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K3: CW weak signal

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Ken817821

K3: CW weak signal

When on low bands, weak signal, rf gain cranked up, narrow CW bandwidth, I get a bit of continuous howling effect from the white noise/QRN that is about the same audio freq as the signal I am copying.

I have .2 khz, 5 pole -.94 crystal.

I have always just ignored it, turning rf gain down helps a bit - very critical. But I started thinking maybe others have found some good techniques to minimize this. As I write this I think I may experiment with the boost I give for this crystal. Wondering if 8 pole crystals sound diferent.

Any suggestions?

Ken K5WK

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Ted Roycraft

Re: K3: CW weak signal

Hi Ken,

For narrow DSP filter bandwidths (100 Hz or less I think) you have the
option of using a FIR filter (default) or an IIR filter. IIR filters
can "ring" which sounds like it might be what you are experiencing.
That may be your problem - that you are using an IIR filter. You can
toggle between the FIR and IIR filters by a CONFIG command; CONFIG->FLx
BW (then tap 7). (See page 55 of the K3 manual under FLx BW.) Hope
that helps.

73, Ted, W2ZK

Kenneth Waites wrote:

> When on low bands, weak signal, rf gain cranked up, narrow CW bandwidth, I get a bit of continuous howling effect from the white noise/QRN that is about the same audio freq as the signal I am copying.
>
> I have .2 khz, 5 pole -.94 crystal.
>
> I have always just ignored it, turning rf gain down helps a bit - very critical. But I started thinking maybe others have found some good techniques to minimize this. As I write this I think I may experiment with the boost I give for this crystal. Wondering if 8 pole crystals sound diferent.
>
> Any suggestions?
>
> Ken K5WK
>
>
> ______________________________________________________________
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>

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KK7P

Re: K3: CW weak signal

> For narrow DSP filter bandwidths (100 Hz or less I think) you have the
> option of using a FIR filter (default) or an IIR filter. IIR filters
> can "ring" which sounds like it might be what you are experiencing.

The use of IIR filters is deprecated. The K3 defaults to FIR filters
and we encourage you to use them.

73,

Lyle KK7P

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M0XDF

Re: K3: CW weak signal

I don't quite understand that - is there some option which allows you
to choose?
73 de M0XDF, K3 #174

On 10 Nov 2009, at 18:24, Lyle Johnson wrote:

>> For narrow DSP filter bandwidths (100 Hz or less I think) you have
>> the
>> option of using a FIR filter (default) or an IIR filter. IIR filters
>> can "ring" which sounds like it might be what you are experiencing.
>
> The use of IIR filters is deprecated. The K3 defaults to FIR filters
> and we encourage you to use them.

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KK7P

Re: K3: CW weak signal

Hello David!

> I don't quite understand that - is there some option which allows you
> to choose?

Yes, please see page 24 of the manual "Narrow DSP FIlter Types" for details.

73,

Lyle KK7P

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Brendan Minish

Re: K3: CW weak signal

In reply to this post by KK7P

On Tue, 2009-11-10 at 10:24 -0800, Lyle Johnson wrote:

> The use of IIR filters is deprecated. The K3 defaults to FIR filters
> and we encourage you to use them.

For some conditions the slight ringing with the IIR filters can be a
real help, a bit like the effect that you can induce on some rigs with a
narrow APF filter.
I find that the IIR filters are often better than the FIR filters for
moderate speed CW on a very noisy band like 160m.
They may not be the best all-round choice but they do have their good
points.

--
73
Brendan EI6IZ

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M0XDF

Re: K3: CW weak signal

In reply to this post by KK7P

Thanks - time for a manual re-read :-(
73 de M0XDF, K3 #174
--
In theory, there is no difference between theory and practice,
but in practice there is.

On 10 Nov 2009, at 20:07, Lyle Johnson wrote:

> Hello David!
>
>> I don't quite understand that - is there some option which allows you
>> to choose?
>
> Yes, please see page 24 of the manual "Narrow DSP FIlter Types" for
> details.
>
> 73,
>
> Lyle KK7P
>
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Gary NL7Y

Re: K3: CW weak signal

In reply to this post by Ken817821

Low band DX from Interior Alaska are always a work in progress. Ignore the howling and instead listen for the signal. It's not a wolf at the door. Try this for weak DX:

200Hz filter (or the narrowest you have)
6-8db filter gain (weigh S/N vs signal strength - I set mine at 8db gain for weak, lower for stronger)
BW 100-0.50 Hz (any wider is worse for weak signals for me)
Pre-Amp on (it does help and does not distort the signal)
NB as required (I need DSP 2-7, IF Med-7, = 2S units lower city noise)
AGC Threshold 006 for weak signals, 005 for stronger signals if AGC on
AGC Slope 000, 005 for stronger signals if AGC on
Also try AGC Off and ride the RF gain for best signal
Adjust audio gain for minimum noise/best signal

You truly haven't experienced the unique abilities of the K3 until you work Low Band DX in, or just out of the the noise floor, compared with other radios. It's an amazing piece of radio gear.

73 Gary NL7Y

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Steve Ellington

Re: K3: CW weak signal

Gary: RE: Preamp ON

I agree with your comment on the preamp even though it runs against common
knowledge. Even on 160m where the noise level is S9, sometimes I can bring
out a weak cw signal by using the preamp and with AGC settings similar to
yours. I know it doesn't make sense and I can't explain it but it works.

Steve
N4LQ
[hidden email]
----- Original Message -----
From: "Gary NL7Y" <[hidden email]>
To: <[hidden email]>
Sent: Thursday, November 12, 2009 2:51 AM
Subject: Re: [Elecraft] [K3] K3: CW weak signal

>
> Low band DX from Interior Alaska are always a work in progress. Ignore the
> howling and instead listen for the signal. It's not a wolf at the door.
> Try
> this for weak DX:
>
> 200Hz filter (or the narrowest you have)
> 6-8db filter gain (weigh S/N vs signal strength - I set mine at 8db gain
> for
> weak, lower for stronger)
> BW 100-0.50 Hz (any wider is worse for weak signals for me)
> Pre-Amp on (it does help and does not distort the signal)
> NB as required (I need DSP 2-7, IF Med-7, = 2S units lower city noise)
> AGC Threshold 006 for weak signals, 005 for stronger signals if AGC on
> AGC Slope 000, 005 for stronger signals if AGC on
> Also try AGC Off and ride the RF gain for best signal
> Adjust audio gain for minimum noise/best signal
>
> You truly haven't experienced the unique abilities of the K3 until you
> work
> Low Band DX in, or just out of the the noise floor, compared with other
> radios. It's an amazing piece of radio gear.
>
> 73 Gary NL7Y
>
>
>
> _____________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
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> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>
>
>
> --
> View this message in context:
> http://n2.nabble.com/K3-CW-weak-signal-tp3981344p3991230.html
> Sent from the [K3] mailing list archive at Nabble.com.
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--------------------------------------------------------------------------------

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14:41:00

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Doug Turnbull

Re: K3: CW weak signal

Gary,
Thank you very much for this information - I will give it a try. This forum is a joy as is the K3.

73 Doug EI2CN

On Thu, 12 Nov 2009 08:17:27 -0500, "Steve Ellington" <[hidden email]> wrote:

> Gary: RE: Preamp ON
>
> I agree with your comment on the preamp even though it runs against common
> knowledge. Even on 160m where the noise level is S9, sometimes I can bring
> out a weak cw signal by using the preamp and with AGC settings similar to
> yours. I know it doesn't make sense and I can't explain it but it works.
>
> Steve
> N4LQ
> [hidden email]
> ----- Original Message -----
> From: "Gary NL7Y" <[hidden email]>
> To: <[hidden email]>
> Sent: Thursday, November 12, 2009 2:51 AM
> Subject: Re: [Elecraft] [K3] K3: CW weak signal
>
>
>>
>> Low band DX from Interior Alaska are always a work in progress. Ignore
> the
>> howling and instead listen for the signal. It's not a wolf at the door.
>> Try
>> this for weak DX:
>>
>> 200Hz filter (or the narrowest you have)
>> 6-8db filter gain (weigh S/N vs signal strength - I set mine at 8db gain
>> for
>> weak, lower for stronger)
>> BW 100-0.50 Hz (any wider is worse for weak signals for me)
>> Pre-Amp on (it does help and does not distort the signal)
>> NB as required (I need DSP 2-7, IF Med-7, = 2S units lower city noise)
>> AGC Threshold 006 for weak signals, 005 for stronger signals if AGC on
>> AGC Slope 000, 005 for stronger signals if AGC on
>> Also try AGC Off and ride the RF gain for best signal
>> Adjust audio gain for minimum noise/best signal
>>
>> You truly haven't experienced the unique abilities of the K3 until you
>> work
>> Low Band DX in, or just out of the the noise floor, compared with other
>> radios. It's an amazing piece of radio gear.
>>
>> 73 Gary NL7Y
>>
>>
>>
>> _____________________________________________________________
>> 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
>>
>>
>>
>> --
>> View this message in context:
>> http://n2.nabble.com/K3-CW-weak-signal-tp3981344p3991230.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
>
>
> --------------------------------------------------------------------------------
>
>
>
> No virus found in this incoming message.
> Checked by AVG - www.avg.com
> Version: 9.0.704 / Virus Database: 270.14.61/2497 - Release Date: 11/11/09
> 14:41:00
>
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drewko

Re: K3: CW weak signal

In reply to this post by Steve Ellington

Also, if you are using a KAT3 without separate receive antenna try
bypassing the ATU on receive. That can give you again as much
improvement in the MDS (minimum discernible signal) as switching the
preamp on.

Don't forget to switch in the ATU again when you go to transmit!

73,
Drew
AF2Z

On Thu, 12 Nov 2009 08:17:27 -0500,Steve N4LQ wrote:

Gary NL7Y

Re: K3: CW weak signal

In reply to this post by Gary NL7Y

Gary NL7Y wrote

Try this for weak DX:...Also try AGC Off and ride the RF gain for best signal

I posted this earlier, and after recalling these suggestions from the Contesting Compendium by Eric K3NA (http://wiki.contesting.com/index.php/Category:Setting_receiver_gain_controls) I tried them and found that the performance was very good indeed. His explanations of the setup makes it easy.

When implemented as suggested the RF gain effectively becomes a combined volume/RF gain control and weak DX often pops out of the noise. It's certainly worth a try.

73, Gary NL7Y