Re: Question about KNB2 Noise Blanker (Gain reductioninNB2 posit...

[VR2BrettGraham]

W3FPR replied to KH6AT that gated noise blankers cannot be expected
to work when the noise pulse is insufficient to reach the gating threshold
& that more signal might improve performance when blanking weak
noise.  Sounds reasonable, but...

I believe my other radios have gated noise blankers.  They behave far
better than the KNB2 in my K2 - even on noise that presumably is what
the KNB2 was designed for (chain saws, dirt bikes & similar stuff that
might be encountered by backpackers) - regardless of strength.

Outside of the type of noise the blanker is tailored for, why would it
be that a number of folks using one particular radio with a gated noise
blanker (K2 with KNB2) find the performance to be lacking compared to
other radios also with gated noise blankers?

73, VR2BrettGraham

_______________________________________________
Elecraft mailing list
Post to: [hidden email]
You must be a subscriber to post to the list.
Subscriber Info (Addr. Change, sub, unsub etc.):
 http://mailman.qth.net/mailman/listinfo/elecraft   

Help: http://mailman.qth.net/subscribers.htm
Elecraft web page: http://www.elecraft.com

[Don Wilhelm-3]

See comments below:
----- Original Message -----
From: "VR2BrettGraham" <[hidden email]>
To: <[hidden email]>
Sent: Saturday, January 01, 2005 9:37 AM
Subject: Re: [Elecraft] Question about KNB2 Noise Blanker
(GainreductioninNB2 posit...

> W3FPR replied to KH6AT that gated noise blankers cannot be expected
> to work when the noise pulse is insufficient to reach the gating threshold
> & that more signal might improve performance when blanking weak
> noise.  Sounds reasonable, but...
>
> I believe my other radios have gated noise blankers.  They behave far
> better than the KNB2 in my K2 - even on noise that presumably is what
> the KNB2 was designed for (chain saws, dirt bikes & similar stuff that
> might be encountered by backpackers) - regardless of strength.
>
> Outside of the type of noise the blanker is tailored for, why would it
> be that a number of folks using one particular radio with a gated noise
> blanker (K2 with KNB2) find the performance to be lacking compared to
> other radios also with gated noise blankers?
>

OTOH, many have reported that the K2 blanker is better.  I don't know the
real answer, but I can guess that the gain of a particular receiver ahead of
the noise blanker would make a big difference.  Multi-conversion receiver
designers have a lot more places to put the noise blanker (and more control
over the gain at that point) than is possible in a single conversion
receiver like the K2.  Try the K2 NB with the preamp set on to see if that
makes any difference, you may be surprised.

73,
Don W3FPR


_______________________________________________
Elecraft mailing list
Post to: [hidden email]
You must be a subscriber to post to the list.
Subscriber Info (Addr. Change, sub, unsub etc.):
 http://mailman.qth.net/mailman/listinfo/elecraft   

Help: http://mailman.qth.net/subscribers.htm
Elecraft web page: http://www.elecraft.com

[Larry - WA2DGD]

Hi

Just this week had an experience that confirms your findings.
Had a bad street lamp outside creating 30db over S9 noise across all bands.
The K2 was basically useless, with either combination of NB1 or NB2, Hi
or Lo threshold. Couldn't copy anything but noise.
Turned on my Kenwood TS940s and with either NB1 or NB2...no noise at
all, could easily copy signals that were too far under the noise for the K2.
The K2 NB  works great on the noise created when my xyl runs the
blender, then again so does the 940s.


> Outside of the type of noise the blanker is tailored for, why would it
> be that a number of folks using one particular radio with a gated noise
> blanker (K2 with KNB2) find the performance to be lacking compared to
> other radios also with gated noise blankers?
>
> 73, VR2BrettGraham


--
73
Larry
WA2DGD
K2 #1672
_______________________________________________
Elecraft mailing list
Post to: [hidden email]
You must be a subscriber to post to the list.
Subscriber Info (Addr. Change, sub, unsub etc.):
 http://mailman.qth.net/mailman/listinfo/elecraft   

Help: http://mailman.qth.net/subscribers.htm
Elecraft web page: http://www.elecraft.com

[VR2BrettGraham]

W3FPR added:

>>W3FPR replied to KH6AT that gated noise blankers cannot be expected
>>to work when the noise pulse is insufficient to reach the gating threshold
>>& that more signal might improve performance when blanking weak
>>noise.  Sounds reasonable, but...
>>
>>I believe my other radios have gated noise blankers.  They behave far
>>better than the KNB2 in my K2 - even on noise that presumably is what
>>the KNB2 was designed for (chain saws, dirt bikes & similar stuff that
>>might be encountered by backpackers) - regardless of strength.
>>
>>Outside of the type of noise the blanker is tailored for, why would it
>>be that a number of folks using one particular radio with a gated noise
>>blanker (K2 with KNB2) find the performance to be lacking compared to
>>other radios also with gated noise blankers?
>
>OTOH, many have reported that the K2 blanker is better.  I don't know the
>real answer, but I can guess that the gain of a particular receiver ahead
>of the noise blanker would make a big difference.  Multi-conversion
>receiver designers have a lot more places to put the noise blanker (and
>more control over the gain at that point) than is possible in a single
>conversion receiver like the K2.  Try the K2 NB with the preamp set on to
>see if that makes any difference, you may be surprised.

My impression is that whenever there is mention of the KNB2, there are
more posts about its ineffectiveness than anything else, as is the case
with this current thread.

I cannot recall any other rig using anything other than a gated noise
blanker, including those with single conversion receivers, such as the
TS-820.  I do not have an 820 here, but from my recollection of using one
with a vertical in an urban W7 environment, its noise blanker performed
better overall than the KNB2 in my K2/100.

Combinations of PREAMP & NB LEVEL settings on the K2 here tends
to have one of two results: no effect on noise, or totally trashing the
receiver.  My current QTH is in the middle of a mixed residential/industrial
area, with garages & work yards just next door doing plenty of arc welding
& other unsociable electromagnetic activities going on all around me - the
KNB2 is useless on most of it & even my lowly IC-706 does better.

I would suggest it is more a matter of the design of the KNB2 than the
fact that the K2 is a single conversion receiver.  I would agree with you
that variation in gain between K2s may be part of the problem, though
that really comes back to the design in the first place (consistency,
repeatability & ease of assembly & alignment being desirable in any
product, even a kit).

I also suspect that there are other factors that are involved or at least
aggravate things, as I find the KNB2 to be especially useless during
times that the AGC is responding to out of band energy (the EU 17m
problem recently noted in a post here by a bloke in NA - I experience
this on 15, 17, 20 & sometimes 30m).

But as the KNB2's performance continues to surface here from time
to time, there must be something behind it - we have enjoyed far
better performance from noise blankers in products with single, double
or however number of conversions in the receiver for decades.  I for
one hope that in any future products, Elecraft can improve upon this
& other attributes of their products that are lacking in comparison to
others on the market.

73, VR2BrettGraham

_______________________________________________
Elecraft mailing list
Post to: [hidden email]
You must be a subscriber to post to the list.
Subscriber Info (Addr. Change, sub, unsub etc.):
 http://mailman.qth.net/mailman/listinfo/elecraft   

Help: http://mailman.qth.net/subscribers.htm
Elecraft web page: http://www.elecraft.com

[Hisashi T Fujinaka]

On Sun, 2 Jan 2005, VR2BrettGraham wrote:

> My impression is that whenever there is mention of the KNB2, there are
> more posts about its ineffectiveness than anything else, as is the case
> with this current thread.

Er, I think people who don't have any trouble with it have no
inclination to respond. While I don't think it's the best noise blanker
I've ever used, my K2 is unusuable at my urban location without it.

On the noise here (power line noise and also some weird industrial
electrical noise) the noise blanker on the K2 works better than the
noise blanker on the IC-706MKIIG.

--
Hisashi T Fujinaka - [hidden email]
BSEE(6/86) + BSChem(3/95) + BAEnglish(8/95) + MSCS(8/03) + $2.50 = latte
_______________________________________________
Elecraft mailing list
Post to: [hidden email]
You must be a subscriber to post to the list.
Subscriber Info (Addr. Change, sub, unsub etc.):
 http://mailman.qth.net/mailman/listinfo/elecraft   

Help: http://mailman.qth.net/subscribers.htm
Elecraft web page: http://www.elecraft.com

[wayne burdick]

And now a word from the designer ;)

The KNB2 was designed largely around noise found at my QTH in Belmont.
I have pretty horrendous line noise at some times of the year, as well
as the usual collection of noisy light dimmers, etc. (My family was
amused by my running around, turning lamps up and down during the
process.) I also put the rig into various vehicles, including a very
noisy 1983 VW Vanagon. The blanker proved effective on all these
sources.

The KNB2 does have limitations. It sits at a wideband part of the RX
path, so in some cases it will be compromised by very strong in-band
signals. Fortunately this isn't a problem for most operators. It also
had to meet certain size and cost goals, limiting complexity; there
wasn't room for additional delay filtering, amplification, or more
serious gating hardware.

Beyond achieving an acceptable level of noise rejection, the KNB2 had
to satisfy one other criteria: to not degrade the dynamic range of the
receiver when it is turned on. It sits right at the post-amp output,
where a change in impedance could be problematic. So, one of the final
tasks was to come up with an RF band-pass filter for the blanker that
would present a decent SWR to the post-amp. The resulting filter has a
resistive divider rather than a capacitive divider (see the KNB2
schematic). This filter topology didn't have quite as long a delay as a
filter with a capacitive divider, but it made the post-amp happy and
still worked on all the noise sources I had available.

There are several approaches we could take to improve the KNB2's
performance. The one thing they have in common is adding a lot more
parts -- to the point that the entire module would have to be
surface-mount. For example, we could insert a narrowband diplexer at
its input. This would terminate the image at the post-amp, slightly
improve headroom of the RX strip, and reduce the swath of spectrum seen
by the blanker to about 50 kHz rather than the full width of the RF
bandpass filter.

I'm not sure when we'll be able to update the KNB2 design, but in the
meantime, I'll be happy to answer questions for anyone who wants to try
their hand at it. As must be obvious by now, we've worked hard to
integrate promising modifications in a timely fashion.

73,
Wayne
N6KR

---

http://www.elecraft.com

_______________________________________________
Elecraft mailing list
Post to: [hidden email]
You must be a subscriber to post to the list.
Subscriber Info (Addr. Change, sub, unsub etc.):
 http://mailman.qth.net/mailman/listinfo/elecraft   

Help: http://mailman.qth.net/subscribers.htm
Elecraft web page: http://www.elecraft.com

[VR2BrettGraham]

<[hidden email]> added:

>Er, I think people who don't have any trouble with it have no
>inclination to respond. While I don't think it's the best noise blanker
>I've ever used, my K2 is unusuable at my urban location without it.

True - as well as folks who are fortunate not to need to use the noise
blanker much, if not at all (my situation when I first started using my
K2).

>On the noise here (power line noise and also some weird industrial
>electrical noise) the noise blanker on the K2 works better than the
>noise blanker on the IC-706MKIIG.

I am frustrated this morning in not being able to measure the duration
of the noise pulses I have on 15 that the KNB2 will not touch but a
TS-950S' blanker does, which I suspect is from a power line as things
have been very cold & dry here (3-11C & 30-40% RH) recently.  As the
bands are not so good, I do not have constant S-meter indication from
out of band energy, so the noise amp should not be choked by the
AGC.  Is it not triggering, or is it that the noise gate is not triggered to
coincide with the pulses?  It is like it does nothing & this is the kind of
noise that from my experience is well within the capability of noise
blankers of other radios.

My KNB2 has blanked noise (so it probably is working normally), but is
very finicky about what it will work on.  It is likely I would not be able to
hear much of anything with my K2 from where I operate in 9M6, as last
time I was there there was S9 noise just like this everywhere.  This is
unfortunate, as there are other attributes of the K2 that are far superior
to my other equipment.

73, VR2BrettGraham

_______________________________________________
Elecraft mailing list
Post to: [hidden email]
You must be a subscriber to post to the list.
Subscriber Info (Addr. Change, sub, unsub etc.):
 http://mailman.qth.net/mailman/listinfo/elecraft   

Help: http://mailman.qth.net/subscribers.htm
Elecraft web page: http://www.elecraft.com

[Bob Nielsen]

On Sat, Jan 01, 2005 at 05:20:19PM -0800, Hisashi T Fujinaka wrote:

> On Sun, 2 Jan 2005, VR2BrettGraham wrote:
>
> >My impression is that whenever there is mention of the KNB2, there are
> >more posts about its ineffectiveness than anything else, as is the case
> >with this current thread.
>
> Er, I think people who don't have any trouble with it have no
> inclination to respond. While I don't think it's the best noise blanker
> I've ever used, my K2 is unusuable at my urban location without it.
>
> On the noise here (power line noise and also some weird industrial
> electrical noise) the noise blanker on the K2 works better than the
> noise blanker on the IC-706MKIIG.

Being in a semi-rural environment, I find that I don't have too many
times when the KNB2 is needed.  When the occasion does occur, it seems
to no less effective than the noise blanker on my TS-570D.  

Although it is designed for a different noise characteristic, I find
that the noise reduction of the KDSP2 is much more effective than that
of the TS-570D.

Bob Nielsen, N7XY
Bainbridge Island, WA




_______________________________________________
Elecraft mailing list
Post to: [hidden email]
You must be a subscriber to post to the list.
Subscriber Info (Addr. Change, sub, unsub etc.):
 http://mailman.qth.net/mailman/listinfo/elecraft   

Help: http://mailman.qth.net/subscribers.htm
Elecraft web page: http://www.elecraft.com

[wa4fom]

For what it's worth, with just one button press, my KNB2 will blank out
some pretty ugly pulse noise where I live that the blanker in my Ten-Tec
Orion only barely touches.  Not bad for one dinky little board, in my
opinion.

73 all,

Bob  WA4FOM
_______________________________________________
Elecraft mailing list
Post to: [hidden email]
You must be a subscriber to post to the list.
Subscriber Info (Addr. Change, sub, unsub etc.):
 http://mailman.qth.net/mailman/listinfo/elecraft   

Help: http://mailman.qth.net/subscribers.htm
Elecraft web page: http://www.elecraft.com

[Stewart Baker]

On Sat, 1 Jan 2005 17:51:33 -0800, wayne burdick wrote:
> And now a word from the designer ;)
------
> I'm not sure when we'll be able to update the KNB2 design, but in the
> meantime, I'll be happy to answer questions for anyone who wants to try
> their hand at it. As must be obvious by now, we've worked hard to
> integrate promising modifications in a timely fashion.
>
> 73,
> Wayne
> N6KR
>

>> A very comprehensive and interesting reply.
>> Many thanks Wayne.

>> 73
>> Stewart G3RXQ

_______________________________________________
Elecraft mailing list
Post to: [hidden email]
You must be a subscriber to post to the list.
Subscriber Info (Addr. Change, sub, unsub etc.):
 http://mailman.qth.net/mailman/listinfo/elecraft   

Help: http://mailman.qth.net/subscribers.htm
Elecraft web page: http://www.elecraft.com

[Tom Althoff]

That's been my experience here too.   Both the Orion and the KNB2 kill the
noise from my furnace as it zaps on but only the K2 was effective on the HF
noise generated by our microwave oven when it is on.

----- Original Message -----
From: <[hidden email]>
To: <[hidden email]>; <[hidden email]>
Sent: Sunday, January 02, 2005 1:12 AM
Subject: Re: [Elecraft] Question about KNB2 Noise Blanker

> For what it's worth, with just one button press, my KNB2 will blank out
> some pretty ugly pulse noise where I live that the blanker in my Ten-Tec
> Orion only barely touches.  Not bad for one dinky little board, in my
> opinion.
>
> 73 all,
>
> Bob  WA4FOM
> _______________________________________________
> Elecraft mailing list
> Post to: [hidden email]
> You must be a subscriber to post to the list.
> Subscriber Info (Addr. Change, sub, unsub etc.):
>  http://mailman.qth.net/mailman/listinfo/elecraft
>
> Help: http://mailman.qth.net/subscribers.htm
> Elecraft web page: http://www.elecraft.com

_______________________________________________
Elecraft mailing list
Post to: [hidden email]
You must be a subscriber to post to the list.
Subscriber Info (Addr. Change, sub, unsub etc.):
 http://mailman.qth.net/mailman/listinfo/elecraft   

Help: http://mailman.qth.net/subscribers.htm
Elecraft web page: http://www.elecraft.com

[Scott Prather]

It has been my experience that the KNB2 is one of the least effective noise
blankers that I've used on a current-production radio.  At night, I have a
high noise level produced by malfunctioning street lights (this has been
true for the 10 years I've lived here), and the KNB2 is completely
ineffective in blanking this noise while other radios such as my Ten-Tec
Paragon II or Drake TR-7 eliminate it completely. As a result, I cannot use
the K2 at night.

In an effort to understand why this is the case, I've looked at the received
noise with a spectrum analyzer.  I found that, while the noise sounds
continuous across the amateur band, it actually has large peaks and valleys,
in some cases varying up to 20 dB across the band.  Other noise sources,
such as electric motor noise (which the KNB2 blanks well, depending upon the
pulse repetition rate) are typically of nearly equal-amplitude across the
bandwidth of the RX front end.

About a year ago I spent a lot of time trying to improve the performance of
the KNB2, but my attempts were in vain, as any improvement in blanking
effectiveness caused a corresponding decrease in performance in some other
respect.  I finally gave up this effort, in my opinion the entire KNB2 needs
to be re-designed in order to meet the expectations of those of us who
really need it.

While I understand that there are folks on the reflector that claim the KNB2
does an excellent job of blanking this or that specific interference type,
in general I've found that such instances are relatively rare.  I have seen
the KNB2 work very well, there's no doubt in my mind that it can under the
proper conditions.  However, I agree with those on the reflector who see the
NB performance as a major impairment to an otherwise excellent receiver.  As
someone suggested, even if a portion of an updated NB had a surface-mount
aspect, that wouldn't be any different than what we had with the KDSP2, and
in my opinion, it's much more important.

Until a better design comes along for the NB, my K2 will continue to sit
unused in the evening when the blanker is needed.

Scott
N7NB




_______________________________________________
Elecraft mailing list
Post to: [hidden email]
You must be a subscriber to post to the list.
Subscriber Info (Addr. Change, sub, unsub etc.):
 http://mailman.qth.net/mailman/listinfo/elecraft   

Help: http://mailman.qth.net/subscribers.htm
Elecraft web page: http://www.elecraft.com

[Bill Steffey NY9H]

At 04:24 AM 1/2/2005, Stewart Baker wrote:

>On Sat, 1 Jan 2005 17:51:33 -0800, wayne burdick wrote:
> > And now a word from the designer ;)
>------
> > I'm not sure when we'll be able to update the KNB2 design, but in the
> > meantime, I'll be happy to answer questions for anyone who wants to try
> > their hand at it. As must be obvious by now, we've worked hard to
> > integrate promising modifications in a timely fashion.
> >
> > 73,
> > Wayne
> > N6KR
> >
>
> >> A very comprehensive and interesting reply.
> >> Many thanks Wayne.
>
> >> 73
> >> Stewart G3RXQ
>
>_______________________________________________
>Elecraft mailing list
>Post to: [hidden email]
>You must be a subscriber to post to the list.
>Subscriber Info (Addr. Change, sub, unsub etc.):
>  http://mailman.qth.net/mailman/listinfo/elecraft
>
>Help: http://mailman.qth.net/subscribers.htm
>Elecraft web page: http://www.elecraft.com

_______________________________________________
Elecraft mailing list
Post to: [hidden email]
You must be a subscriber to post to the list.
Subscriber Info (Addr. Change, sub, unsub etc.):
 http://mailman.qth.net/mailman/listinfo/elecraft   

Help: http://mailman.qth.net/subscribers.htm
Elecraft web page: http://www.elecraft.com

[Bill Steffey NY9H]

TNX WAYNE for the insights...

I look to seeing your "refinements" and other unique approaches to this noise
problem shared by many of us. Perhaps in the Kx ?

While either working or trying to work the VU4 ( only the log will tell)..
the old adage kept blinking at me " ya can't work em if ya can't hear em."

Commonwealth Edison was deliberately qrm'ing the VU4.

bill

_______________________________________________
Elecraft mailing list
Post to: [hidden email]
You must be a subscriber to post to the list.
Subscriber Info (Addr. Change, sub, unsub etc.):
 http://mailman.qth.net/mailman/listinfo/elecraft   

Help: http://mailman.qth.net/subscribers.htm
Elecraft web page: http://www.elecraft.com