequency in the event RIT was engaged, for example. Within limits, such a
function would allow for hands free APF as the received pitch is changed by
the operator. Consider an automatic DSP notch filter that uses the LMS
algorithm. It seems that APF is really the inverse of the notch function.
Perhaps a quasi anti-LMS algorithm could be used to establish Auto APF.
Does such an algorithm now exit by name?

Paul, W9AC

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KK7P

Re: K3 APF

On the K3, that is the denoiser function.

73,

Lyle KK7P

> ...Consider an automatic DSP notch filter that uses the LMS
> algorithm. It seems that APF is really the inverse of the notch function.
> Perhaps a quasi anti-LMS algorithm could be used to establish Auto APF.
> Does such an algorithm now exit by name?

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Joe Subich, W4TV-4

Re: K3 APF

In reply to this post by P.B. Christensen

Paul,

>> It seems that APF is really the inverse of the notch function.
>> Perhaps a quasi anti-LMS algorithm could be used to establish Auto
>> APF.

That's exactly the CW noise reduction algorithm. I've seen Lyle write
many times that the NR builds a low order filter around any coherent
signal in the passband. For an "auto-APF" I'm sure the issue would be
to decide *which* coherent signal to build the filter for.

73,

... Joe, W4TV

On 10/31/2010 10:54 PM, Paul Christensen wrote:

>> "In the RTTY world, "twin peak filters" available in many rigs often give
>> better results only because many software demodulators do not come with
>> matched filters. "
>
> Chen,
>
> So far, nobody has discussed the possibility of an "Auto APF" feature that
> functions much like Auto Notch, but would automatically track the peaking
> frequency in the event RIT was engaged, for example. Within limits, such a
> function would allow for hands free APF as the received pitch is changed by
> the operator. Consider an automatic DSP notch filter that uses the LMS
> algorithm. It seems that APF is really the inverse of the notch function.
> Perhaps a quasi anti-LMS algorithm could be used to establish Auto APF.
> Does such an algorithm now exit by name?
>
> Paul, W9AC
>
> ______________________________________________________________
> 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
>

Kok Chen

Re: K3 APF

In reply to this post by P.B. Christensen

On Oct 31, 2010, at 7:54 PM, Paul Christensen wrote:

> Perhaps a quasi anti-LMS algorithm could be used to establish Auto APF.
> Does such an algorithm now exi[s]t by name?

(For those who are not familiar with "LMS," it was an algorithm created by Ted Hoff for his dissertation, under the supervision of Bernie Widrow. Hoff went on later to design the instruction set for a chip which became the Intel 4004, the first microprocessor. Many people know of Hoff as the inventor of the microprocessor, but fewer know him as the inventor of LMS.)

I really like your idea of experimenting with an auto APF that borrows from auto-notch algorithms.

I think you can experiment with auto-notching very low SNR carriers to see if existing LMS algorithms work well enough to use as the core of an APF circuit. I suspect though, that you *might* need a halfway decent SNR to notch well (or fast enough). This is not a problem with existing auto notchers since they are seldom, if ever, called on to notch away carriers that are right at the noise level.

If you can consistently and quickly auto-notch low-SNR carriers, then I think you are spot [sic] on Paul -- an LMS tracked auto APF when RIT is engaged!

If auto-notch does not work well notching low SNR carriers, then the existing auto-notch algorithm will probably also not work well as an APF peek-seeker. I suspect that bin averaging FFTs might be better for finding the location to peak. You trade off lots of processor cycles, of course.

If you look at the APF, I think it is really perfectly matched for aural reception. The typical APF is very sharp (no "flat top" portion at all in the frequency response), but the skirts are quite wide and monotonic. This allows one to hear a signal even when it is far from the peak. And since it is monotonic, you just keep turning the knob until the signal is the loudest, knowing that you are turning the knob in the correct direction as long as the tone is getting louder.

Pretty much the only thing you need to be careful about with high-Q digital IIR filter structures is avoiding the "limit cycle" problem (very low amplitude, periodic output when there is no input, caused by numerical truncation errors).

73
Chen, W7AY

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Bob K6UJ

Re: K3 APF Adjustable Q

In reply to this post by Guy, K2AV

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

Jim Brown-10

Re: K3 APF Adjustable Q

In reply to this post by Kok Chen

On 10/31/2010 11:44 AM, Kok Chen wrote:
> The same SNR argument applies to how noisy his local RF environment is
> compared to your environment

This is often the dominant factor. When I lived in a Chicago
residential neighborhood, my S-meter rarely got below S7 on band noise
with narrow CW filters. Here in the Santa Cruz Mountains, it's often
more like S3. If you assume 4 dB per S-unit (typical for most radios),
that's 16 dB. That means if the other guy has that S7 noise level, I've
got to run 1,000 watts to be heard as well as I would hear 25 watts from
him.

73, Jim K9YC
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David Woolley (E.L)

Re: K3 APF Adjustable Q

In reply to this post by Kok Chen

Quote para 2, both points: Reciprocity still applies with respect to
gain and off axis effects. If the receive antenna is down by 3dB, it
will be down by 3dB EIRP when transmitting; if down by 10dB, the EIRP
will be down 10dB.

Quote para 3: Local noise does make a real difference and will
compromise reciprocity.

Top quoted only by list policy.

Kok Chen wrote:
> Although Reciprocity Theory states that if both of you use the same
> power, the received power at the two antenna terminals will be the same
> independent of what antennas are at each end, other things determine if
> he can copy you better than you can copy him.

> However, another factor, arguably more important, is the antennas'
> directivity and where the directivity are aimed at. If his antenna is
> more directive than yours by 3 dB, all else being equal, he has a 3 dB
> of SNR advantage. If the arrival angle of his signal at your antenna is
> 10 dB below where your antenna actually peaks, while your signal arrives
> at his antenna where the response of his antenna peaks, you have yet
> another 10 dB disadvantage, etc.

> The same SNR argument applies to how noisy his local RF environment is
> compared to your environment.

--
David Woolley
"we do not overly restrict the subject matter on the list, and we
encourage postings on a wide range of amateur radio related topics"
List Guidelines <http://www.elecraft.com/elecraft_list_guidelines.htm>
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The Smiths

Re: K3 APF Adjustable Q

In reply to this post by Joe Subich, W4TV-4

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
> >
> > ______________________________________________________________
> > 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
> >
> ______________________________________________________________
> 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

The Smiths

Re: K3 APF Adjustable Q

In reply to this post by Steve Ellington

I vote to have both. I find that moving the Fc off center from my IF helps reduce the ringing that I get. I think you should give that a try Steve. Keep your IF center (SHIFT) then after you have used the CWT (or your ear) to tune someone in, drop their town down 20Hz, now activate the APF, then move the APF -20Hz, you'll not only peak their signal, but you'll also have reduced a lot of the ringing noise that you would normally get sitting in the center of the IF passband. This is argument to KEEP the Fc knob. Now, if you choose to keep your APF centered on the Pitch center (IF Center, passband center) than I believe that the variable Q would be very handy as well. So looks like that's argument for BOTH.. Not one or the other.

> From: [hidden email]
> To: [hidden email]; [hidden email]
> Date: Sun, 31 Oct 2010 08:58:57 -0400
> CC: [hidden email]
> Subject: Re: [Elecraft] K3 APF Adjustable Q
>
> 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
>
> ______________________________________________________________
> 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

The Smiths

Re: K3 APF Adjustable Q

In reply to this post by Guy, K2AV

100% agreed. Where it is now is perfect for the narrowest position.. a little adjustment to open it up for different conditions is what the doctor ordered. No one suffers anything so long as they keep it where THEY feel fit to.
Maybe this is a mistake in understanding that some people are having.. No one is asking that the current Q setting be made wider when it becomes variable, we're asking that it stays the same, but has the ability to open up a little too...

> Date: Sun, 31 Oct 2010 12:03:28 -0400
> From: [hidden email]
> To: [hidden email]
> CC: [hidden email]
> Subject: Re: [Elecraft] K3 APF Adjustable Q
>
> 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 <[hidden email]> 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" <[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
> >>>
> >>> ______________________________________________________________
> >>> 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
> >>>
> >> ______________________________________________________________
> >> 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
> >
> > ______________________________________________________________
> > 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
> >
> ______________________________________________________________
> 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

Philippe Trottet

Re: K3 APF Adjustable Q

In reply to this post by The Smiths

I agree with the comments about the use of the DPB filter who act as a APF with wider Q.
May be the suggestion is to give more "flexibility" to the DBP filter in order to let the K3 user choosing what would be the best in its own suppressing noise environment.
73's
Philippe A65BI

>>> The Smiths <[hidden email]> 01-11-2010 12:24 >>>

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...

______________________________________________________________
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Post: mailto:[hidden email]

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Joe Subich, W4TV-4

Re: K3 APF Adjustable Q

In reply to this post by The Smiths

>> 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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