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Manual notch In K3

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Johnny Siu

Manual notch In K3

Hello Group,

I attempted to manual notch a strong carrier adjacent to a weak station.
Although I was able to notch out the strong carrier (from the audio), there was
no reduction in S meter level caused by that strong carrier. In other words,
the weak station did not pop out from the noise because the stronger
carrier de-sensed the K3 AGC.

Please advise whether my observation is correct.

TNX,

Johnny VR2XMC

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Arie Kleingeld PA3A-2

Re: Manual notch In K3

Johnny,

This is correct. Same experience here.

Although I would like that the notch would take the carrier out like a
conventional IF notch.

It has been said several times in the reflector that taking out the
carrier and increasing the gain again would degrade performance,
especially the dynamic range. If I do not reproduce this right, please
anyone in the group, please correct me.

What I think of this? I disagree strongly. Not on the IMD thing, I
cannot measure such things here anyway. I disagree because I feel the
performance has already degraded. There is a great reduction in
sensitivity because of something that I cannot hear (the notched carrier).
Why care about dynamic range in this case? Signals must be very strong
to even bring up a spurious on the noise level of the K3. Now I have
something I donot hear and dont want to hear that messes up the sensitivity.

There must be enough spare performance in the K3 to reduce ( I donot say
eliminate) the effect of the notched carrier?
Say up to the level of what the DSP filtering normally does if working
with a wide roofing filter.

I plee for a solution.

73
Arie PA3A

Op 10-11-2010 5:18, Johnny Siu schreef:
> I attempted to manual notch a strong carrier adjacent to a weak station.
> Although I was able to notch out the strong carrier (from the audio), there was
> no reduction in S meter level caused by that strong carrier. In other words,
> the weak station did not pop out from the noise because the stronger
> carrier de-sensed the K3 AGC.
>
> Johnny VR2XMC
>
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Johnny Siu

Manual notch In K3

Hello Arie,

Good, at least my observation is correct.

It is essential for a modern transceiver having the ability to notch a strong
unwanted carrier right at the front. Upon 'notch' of the offending carrier, the
'wanted' weak signal should prominently pop out from the noise. The effect of
the de-sensed AGC by the strong carrier should, by then, be greatly reduced.

I would consider 'AGC off' is a solution of the last resort. A high end radio
should not reply on this very last weapon.

73

Johnny VR2XMC

----- 郵件原件 ----
寄件人﹕ Arie Kleingeld PA3A <[hidden email]>
收件人﹕ [hidden email]
傳送日期﹕ 2010/11/10 (三) 9:26:35 PM
主題： Re: [Elecraft] Manual notch In K3

Johnny,

This is correct. Same experience here.

Although I would like that the notch would take the carrier out like a
conventional IF notch.

It has been said several times in the reflector that taking out the
carrier and increasing the gain again would degrade performance,
especially the dynamic range. If I do not reproduce this right, please
anyone in the group, please correct me.

What I think of this? I disagree strongly. Not on the IMD thing, I
cannot measure such things here anyway. I disagree because I feel the
performance has already degraded. There is a great reduction in
sensitivity because of something that I cannot hear (the notched carrier).
Why care about dynamic range in this case? Signals must be very strong
to even bring up a spurious on the noise level of the K3. Now I have
something I donot hear and dont want to hear that messes up the sensitivity.

There must be enough spare performance in the K3 to reduce ( I donot say
eliminate) the effect of the notched carrier?
Say up to the level of what the DSP filtering normally does if working
with a wide roofing filter.

I plee for a solution.

73
Arie PA3A

Op 10-11-2010 5:18, Johnny Siu schreef:
> I attempted to manual notch a strong carrier adjacent to a weak station.
> Although I was able to notch out the strong carrier (from the audio), there
was
> no reduction in S meter level caused by that strong carrier. In other words,
> the weak station did not pop out from the noise because the stronger
> carrier de-sensed the K3 AGC.
>
> Johnny VR2XMC
>
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Johnny Siu

Re： Manual notch In K3

In reply to this post by Johnny Siu

Thanks, James.

Yes, AGC off is the last weapon to use.

73 Johnny VR2XMC

----- 郵件原件 ----
寄件人﹕ JAMES ROGERS <[hidden email]>
收件人﹕ Johnny Siu <[hidden email]>
傳送日期﹕ 2010/11/10 (三) 9:09:09 PM
主題： Re: [Elecraft] Manual notch In K3

I wanted to check something before I answered this, but yes the notch filter is
probably in the audio chain, rather than the IF. I picked a good carrier on my
K3 and then applied the notch. the carrier was not diminished on the P3 display
but completely notched out in the audio from the speaker.

If I might suggest, in the situation you described apply the notch, reduce the
RF Gain, and turn the AGC off. This will remove the AGC action on the weak
signal. I often do this on weak DX as a matter of practice with or without the
notch. You can then advance the RF Gain to bring up the weak signal to a
comfortable level of copy.

73s Jim, W4ATK

On Nov 9, 2010, at 10:18 PM, Johnny Siu wrote:

> Hello Group,
>
> I attempted to manual notch a strong carrier adjacent to a weak station.
> Although I was able to notch out the strong carrier (from the audio), there
was

> no reduction in S meter level caused by that strong carrier. In other words,
> the weak station did not pop out from the noise because the stronger
> carrier de-sensed the K3 AGC.
>
> Please advise whether my observation is correct.
>
> TNX,
>
> Johnny VR2XMC
>
>
>
> ______________________________________________________________
> 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

JIM ROGERS
[hidden email]
http://web.me.com/jimrogers_w4atk

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Arie Kleingeld PA3A-2

Re: Manual notch In K3

In reply to this post by Johnny Siu

Johnny,

I agree with you. The K3 should be able to handle this.
As said, this issue has been addressed before.

But, it's all in the software and we'll have to see if something happens.

73,
Arie PA3A

Op 10-11-2010 14:39, Johnny Siu schreef:

> Hello Arie,
>
> Good, at least my observation is correct.
>
> It is essential for a modern transceiver having the ability to notch a strong
> unwanted carrier right at the front. Upon 'notch' of the offending carrier, the
> 'wanted' weak signal should prominently pop out from the noise. The effect of
> the de-sensed AGC by the strong carrier should, by then, be greatly reduced.
>
> I would consider 'AGC off' is a solution of the last resort. A high end radio
> should not reply on this very last weapon.
>
> 73
>
> Johnny VR2XMC
>

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Joe Subich, W4TV-4

Re: Manual notch In K3

Yes, manual notch should be moved inside the AGC loop
and let the HAGC activate if necessary to protect the
analog to digital converter.

73,

... Joe, W4TV

On 11/10/2010 10:02 AM, Arie Kleingeld PA3A wrote:

> Johnny,
>
> I agree with you. The K3 should be able to handle this.
> As said, this issue has been addressed before.
>
> But, it's all in the software and we'll have to see if something happens.
>
> 73,
> Arie PA3A
>
>
>
> Op 10-11-2010 14:39, Johnny Siu schreef:
>> Hello Arie,
>>
>> Good, at least my observation is correct.
>>
>> It is essential for a modern transceiver having the ability to notch a strong
>> unwanted carrier right at the front. Upon 'notch' of the offending carrier, the
>> 'wanted' weak signal should prominently pop out from the noise. The effect of
>> the de-sensed AGC by the strong carrier should, by then, be greatly reduced.
>>
>> I would consider 'AGC off' is a solution of the last resort. A high end radio
>> should not reply on this very last weapon.
>>
>> 73
>>
>> Johnny VR2XMC
>>
> ______________________________________________________________
> 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
>

ab2tc

Re: Manual notch In K3

In reply to this post by Arie Kleingeld PA3A-2

Hi,

Getting the manual notch inside the AGC loop is high on my wish list also.

AB2TC - Knut

Arie Kleingeld PA3A-2 wrote

Johnny,

I agree with you. The K3 should be able to handle this.
As said, this issue has been addressed before.

But, it's all in the software and we'll have to see if something happens.

73,
Arie PA3A

<snip>

Fabio Mantovani

Re: Manual notch In K3

I agree too!

Fabio
IZ4AFW / NZ1W

Il 10/11/2010 16.38, ab2tc ha scritto:

>
> Hi,
>
> Getting the manual notch inside the AGC loop is high on my wish list also.
>
> AB2TC - Knut
>
>
> Arie Kleingeld PA3A-2 wrote:
>>
>> Johnny,
>>
>> I agree with you. The K3 should be able to handle this.
>> As said, this issue has been addressed before.
>>
>> But, it's all in the software and we'll have to see if something happens.
>>
>> 73,
>> Arie PA3A
>>
>>
>> <snip>
>>
>

AC7AC

Re: Re： Manual notch In K3

In reply to this post by Johnny Siu

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