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NB & Chirp

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n7ws

NB & Chirp

I worked and have since been listening to J79WE on 40m CW for some time. The wind is blowing about 40 mph so the power lines are acting up and I've been tweaking the noise blanker.

While playing around I noted that his signal had developed some chirp. I thought that strange, since he was clean when I worked him. I fired up old reliable, my TS870 and listened to him and he was T9 with no chirp (and no audio distortion). On the K3 he definitely had chirp, then I happened to turn off the noise blanker and the chirp went away.

The Noise blanker setting were IF=MED4 and DSP=T3-7. The chirp seems to be related to the DSP part of it.

Anyone else notice this?

Wes Stewart, N7WS

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Vic K2VCO

Re: NB & Chirp

Wes Stewart wrote:

> I worked and have since been listening to J79WE on 40m CW for some time. The wind is
> blowing about 40 mph so the power lines are acting up and I've been tweaking the noise
> blanker.
>
> While playing around I noted that his signal had developed some chirp. I thought that
> strange, since he was clean when I worked him. I fired up old reliable, my TS870 and
> listened to him and he was T9 with no chirp (and no audio distortion). On the K3 he
> definitely had chirp, then I happened to turn off the noise blanker and the chirp went
> away.
>
> The Noise blanker setting were IF=MED4 and DSP=T3-7. The chirp seems to be related to
> the DSP part of it.
>
> Anyone else notice this?

Are you sure it was chirp -- a change in frequency when keying? Or was it a softening of
the leading edge of the keyed elements?

The latter is characteristic of the DSP noise blanker when it's at an advanced setting,
like T3-7. Some distortion is part of the tradeoff for noise blanking.

I used to say "you know, it sounds like a guy with a slow-starting crystal oscillator"
until I realized that you very rarely hear any crystal-controlled rigs these days.
--
73,
Vic, K2VCO
Fresno CA
http://www.qsl.net/k2vco
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n7ws

Re: NB & Chirp

One of my first transmitters was a Millen with a keyed 6L6 crystal oscillator and an 807 final. So I know what chirp sounds like.

It sounded like chirp to me.

Wes

--- On Mon, 12/7/09, Vic K2VCO <[hidden email]> wrote:

> From: Vic K2VCO <[hidden email]>
> Subject: Re: [Elecraft] [k3] NB & Chirp
> To: "Wes Stewart" <[hidden email]>
> Cc: "Elecraft Reflector" <[hidden email]>
> Date: Monday, December 7, 2009, 11:26 PM
> Wes Stewart wrote:
> > I worked and have since been listening to J79WE on 40m
> CW for some time. The wind is
> > blowing about 40 mph so the power lines are acting up
> and I've been tweaking the noise
> > blanker.
> >
> > While playing around I noted that his signal had
> developed some chirp. I thought that
> > strange, since he was clean when I worked him. I
> fired up old reliable, my TS870 and
> > listened to him and he was T9 with no chirp (and no
> audio distortion). On the K3 he
> > definitely had chirp, then I happened to turn off the
> noise blanker and the chirp went
> > away.
> >
> > The Noise blanker setting were IF=MED4 and
> DSP=T3-7. The chirp seems to be related to
> > the DSP part of it.
> >
> > Anyone else notice this?
>
> Are you sure it was chirp -- a change in frequency when
> keying? Or was it a softening of the leading edge of the
> keyed elements?
>
> The latter is characteristic of the DSP noise blanker when
> it's at an advanced setting, like T3-7. Some distortion is
> part of the tradeoff for noise blanking.
>
> I used to say "you know, it sounds like a guy with a
> slow-starting crystal oscillator" until I realized that you
> very rarely hear any crystal-controlled rigs these days.
> -- 73,
> Vic, K2VCO
> Fresno CA
> http://www.qsl.net/k2vco
>

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Merv Schweigert

Re: NB & Chirp

In reply to this post by n7ws

Yes, I find on DSP settings on the NB over about 6 that there are some
type of artifacts that make the signal chirp or some sort of distortion.
Merv KH7C

> I worked and have since been listening to J79WE on 40m CW for some time. The wind is blowing about 40 mph so the power lines are acting up and I've been tweaking the noise blanker.
>
> While playing around I noted that his signal had developed some chirp. I thought that strange, since he was clean when I worked him. I fired up old reliable, my TS870 and listened to him and he was T9 with no chirp (and no audio distortion). On the K3 he definitely had chirp, then I happened to turn off the noise blanker and the chirp went away.
>
> The Noise blanker setting were IF=MED4 and DSP=T3-7. The chirp seems to be related to the DSP part of it.
>
> Anyone else notice this?
>
> Wes Stewart, N7WS
>
>
>
>
>
> ______________________________________________________________
> 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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>

n7ws

Re: NB & Chirp

Thanks Merv,

So it isn't my imagination as some have inferred.

Wes

--- On Tue, 12/8/09, Merv Schweigert <[hidden email]> wrote:

> From: Merv Schweigert <[hidden email]>
> Subject: Re: [Elecraft] [k3] NB & Chirp
> To: "Wes Stewart" <[hidden email]>
> Cc: "Elecraft Reflector" <[hidden email]>
> Date: Tuesday, December 8, 2009, 8:33 AM
> Yes, I find on DSP settings on the NB
> over about 6 that there are some
> type of artifacts that make the signal chirp or some
> sort of distortion.
> Merv KH7C
>
> > I worked and have since been listening to J79WE on 40m
> CW for some time. The wind is blowing about 40 mph so
> the power lines are acting up and I've been tweaking the
> noise blanker.
> >
> > While playing around I noted that his signal had
> developed some chirp. I thought that strange, since he
> was clean when I worked him. I fired up old reliable,
> my TS870 and listened to him and he was T9 with no chirp
> (and no audio distortion). On the K3 he definitely had
> chirp, then I happened to turn off the noise blanker and the
> chirp went away.
> >
> > The Noise blanker setting were IF=MED4 and
> DSP=T3-7. The chirp seems to be related to the DSP
> part of it.
> >
> > Anyone else notice this?
> >
> > Wes Stewart, N7WS
> >
> >
> >
> >
> >
> >
> ______________________________________________________________
> > 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
> >
> >
>
>

wayne burdick

Re: NB & Chirp [+ general discussion of DSP vs. IF noise blanking]

Administrator

Wes,

The DSP NB causes some artifacts at its higher settings. This is an
unavoidable side effect of signal processing.

The DSP NB is applied after the crystal filter, so the bandwidth is
already constrained, removing some of the inherent characteristics of
noise pulses, including their rise/fall time and shape. Thus it is
harder for the DSP to distinguish between signal and noise. On the
other hand, this is the only way to remove narrow-band noise (e.g.,
noise that appears every 10-15 kHz on a particular band, rather than
blanketing the entire band). The DSP NB also has the advantage of not
being "pumped" by distant signals outside the crystal filter.

The IF NB has the opposite situation to contend with. Noise pulse
shape and rise/fall time are preserved, so they can be effectively
gated. But if you set the threshold too low, the IF NB's noise gate
can be modulated by very strong adjacent signals.

By including both, we give the operator the ability to optimize the
ratio between IF and DSP blanking, which can be extremely effected as
attested to by many customers.

73,
Wayne
N6KR

Wes Stewart wrote:

> Thanks Merv,
>
> So it isn't my imagination as some have inferred.

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Dunc Carter - W5DC

Re: NB & Chirp

In reply to this post by n7ws

Assuming a simple blanking action that switches off the signal path
during the blanking pulse, you might be perceiving this as modulating
the input signal at the repetition signal of the blanking pulses. Let's
say that you have the signal tuned to the default center of the cw
passband at 600 Hz. If the blanking pulse has a repetition rate of
twice mains frequency where the mains frequency is 60 Hz, then you might
be hearing that as a 600 Hz signal modulated by 120 Hz pulses in
probably a complex manner which you might perceive as a chirp.
Practical use of a blanker is always a trade-off of noise reduction vs.
distortion. The K3 blanker is flexible and can even be used to reduce
and/or eliminate key clicks in some circumstances. I was able to
practice this during last weekend's 160 test where a local, K0RF, was
kind enough to provide a big signal with clicks throughout the contest;
the clicks could be reduced by up to 4 S-units on the K3 indicator with
the right blanker settings, improving the readability of nearby weak
signals.

73, Dunc, W5DC

Wes Stewart wrote:

> Thanks Merv,
>
> So it isn't my imagination as some have inferred.
>
> Wes
>
> --- On Tue, 12/8/09, Merv Schweigert <[hidden email]> wrote:
>
>
>> From: Merv Schweigert <[hidden email]>
>> Subject: Re: [Elecraft] [k3] NB & Chirp
>> To: "Wes Stewart" <[hidden email]>
>> Cc: "Elecraft Reflector" <[hidden email]>
>> Date: Tuesday, December 8, 2009, 8:33 AM
>> Yes, I find on DSP settings on the NB
>> over about 6 that there are some
>> type of artifacts that make the signal chirp or some
>> sort of distortion.
>> Merv KH7C
>>
>>
>>> I worked and have since been listening to J79WE on 40m
>>>
>> CW for some time. The wind is blowing about 40 mph so
>> the power lines are acting up and I've been tweaking the
>> noise blanker.
>>
>>> While playing around I noted that his signal had
>>>
>> developed some chirp. I thought that strange, since he
>> was clean when I worked him. I fired up old reliable,
>> my TS870 and listened to him and he was T9 with no chirp
>> (and no audio distortion). On the K3 he definitely had
>> chirp, then I happened to turn off the noise blanker and the
>> chirp went away.
>>
>>> The Noise blanker setting were IF=MED4 and
>>>
>> DSP=T3-7. The chirp seems to be related to the DSP
>> part of it.
>>
>>> Anyone else notice this?
>>>
>>> Wes Stewart, N7WS
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>> ______________________________________________________________
>>
>>> 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
>
>

Dunc Carter - W5DC

Re: NB & Chirp [+ general discussion of DSP vs. IF noise blanking]

In reply to this post by wayne burdick

Is the DSP blanker input level also subject to AGC?

Duncan, W5DC

Wayne Burdick wrote:

> Wes,
>
> The DSP NB causes some artifacts at its higher settings. This is an
> unavoidable side effect of signal processing.
>
> The DSP NB is applied after the crystal filter, so the bandwidth is
> already constrained, removing some of the inherent characteristics of
> noise pulses, including their rise/fall time and shape. Thus it is
> harder for the DSP to distinguish between signal and noise. On the
> other hand, this is the only way to remove narrow-band noise (e.g.,
> noise that appears every 10-15 kHz on a particular band, rather than
> blanketing the entire band). The DSP NB also has the advantage of not
> being "pumped" by distant signals outside the crystal filter.
>
> The IF NB has the opposite situation to contend with. Noise pulse
> shape and rise/fall time are preserved, so they can be effectively
> gated. But if you set the threshold too low, the IF NB's noise gate
> can be modulated by very strong adjacent signals.
>
> By including both, we give the operator the ability to optimize the
> ratio between IF and DSP blanking, which can be extremely effected as
> attested to by many customers.
>
> 73,
> Wayne
> N6KR
>
> Wes Stewart wrote:
>
>
>> Thanks Merv,
>>
>> So it isn't my imagination as some have inferred.
>>
>
>
> ______________________________________________________________
> 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
>
>

wayne burdick

Re: General discussion of DSP vs. IF noise blanking

Administrator

DSP noise blanking is applied after the hardware AGC, as in all other
rigs I know of that include DSP NB, but I believe it is pre-DSP-AGC.

Lyle may want to comment on this. I know we spent about a year
optimizing the gain balance!

73,
Wayne
N6KR

On Dec 8, 2009, at 9:39 AM, Duncan Carter wrote:

> Is the DSP blanker input level also subject to AGC?
>
> Duncan, W5DC

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Guy, K2AV

Re: NB & Chirp

In reply to this post by Dunc Carter - W5DC

Part of the back and forth on this thread seems to be over the
definition of "chirp".

The original definition of CW chirp, quite familiar in the 50's and
common, was a signal that went,

"Dwooooiiiieeeep Dwoooip Dwooooiiiieeeep Dwoooip

Dwooooiiiieeeep Dwooooiiiieeeep Dwoooip Dwooooiiiieeeep"

The signals of the time would sometimes traverse a kHz in a single
baud. With that reference in mind, the word "chirp" does not apply to
anything I have heard on my K3.

That is in contrast to a signal that would actually stay cleanly on
the same frequency, but whose amplitude would gradually rise during
the baud. This latter phenomenon, fairly rare by my recollection, was
never referred to as a chirp. I only ever heard that called soft
keying. The signal had to change frequency in the baud to be called a
chirp. There were signals that would gradually run up or down the
band as it was keyed. That wasn't called a chirp either.

I have never heard a DSP chirp on my K3 that wasn't a chirp coming in.
There certainly *IS* a *VERY* noticeable softening of leading and
trailing edges of CW bauds in some DSP NB settings, particularly 2-7
and 3-7. Frankly I find it annoying, just *FAR* less annoying than
the signal I want to listen to being buried in 20-30 dB of key clicks
:>) The artificial softening of the signal makes it "muddy", but as
I have found *NOT* less readable.

73, Guy.

It turns out there is a difference between "workable" and "pleasing"
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KK7P

Re: General discussion of DSP vs. IF noise blanking

In reply to this post by wayne burdick

>
> Is the DSP blanker input level also subject to AGC?
>

Hardware AGC - yes; software AGC - no.

73,

Lyle KK7P
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KK7P

Re: NB & Chirp [+ general discussion of DSP vs. IF noise blanking]

In reply to this post by wayne burdick

The DSP NB causes some artifacts at its higher settings.

Note that the DSP NB works by signal substitution while trying to
maintain frequency rather than just "blasting a hole" in the signal stream.

73,

Lyle KK7P
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Ken Alexander-2

XV50 Transverter (and more) for Sale

Several of my previously listed items have sold. The transverter and Heil Proset are still available at lower prices:

1. Elecraft XV50 6m transverter. Less than 1 yr old. Like-new condition and works very well. $325.00 (was $350.00)

2. Heil Proset with HC4 element. That's the DX/contesting element. Comes with adapter for Yaesu transceivers with RJ type mic connector. (I have replaced the original 1/4" headphone plug with a 1/8" plug) $80.00 (was $100.00)

Prices are in U.S. dollars. I will ship anywhere in Canada or continental U.S. at my expense.

Please contact me off-list.

Thank you & 73,

Ken Alexander
VE3HLS

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