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Dave ne5dl

APF

Did anything change with APF in the latest release ? Seemed to perform
better before rev 2.45. Maybe I 'm just loosing my touch.

73 Dave Lear NE5DL

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juergen piezo

Re: APF

Hi Dave

I asked the same question.

The gurus at Elecraft indicated that nothing had changed. I still have the original firmware and load it up in my spare K3. The original version is the ESP version that works for me.

I like you cant get the same results with the current release of the APF that I go with the original. The original blew my socks off I was so impressed with it. I have done the comparison test so many times now that I know that the original was the better release and its not my imagination.

If the programmer says the hex code is the same then there must be some other factors at play. I dont really have the answer. I am keeping the original firmware just for contests.

73
John

--- On Wed, 1/26/11, David Lear <[hidden email]> wrote:

> From: David Lear <[hidden email]>
> Subject: [Elecraft] APF
> To: [hidden email]
> Date: Wednesday, January 26, 2011, 11:27 AM
> Did anything change with APF in the
> latest release ? Seemed to perform
> better before rev 2.45. Maybe I 'm just loosing my touch.
>
> 73 Dave Lear NE5DL
>
> ______________________________________________________________
> 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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Dr. Detlef Petrausch

Re: APF

Hi John,

I agree with you.

73 Detlef, DL7NDF

Am 26.01.2011 21:19, schrieb juergen:

> Hi Dave
>
> I asked the same question.
>
> The gurus at Elecraft indicated that nothing had changed. I still have the original firmware and load it up in my spare K3. The original version is the ESP version that works for me.
>
> I like you cant get the same results with the current release of the APF that I go with the original. The original blew my socks off I was so impressed with it. I have done the comparison test so many times now that I know that the original was the better release and its not my imagination.
>
> If the programmer says the hex code is the same then there must be some other factors at play. I dont really have the answer. I am keeping the original firmware just for contests.
>
> 73
> John
>
>
>
> --- On Wed, 1/26/11, David Lear<[hidden email]> wrote:
>
>> From: David Lear<[hidden email]>
>> Subject: [Elecraft] APF
>> To: [hidden email]
>> Date: Wednesday, January 26, 2011, 11:27 AM
>> Did anything change with APF in the
>> latest release ? Seemed to perform
>> better before rev 2.45. Maybe I 'm just loosing my touch.
>>
>> 73 Dave Lear NE5DL
>>
>> ______________________________________________________________
>> 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
>
>

Barry N1EU

Re: APF

In reply to this post by juergen piezo

Okay, what version of firmware has the "original" APF that worked better for you guys? I'll try and run a spectral comparison of the two and post the results. I'm skeptical that there's a difference but I'm willing to give it a go.

Barry N1EU

juergen piezo wrote

I like you cant get the same results with the current release of the APF that I go with the original.

wayne burdick

Re: APF

Administrator

In reply to this post by juergen piezo

Gents,

Even *I* thought something had changed. (Lyle, our DSP engineer,
assured me that it hadn't. The code hasn't changed.)

What's happening is that APF's effect is more obvious in the presence
of certain band-noise conditions. These conditions will vary from band
to band, and can change hourly, daily, maybe even monthly for a given
QTH. I went back and listened the next day, and the APF was doing its
job. I find it especially useful on the low bands, and many K3 owners
have posted testimonials about this -- using the final version of the
code.

The APF algorithm, with its gradual slope and ~30 Hz wide peak, brings
up a very narrow portion of the audio spectrum (around the center
pitch) just a few dB, without bringing up the adjacent noise or
causing a rapid phase transition.

On several occasions I've measured a 3 to 5 dB improvement in S+N/N on
weak signals using the K3's built-in audio voltmeter.

73,
Wayne
N6KR

On Jan 26, 2011, at 12:19 PM, juergen wrote:

> Hi Dave
>
> I asked the same question.
>
> The gurus at Elecraft indicated that nothing had changed. I still
> have the original firmware and load it up in my spare K3. The
> original version is the ESP version that works for me.
>
> I like you cant get the same results with the current release of the
> APF that I go with the original. The original blew my socks off I
> was so impressed with it. I have done the comparison test so many
> times now that I know that the original was the better release and
> its not my imagination.
>
> If the programmer says the hex code is the same then there must be
> some other factors at play. I dont really have the answer. I am
> keeping the original firmware just for contests.
>
> 73
> John
>
>
>
> --- On Wed, 1/26/11, David Lear <[hidden email]> wrote:
>
>> From: David Lear <[hidden email]>
>> Subject: [Elecraft] APF
>> To: [hidden email]
>> Date: Wednesday, January 26, 2011, 11:27 AM
>> Did anything change with APF in the
>> latest release ? Seemed to perform
>> better before rev 2.45. Maybe I 'm just loosing my touch.
>>
>> 73 Dave Lear NE5DL
>>
>> ______________________________________________________________
>> 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

Steve Ellington

Re: APF

In reply to this post by Barry N1EU

Barry
>From what I can tell. MCU 4.21/DSP 2.69/ etc. is when APF first appeared.
I had the same experience. In fact, I was actually leaving APF on most of
the time until the newer version came along. I loved it......Now I seldom
use it because it does more harm than good.
Maybe one's socks can only be blown off once?
Steve
N4LQ
----- Original Message -----
From: "Barry N1EU" <[hidden email]>
To: <[hidden email]>
Sent: Wednesday, January 26, 2011 6:12 PM
Subject: Re: [Elecraft] APF

>
> Okay, what version of firmware has the "original" APF that worked better
> for
> you guys? I'll try and run a spectral comparison of the two and post the
> results. I'm skeptical that there's a difference but I'm willing to give
> it
> a go.
>
> Barry N1EU
>
>
> juergen piezo wrote:
>>
>> I like you cant get the same results with the current release of the APF
>> that I go with the original.
>>
>
> --
> View this message in context:
> http://elecraft.365791.n2.nabble.com/APF-tp5963894p5964585.html
> Sent from the [K3] mailing list archive at Nabble.com.
> ______________________________________________________________
> 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

Barry N1EU

Re: APF

Forget it - full stop!

I just ran a spectral analysis of the current firmware versus the very first APF implementation (mcu 4.17 dsp 2.65) from 11/3/10 AND THE PLOTS ARE ABSOLUTELY CONGRUOUS! The APF implementation hasn't changed a bit (or a byte).

Have a look: http://n1eu.com/k3apf.gif

magenta and green plots are taken with width = 200hz
aqua and yellow plots are taken with width = 100hz

Barry N1EU

Guy, K2AV

Re: APF

May I suggest that one of the necessities of using APF is to throttle back
the RF gain so that the AGC is not pushing up the noise to the level of
forcing what sounds like ringing. When I'm hearing what sounds like
ringing, moving back the RF gain (or removing PRE, or using ATT) will
usually clear it up. Using slow AGC usually does NOT help much, but backing
off RF gain so the background noise is only moderate or less usually helps.

73, Guy.

On Wed, Jan 26, 2011 at 6:52 PM, Barry N1EU <[hidden email]> wrote:

>
> Forget it - full stop!
>
> I just ran a spectral analysis of the current firmware versus the very
> first
> APF implementation (mcu 4.17 dsp 2.65) from 11/3/10 AND THE PLOTS ARE
> ABSOLUTELY CONGRUOUS! The APF implementation hasn't changed a bit (or a
> byte).
>
> Have a look: http://n1eu.com/k3apf.gif
>
> magenta and green plots are taken with width = 200hz
> aqua and yellow plots are taken with width = 100hz
>
> Barry N1EU
> --
> View this message in context:
> http://elecraft.365791.n2.nabble.com/APF-tp5963894p5964669.html
> Sent from the [K3] mailing list archive at Nabble.com.
> ______________________________________________________________
> 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
>

Bob K6UJ

Re: APF

In reply to this post by juergen piezo

John,
What is the firmware version number of the earlier one that the APF worked the best ?
I'm thinking about trying the APF out in this version.

thanks,
Bob
K6UJ

On Jan 26, 2011, at 12:19 PM, juergen wrote:

> Hi Dave
>
> I asked the same question.
>
> The gurus at Elecraft indicated that nothing had changed. I still have the original firmware and load it up in my spare K3. The original version is the ESP version that works for me.
>
> I like you cant get the same results with the current release of the APF that I go with the original. The original blew my socks off I was so impressed with it. I have done the comparison test so many times now that I know that the original was the better release and its not my imagination.
>
> If the programmer says the hex code is the same then there must be some other factors at play. I dont really have the answer. I am keeping the original firmware just for contests.
>
> 73
> John
>
>
>
> --- On Wed, 1/26/11, David Lear <[hidden email]> wrote:
>
>> From: David Lear <[hidden email]>
>> Subject: [Elecraft] APF
>> To: [hidden email]
>> Date: Wednesday, January 26, 2011, 11:27 AM
>> Did anything change with APF in the
>> latest release ? Seemed to perform
>> better before rev 2.45. Maybe I 'm just loosing my touch.
>>
>> 73 Dave Lear NE5DL
>>
>> ______________________________________________________________
>> 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

Bob K6UJ

Re: APF

In reply to this post by Barry N1EU

Hi Barry,
I'm curious too. This has come up before. I'd be interested in what you
see.

73,
Bob
K6UJ

On Jan 26, 2011, at 3:12 PM, Barry N1EU wrote:

>
> Okay, what version of firmware has the "original" APF that worked better for
> you guys? I'll try and run a spectral comparison of the two and post the
> results. I'm skeptical that there's a difference but I'm willing to give it
> a go.
>
> Barry N1EU
>
>
> juergen piezo wrote:
>>
>> I like you cant get the same results with the current release of the APF
>> that I go with the original.
>>
>
> --
> View this message in context: http://elecraft.365791.n2.nabble.com/APF-tp5963894p5964585.html
> Sent from the [K3] mailing list archive at Nabble.com.
> ______________________________________________________________
> 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

Arie Kleingeld PA3A-2

APF measurements: FW 4.17 better results by 2 dB

In reply to this post by Barry N1EU

Hello all,

Did some measurements on the different frimware versions. This time not
a BW-plot but I measured S+N/N ratio's.

I have no lab equipment but I have a K3 with dBV measurements, XG2 and
the stepped attenuator from elecraft.
I measured the difference of the K3 dBV-reading in signal off (=N) and
signal on (=S+N)
AGC off, mode CW, 400Hz BW and 400Hz Roofing.
RX gain of the K3 has been calibrated with XG2 and the K3 utility.

This is what I found.

_FW 4.25 and 4.21 (both give the same measurement values):_
At MDS level (stepped att on 20dB to reach this level)
normal 400 Hz BW: S+N/N = 3dB (as expected, hi)
400 Hz BW + dual PB: S+N/N = 10 dB

Now signal level 6dB under MDS (26dB att instead of 20dB):
normal 400 Hz BW: S+N/N = 0.5 dB
400 Hz BW + dual PB: S+N/N = 4 dB

_FW 4.17_
At MDS level (stepped att on 20dB)
normal 400 Hz BW: S+N/N = 3dB (as expected)
400 Hz BW + dual PB: S+N/N = 12 dB (THIS is 2 dB BETTER)

Now signal level 6dB under MDS:
normal 400 Hz BW: S+N/N = 0.5 dB
400 Hz BW + dual PB: S+N/N = 6 dB (THIS is 2dB BETTER)

There are probably people that can measure this far more better than I
did with better equipment.
But this is what I can come up with here.

73,
Arie PA3A

Op 27-1-2011 0:52, Barry N1EU schreef:

> Forget it - full stop!
>
> I just ran a spectral analysis of the current firmware versus the very first
> APF implementation (mcu 4.17 dsp 2.65) from 11/3/10 AND THE PLOTS ARE
> ABSOLUTELY CONGRUOUS! The APF implementation hasn't changed a bit (or a
> byte).
>
> Have a look: http://n1eu.com/k3apf.gif
>
> magenta and green plots are taken with width = 200hz
> aqua and yellow plots are taken with width = 100hz
>
> Barry N1EU

Arie Kleingeld PA3A-2

Re: APF measurements: FW 4.17 better results by 2 dB

All,
where I mentioned Dual PB, I mean ofcourse the APF, because that the
discussion here.

Sorry If that is not clear.
73
Arie PA3A

Op 27-1-2011 12:44, Arie Kleingeld PA3A schreef:

> Hello all,
>
> Did some measurements on the different frimware versions. This time not
> a BW-plot but I measured S+N/N ratio's.
>
>
> I have no lab equipment but I have a K3 with dBV measurements, XG2 and
> the stepped attenuator from elecraft.
> I measured the difference of the K3 dBV-reading in signal off (=N) and
> signal on (=S+N)
> AGC off, mode CW, 400Hz BW and 400Hz Roofing.
> RX gain of the K3 has been calibrated with XG2 and the K3 utility.
>
>
> This is what I found.
>
> _FW 4.25 and 4.21 (both give the same measurement values):_
> At MDS level (stepped att on 20dB to reach this level)
> normal 400 Hz BW: S+N/N = 3dB (as expected, hi)
> 400 Hz BW + dual PB: S+N/N = 10 dB
>
> Now signal level 6dB under MDS (26dB att instead of 20dB):
> normal 400 Hz BW: S+N/N = 0.5 dB
> 400 Hz BW + dual PB: S+N/N = 4 dB
>
>
> _FW 4.17_
> At MDS level (stepped att on 20dB)
> normal 400 Hz BW: S+N/N = 3dB (as expected)
> 400 Hz BW + dual PB: S+N/N = 12 dB (THIS is 2 dB BETTER)
>
> Now signal level 6dB under MDS:
> normal 400 Hz BW: S+N/N = 0.5 dB
> 400 Hz BW + dual PB: S+N/N = 6 dB (THIS is 2dB BETTER)
>
>
> There are probably people that can measure this far more better than I
> did with better equipment.
> But this is what I can come up with here.
>
> 73,
> Arie PA3A
>
>
>
> Op 27-1-2011 0:52, Barry N1EU schreef:
>> Forget it - full stop!
>>
>> I just ran a spectral analysis of the current firmware versus the very first
>> APF implementation (mcu 4.17 dsp 2.65) from 11/3/10 AND THE PLOTS ARE
>> ABSOLUTELY CONGRUOUS! The APF implementation hasn't changed a bit (or a
>> byte).
>>
>> Have a look: http://n1eu.com/k3apf.gif
>>
>> magenta and green plots are taken with width = 200hz
>> aqua and yellow plots are taken with width = 100hz
>>
>> Barry N1EU
> ______________________________________________________________
> 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
>

Bill W4ZV

Re: APF measurements: FW 4.17 better results by 2 dB

In reply to this post by Arie Kleingeld PA3A-2

Arie Kleingeld PA3A-2 wrote

I have no lab equipment but I have a K3 with dBV measurements, XG2 and
the stepped attenuator from elecraft.

Arie I believe you may have some measurement error. I'm sure you know that noise can only be measured correctly with a True RMS responding meter...which is not what is in the K3 dBV meter. This is the only way I can reconcile any difference based on N1EU's measurements:

> I just ran a spectral analysis of the current firmware versus the very first
> APF implementation (mcu 4.17 dsp 2.65) from 11/3/10 AND THE PLOTS ARE
> ABSOLUTELY CONGRUOUS! The APF implementation hasn't changed a bit (or a
> byte).
>
> Have a look: http://n1eu.com/k3apf.gif

If the APF filter responses are identical, your S/N measurements should also be identical.

http://vk1od.net/measurement/noise/multimeter.htm

"Conclusions

The model and the experimental results both suggest that these and similar multimeter are not capable of single high resolution relative measurements of narrowband audio noise such as measuring S/N ratios or Y factor for noise figure measurement due mainly to the short integration time in combination with narrow bandwidth.

It may be possible to improve resolution by taking multiple measurements and calculating the root of the mean of the squares of the measurements, but errors in the summary process and in temporal drift become an issue."

73, Bill

Scott Ellington

Re: APF measurements: FW 4.17 better results by 2 dB

Page 36 of the K3 owner's manual:

"AFV shows the true RMS value of receiver AF output (mVp-p), unaffected by AF GAIN control. "

73,

Scott K9MA

On Jan 27, 2011, at 1:17 PM, Bill W4ZV wrote:

> I'm sure you know that
> noise can only be measured correctly with a True RMS responding
> meter...which is not what is in the K3 dBV meter.

Scott Ellington
Madison, Wisconsin
USA

______________________________________________________________
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

Steve Ellington

Re: APF measurements: FW 4.17 better results by 2 dB

In reply to this post by Arie Kleingeld PA3A-2

FW pre-beta 4.16 release was actually the first to have APF, not 4.17.
Here's an interesting comment made shortly APF was finally released to the
public.
http://elecraft.365791.n2.nabble.com/K3-APF-td5735159.html#a5736718

Steve
N4LQ
----- Original Message -----
From: "Arie Kleingeld PA3A" <[hidden email]>
To: <[hidden email]>
Sent: Thursday, January 27, 2011 6:44 AM
Subject: [Elecraft] APF measurements: FW 4.17 better results by 2 dB

> Hello all,
>
> Did some measurements on the different frimware versions. This time not
> a BW-plot but I measured S+N/N ratio's.
>
>
> I have no lab equipment but I have a K3 with dBV measurements, XG2 and
> the stepped attenuator from elecraft.
> I measured the difference of the K3 dBV-reading in signal off (=N) and
> signal on (=S+N)
> AGC off, mode CW, 400Hz BW and 400Hz Roofing.
> RX gain of the K3 has been calibrated with XG2 and the K3 utility.
>
>
> This is what I found.
>
> _FW 4.25 and 4.21 (both give the same measurement values):_
> At MDS level (stepped att on 20dB to reach this level)
> normal 400 Hz BW: S+N/N = 3dB (as expected, hi)
> 400 Hz BW + dual PB: S+N/N = 10 dB
>
> Now signal level 6dB under MDS (26dB att instead of 20dB):
> normal 400 Hz BW: S+N/N = 0.5 dB
> 400 Hz BW + dual PB: S+N/N = 4 dB
>
>
> _FW 4.17_
> At MDS level (stepped att on 20dB)
> normal 400 Hz BW: S+N/N = 3dB (as expected)
> 400 Hz BW + dual PB: S+N/N = 12 dB (THIS is 2 dB BETTER)
>
> Now signal level 6dB under MDS:
> normal 400 Hz BW: S+N/N = 0.5 dB
> 400 Hz BW + dual PB: S+N/N = 6 dB (THIS is 2dB BETTER)
>
>
> There are probably people that can measure this far more better than I
> did with better equipment.
> But this is what I can come up with here.
>
> 73,
> Arie PA3A
>
>
>
> Op 27-1-2011 0:52, Barry N1EU schreef:
>> Forget it - full stop!
>>
>> I just ran a spectral analysis of the current firmware versus the very
>> first
>> APF implementation (mcu 4.17 dsp 2.65) from 11/3/10 AND THE PLOTS ARE
>> ABSOLUTELY CONGRUOUS! The APF implementation hasn't changed a bit (or a
>> byte).
>>
>> Have a look: http://n1eu.com/k3apf.gif
>>
>> magenta and green plots are taken with width = 200hz
>> aqua and yellow plots are taken with width = 100hz
>>
>> Barry N1EU
> ______________________________________________________________
> 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

Barry N1EU

Re: APF measurements: FW 4.17 better results by 2 dB

I'll check the APF in 4.16 after work and see if it's any different.

Barry N1EU

On Thu, Jan 27, 2011 at 7:58 PM, Steve Ellington [via Elecraft] <
[hidden email]<ml-node%[hidden email]>
> wrote:

> FW pre-beta 4.16 release was actually the first to have APF, not 4.17.
> Here's an interesting comment made shortly APF was finally released to the
> public.
> http://elecraft.365791.n2.nabble.com/K3-APF-td5735159.html#a5736718<http://elecraft.365791.n2.nabble.com/K3-APF-td5735159.html?by-user=t#a5736718>
>
>
>
> Steve
> N4LQ
> ----- Original Message -----
> From: "Arie Kleingeld PA3A" <[hidden email]<http://user/SendEmail.jtp?type=node&node=5967599&i=0>>
>
> To: <[hidden email] <http://user/SendEmail.jtp?type=node&node=5967599&i=1>>
>
> Sent: Thursday, January 27, 2011 6:44 AM
> Subject: [Elecraft] APF measurements: FW 4.17 better results by 2 dB
>
>
> > Hello all,
> >
> > Did some measurements on the different frimware versions. This time not
> > a BW-plot but I measured S+N/N ratio's.
> >
> >
> > I have no lab equipment but I have a K3 with dBV measurements, XG2 and
> > the stepped attenuator from elecraft.
> > I measured the difference of the K3 dBV-reading in signal off (=N) and
> > signal on (=S+N)
> > AGC off, mode CW, 400Hz BW and 400Hz Roofing.
> > RX gain of the K3 has been calibrated with XG2 and the K3 utility.
> >
> >
> > This is what I found.
> >
> > _FW 4.25 and 4.21 (both give the same measurement values):_
> > At MDS level (stepped att on 20dB to reach this level)
> > normal 400 Hz BW: S+N/N = 3dB (as expected, hi)
> > 400 Hz BW + dual PB: S+N/N = 10 dB
> >
> > Now signal level 6dB under MDS (26dB att instead of 20dB):
> > normal 400 Hz BW: S+N/N = 0.5 dB
> > 400 Hz BW + dual PB: S+N/N = 4 dB
> >
> >
> > _FW 4.17_
> > At MDS level (stepped att on 20dB)
> > normal 400 Hz BW: S+N/N = 3dB (as expected)
> > 400 Hz BW + dual PB: S+N/N = 12 dB (THIS is 2 dB BETTER)
> >
> > Now signal level 6dB under MDS:
> > normal 400 Hz BW: S+N/N = 0.5 dB
> > 400 Hz BW + dual PB: S+N/N = 6 dB (THIS is 2dB BETTER)
> >
> >
> > There are probably people that can measure this far more better than I
> > did with better equipment.
> > But this is what I can come up with here.
> >
> > 73,
> > Arie PA3A
> >
> >
> >
> > Op 27-1-2011 0:52, Barry N1EU schreef:
> >> Forget it - full stop!
> >>
> >> I just ran a spectral analysis of the current firmware versus the very
> >> first
> >> APF implementation (mcu 4.17 dsp 2.65) from 11/3/10 AND THE PLOTS ARE
> >> ABSOLUTELY CONGRUOUS! The APF implementation hasn't changed a bit (or a
>
> >> byte).
> >>
> >> Have a look: http://n1eu.com/k3apf.gif
> >>
> >> magenta and green plots are taken with width = 200hz
> >> aqua and yellow plots are taken with width = 100hz
> >>
> >> Barry N1EU
> > ______________________________________________________________
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> >
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> > Please help support this email list: http://www.qsl.net/donate.html
>
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Bill W4ZV

Re: APF measurements: FW 4.17 better results by 2 dB

In reply to this post by Scott Ellington

Scott Ellington wrote

Page 36 of the K3 owner's manual:

"AFV shows the true RMS value of receiver AF output (mVp-p), unaffected by AF GAIN control. "

While that may be true for sinusoidal signals I doubt it holds for noise measurements. Accurate noise measurements require a "true RMS-responding" meter...not a peak-responding or average-responding meter calibrated to display RMS for sinusoidal waves (only). Many DMMs throw around the term "true RMS" but are actually NOT true RMS-responding (which is required for accurate noise measurement). True RMS meters are much more expensive and will measure both sinusoidal and non-sinusoidal signals including noise. Most analog DMMS use thermocouples to determine the heating value (or energy content) of signals. There is a way to do true RMS with a DSP but would require a much wider bandwidth (i.e. higher sampling rate) than the K3 uses.

73, Bill

Arie Kleingeld PA3A-2

Re: APF measurements: FW 4.17 better results by 2 dB

In reply to this post by Bill W4ZV

Bill,

Thanks for your added comments.

As I said, I do not have the lab equipment to do this. But there are
people in this group that have and can measure far better than I.
The APF (for me) is not about selectivity. I use it when digging into
the noise and get a better copy of weak signals.
That is why I tried to measure S+N/N ratio the best I could. So if it is
not exactly 2 dB (it is not), I donot care. I just measured that there
was a _difference_ that 4.17 did a better job on s+n/n ratio.

So if one of the pro's can measure this more scientifically, that would
be very enlighting.

If this s+n/n ratio and the passband are the same, then we can stop this
discussion about the apf. :-)

73
Arie

>
> "Conclusions
>
> The model and the experimental results both suggest that these and similar
> multimeter are not capable of single high resolution relative measurements
> of narrowband audio noise such as measuring S/N ratios or Y factor for noise
> figure measurement due mainly to the short integration time in combination
> with narrow bandwidth.
>
> It may be possible to improve resolution by taking multiple measurements and
> calculating the root of the mean of the squares of the measurements, but
> errors in the summary process and in temporal drift become an issue."
>
> 73, Bill
>

KK7P

Re: APF measurements: FW 4.17 better results by 2 dB

In reply to this post by Bill W4ZV

Within the band-limited audio passband of the K3, the RMS metering is
very accurate. The algorithm is:

1) measure and square each reading
2) sum with the previous readings (accumulate)
3) do this for 500 ms or 1 sec
4) divide the sum by the number of samples taken
5) compute the square root
6) clear the accumulator

It tracked my HP 34401A to within 0.1 dB during measurements taken while
developing and validating the DSP code.

73,

Lyle KK7P

>> "AFV shows the true RMS value of receiver AF output (mVp-p), unaffected by
>> AF GAIN control. "
>>
> While that may be true for sinusoidal signals I doubt it holds for noise
> measurements... There is a way to do true RMS with a DSP but would
> require a much wider bandwidth (i.e. higher sampling rate) than the K3 uses.
>

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ab2tc

Re: APF measurements: FW 4.17 better results by 2 dB

In reply to this post by Bill W4ZV

Hi,

Doing true RMS over the selected passband is very easy to do with DSP and I have no reason to doubt that the K3 dBV meter is a very close approximation to true RMS even on signals that are far from sinusoidal (such as noise). Analog is a different story and I agree that there are many false claims to be "true RMS".

AB2TC - Knut

Bill W4ZV wrote

<snip>
While that may be true for sinusoidal signals I doubt it holds for noise measurements. Accurate noise measurements require a "true RMS-responding" meter...not a peak-responding or average-responding meter calibrated to display RMS for sinusoidal waves (only). Many DMMs throw around the term "true RMS" but are actually NOT true RMS-responding (which is required for accurate noise measurement). True RMS meters are much more expensive and will measure both sinusoidal and non-sinusoidal signals including noise. Most analog DMMS use thermocouples to determine the heating value (or energy content) of signals. There is a way to do true RMS with a DSP but would require a much wider bandwidth (i.e. higher sampling rate) than the K3 uses.

73, Bill