K3 -Advice: how to configure APF for least ringing

[RobertG]

As a 98% cw operator, I've explored the various K3 weak signal features.
I tend to shy away from the APF because its ringing seems to my ears to
be counter productive. Any advice/experience on how to set up and use
this feature for best results? Thanks.
...robert
--
Robert G Strickland, PhD ABPH - KE2WY
[hidden email]
Syracuse, New York, USA
______________________________________________________________
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

[Matt Zilmer]

Best used when copy any other way is impossible due to a weak signal.
Ringing is somewhat better than noise, isn't it?

I've found APF useful in a number of QRP events, when handling weak
signals is the order of the day.  Yes - copy may be dificult but at
least you have something to work with.  APF is similar to Q-mulipliers
we used in the 70's and earlier, prior to digital signal processing.

By memory, the K3's (and KX3's) APF is an order of magnitude better
than a Qmult.  Imho, it is mainly due to the excellent DSP work by
Lyle Johnson.  Of course, some of the difference is also due to the
relatively poor receivers we had back then.  

73,
matt W6NIA

On Fri, 10 May 2013 23:46:24 +0000, you wrote:

>As a 98% cw operator, I've explored the various K3 weak signal features.
>I tend to shy away from the APF because its ringing seems to my ears to
>be counter productive. Any advice/experience on how to set up and use
>this feature for best results? Thanks.
>...robert
______________________________________________________________
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

[Matt Zilmer]

I should have mentioned that APF is set the way it's set.  I don't
believe any parameters exist to change APF's operation.  Someone may
correct me on this.

APF is best used with a narrow bandwidth setting.  I think I saw the
figure 30 Hz (for -6dB points) used in conjunction with APF, so a 50
or 100 Hz filter setting seems in order.  That's what I use here.

73,
matt W6NIA

On Fri, 10 May 2013 17:33:35 -0700, you wrote:

>Best used when copy any other way is impossible due to a weak signal.
>Ringing is somewhat better than noise, isn't it?
>
>I've found APF useful in a number of QRP events, when handling weak
>signals is the order of the day.  Yes - copy may be dificult but at
>least you have something to work with.  APF is similar to Q-mulipliers
>we used in the 70's and earlier, prior to digital signal processing.
>
>By memory, the K3's (and KX3's) APF is an order of magnitude better
>than a Qmult.  Imho, it is mainly due to the excellent DSP work by
>Lyle Johnson.  Of course, some of the difference is also due to the
>relatively poor receivers we had back then.  
>
>73,
>matt W6NIA
>
>On Fri, 10 May 2013 23:46:24 +0000, you wrote:
>
>>As a 98% cw operator, I've explored the various K3 weak signal features.
>>I tend to shy away from the APF because its ringing seems to my ears to
>>be counter productive. Any advice/experience on how to set up and use
>>this feature for best results? Thanks.
>>...robert

______________________________________________________________
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

[Ed Stallman]

I work mostly CW weak signal and have not heard ringing with the K3 ..
Now I will say if you have your tones "CW Pitch" set at 800 Hz + or - it
may sound like ringing to you , you might try lowering the CW Pitch say
around 600 Hz or even lower

Ed N5DG






On 5/10/2013 7:36 PM, Matt Zilmer wrote:

> I should have mentioned that APF is set the way it's set.  I don't
> believe any parameters exist to change APF's operation.  Someone may
> correct me on this.
>
> APF is best used with a narrow bandwidth setting.  I think I saw the
> figure 30 Hz (for -6dB points) used in conjunction with APF, so a 50
> or 100 Hz filter setting seems in order.  That's what I use here.
>
> 73,
> matt W6NIA
>
> On Fri, 10 May 2013 17:33:35 -0700, you wrote:
>
>> Best used when copy any other way is impossible due to a weak signal.
>> Ringing is somewhat better than noise, isn't it?
>>
>> I've found APF useful in a number of QRP events, when handling weak
>> signals is the order of the day.  Yes - copy may be dificult but at
>> least you have something to work with.  APF is similar to Q-mulipliers
>> we used in the 70's and earlier, prior to digital signal processing.
>>
>> By memory, the K3's (and KX3's) APF is an order of magnitude better
>> than a Qmult.  Imho, it is mainly due to the excellent DSP work by
>> Lyle Johnson.  Of course, some of the difference is also due to the
>> relatively poor receivers we had back then.
>>
>> 73,
>> matt W6NIA
>>
>> On Fri, 10 May 2013 23:46:24 +0000, you wrote:
>>
>>> As a 98% cw operator, I've explored the various K3 weak signal features.
>>> I tend to shy away from the APF because its ringing seems to my ears to
>>> be counter productive. Any advice/experience on how to set up and use
>>> this feature for best results? Thanks.
>>> ...robert
> ______________________________________________________________
> 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

[donhall161]

I use 440 Hz and the APF almost full time, particularly for weak signal
work.

73  Don  K5AQ

______________________________________________________________
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

[Brian Hunt]

Here's another approach to using APF on weak signals in an uncrowded band.

- Turn on NR set to 5m3.  You can play with this but 5m3 seems to work
best here.
- Set the DSP bandwidth to 1 KHz.   This is a good way to search for
weak signals you can't hear otherwise.  The combination of NR and DSP BW
drops the uncorrelated noise many dB.
- Turn on the APF and carefully tune the signal to the peak of the APF
passband.  I typically use Spectrogram on a PC as a tuning aid
throughout this whole process.
- Ride the AF and RF gain controls to minimize the ringing affect

Happy hunting!

Brian, K0DTJ


______________________________________________________________
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

[Gary Hinson]

I use APF only as a last resort, Robert.  It can sometimes help me dig out
and record very weak 10m beacons under QRM from adjacent beacons, with CW
filters on turbo, sometimes also using the manual notch filter to try to
kill the worst QRM.  It takes time to peak the desired signal precisely on
the nose of the APF, using the fine tuning setting, the CWT function and
watching audio levels with the audio recording software (Audacity in my
case).   Beacons transmit continuously so there is no mad rush to get it set
up.  For regular DX QSOs, it's not worth the bother in my opinion, but as I
recall the APF facility was introduced in response to requests from 160m
DXers desperate to glean the faintest sniff of RF from the ionosphere.
 
It does indeed ring.  There is probably a physics lecturer desperate to tell
us that ringing is an inevitable consequence of the very tight filtering,
plus artifacts from the digital processing I guess.  Ringing gets worse with
fast CW but beacons tend to send quite slowly.

73
Gary   ZL2iFB

> -----Original Message-----
> From: [hidden email] [mailto:elecraft-
> [hidden email]] On Behalf Of Robert G Strickland
> Sent: Saturday, 11 May 2013 11:46 a.m.
> To: Elecraft
> Subject: [Elecraft] K3 -Advice: how to configure APF for least ringing
>
> As a 98% cw operator, I've explored the various K3 weak signal features.
> I tend to shy away from the APF because its ringing seems to my ears to be
> counter productive. Any advice/experience on how to set up and use this
> feature for best results? Thanks.
> ...robert
> --
> Robert G Strickland, PhD ABPH - KE2WY
> [hidden email]
> Syracuse, New York, USA
> __________________________________________________________
> ____
> 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

--
This message has been scanned for viruses and
dangerous content by MailScanner, and is
believed to be clean.

______________________________________________________________
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]

RobertG wrote

I tend to shy away from the APF because its ringing seems to my ears to
be counter productive. Any advice/experience on how to set up and use
this feature for best results?

If you don't use APF you're missing one of the best features of the K3 for weak signals.  I now use it nearly 100% of the time for QRP SOTA stations on the higher bands or DX on 160m.  There are two keys for me to using it effectively:

1.  Back off RF Gain until the signal is at the noise floor.  If you have too much signal, you'll definitely create ringing.

2.  Use a relatively wide DSP/XFIL setting (e.g. I often use DSP=400 Hz with a 200 Hz XFIL, yes I set the 200 Hz XFIL to enable at 400 Hz instead of 200 Hz).  In 160 contests, I sometimes use DSP=600 in a 500 Hz XFIL to better hear off-frequency callers).  The relatively wider noise passband helps my ears distinguish signal from noise and APF then greatly improves this ability.

73,  Bill  W4ZV

P.S.  It goes without saying to carefully peak the APF on signal! (10 Hz steps maximum or even lower for extremely weak signals).