Noise gen / Spectrogram--who invented?

[Steven Gibbs]

I recall using Rhode & Schwarz test-sets for filter
alignment, also Tektronix tracking-generator and
spectrum analyzer combos.  Further back I recall
similar devices called wobbulators used for IFs.

- when was the technique of using wideband noise
   followed by audio or video spectrum analysis first
   described?

- ditto, for amateur radio applications?

I know we must all thank N0SS for suggesting this
tecnique using the Spectrogram program for K2 filter
& BFO setting, and also for providing a circuit and
pcb for a suitable noise generator. -- A LOT better
than the other methods I mentioned above.

73, Steve GU3MBS.
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[Tom Hammond-3]

>I know we must all thank N0SS for suggesting this
>tecnique using the Spectrogram program for K2 filter
>& BFO setting, and also for providing a circuit and
>pcb for a suitable noise generator. -- A LOT better
>than the other methods I mentioned above.

I may have come up with using the noise generator as a signal source
(truthfully, I don't recall any more), but I was NOT the one to find and
suggest the use of Spectrogram... wish I had though... heheheh! In fact,
here are a couple opening paragraphs from my docs... trying to give credits
where it's really due...

   In September of 1999, Alan Childress, KM4DT, first brought our
   attention to the freeware program Spectrogram, and he first
   mentioned its use in aligning the K2's CW filters. Because it
   was such a radical concept, I think his comments tended to fall
   on deaf ears. Later, both W3GDZ and I wrote instructions for
   using Spectrogram
   (http://www.visualizationsoftware.com/gram.html1), to align the
   Elecraft K2's CW filters.

   Subsequent to both of those sets of instructions, Don Wilhelm,
   W3FPR, posted a fine description of the procedures he'd used to
   align his K2 for SSB reception, using Spectrogram. Again, it
   fell thru the cracks of the reflector and was lost. I doubt
   that many K2 owners picked up on it, and that's too bad.

   So, in response to several more recent requests, and in order
   to not have to re-write an individual paper for each future
   response to the subject, I am going to attempt to use Don's
   basic procedure and then set down some simple steps for basic
   alignment of the K2's SSB filters using Spectrogram. (I hope I
   can do justice to Don's initial efforts).

73,

Tom

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[Steven Gibbs]

Tom Hammond wrote:
> I was NOT the one to find and
> suggest the use of Spectrogram...

>   In September of 1999, Alan Childress, KM4DT, first brought our
>   attention to the freeware program Spectrogram, and he first
>   mentioned its use in aligning the K2's CW filters. Because it
>   was such a radical concept,

Yes, thanks Tom for setting out the facts, and our thanks to KM4DT.

Do Elecraft listers know of earlier mention of this technique in
the amateur or professional literature?

If not, then KM4DT deserves an even BIGGER accolade.  In any case,
many will acknowledge that making filter & BFO adjustent so
straightforward has contributed greatly to the K2's success.

73, Steve GU3MBS.




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[Jim Brown-10]

On Sun, 16 Jan 2005 14:27:51 +0000, Steven Gibbs wrote:

>I recall using Rhode & Schwarz test-sets for filter
>alignment, also Tektronix tracking-generator and
>spectrum analyzer combos.  Further back I recall
>similar devices called wobbulators used for IFs.
>
>- when was the technique of using wideband noise
>   followed by audio or video spectrum analysis first
>   described?
>
>- ditto, for amateur radio applications?

For roughly 35 years, pink noise and real time analyers have been used to
evaluate the amplitude response of audio systems and and equipment, adjust
system equaliztion for a desired response.

In the late 60's, the late Dick Heyser developed and patented a powerful
analysis technique the he called "Time Delay Spectrometry," whereby a
generator and narrowband detector were swept at the same rate, but with
time offset that could be set by the user. This allowed coherent
measurement of two-port systems -- that is, magnitude and phase -- and it
also allowed the direct sound of a loudspeaker to be separated from
reverberation in a room. Heyser demonstrated the technique to the pro audio
community using a collection of HP and GR gear that filled a van. It took
about ten years before Bruel and Kjaer built a dedicated product to do it.
Crown Int'l introduced a dedicated product in 1982. Although it wasn't
widely known, that box included FFT capability, and many of us, including
myself, used the FFT capability for various functions.

About that time, a number of folks began using single channel and dual
channel FFT analyzers to to analyze and tune sound systems. With the single
ended technique, the source was usually pink noise and you got only an
amplitude response. With dual channel analysis, one could compare any
excitation signal (including program material) with the output. These two
forms now dominate the landscape in pro audio. A program called Smaart, at
least some of which was written by a programmer who had been associated
with the Crown box, was introduced at least ten years ago. It runs on any
Windoze box, and uses the sound card for I/O. It is QUITE widely used to
tune live systems.

Nearly 25 years ago, I used my portable real time analyzer to determine the
response of systems where I had access to both input and output.  The
analyer could store and display two measurements, and I  subtracted them
point by point to get the system response. I did this with the telco links
between the Chicago FM Club's 146.76 repeater and two remote receivers in
the late-70's -- the input was my radio listening to a station on the
input, the output was the same radio listening to the repeater output. We
then adjusted an equalizer at the repeater site to optimize (or at least
improve) system response. I also used the technique professionally to
analyze the response of the duplication systems used for TV spots.

There are now dozens (hundreds?) of FFT programs written to run on PC's,
and for use in many disciplines. Spectrogram was written to facilitate the
analysis of bird calls! A very powerful new one called EASERA, for which I
have been a beta tester, was written  by some good friends in Berlin. It is
primarily a tool for acoustic testing, but from a single log sine sweep, it
can quickly computer and display harmonic distortion vs. frequency, BY
HARMONIC ORDER!

Jim Brown  K9YC


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[Gil Stacy]

Has anyone designed and made an Un-module for the KDSP2 or KAF2?  KE1L's
site does not list one.
http://w5big.home.comcast.net/K2_Un-modules.htm
I need to do some troubleshooting and want to avoid removing/replacing board
parts when I remove KDSP2 out of circuit.  Tnx.

73/Gil NN4CW
K2 #3104; KX1 #53


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[Geoffrey Mackenzie-Kennedy-2]

Good Evening Steve,

I cannot remember reading anything about the use of a noise generator for
"tuning" filters, but back in the early '50s we used to use a noise
generator plus spectrum analyser to align 30MHz IF strips used in radar
receivers. Also during the design of filters etc. We simply cranked up the
noise generator that was used for noise figure measurements, and the
technique was very useful also when designing antenna systems. But I have no
idea from whence the concept came.

But KM4DT and Tom ARE to be applauded for letting us know about Spectrogram
in this day of the PC, which as I see it gives us all a low (zero) cost LF
spectrum analyser. The mind boggles at the number of possible applications!

73,  Geoff   GM4ESD


----- Original Message -----
From: "Steven Gibbs" <[hidden email]>
To: <[hidden email]>
Sent: Sunday, January 16, 2005 4:35 PM
Subject: Re: [Elecraft] Noise gen / Spectrogram--who invented?

> Tom Hammond wrote:
> > I was NOT the one to find and
> > suggest the use of Spectrogram...
>
> >   In September of 1999, Alan Childress, KM4DT, first brought our
> >   attention to the freeware program Spectrogram, and he first
> >   mentioned its use in aligning the K2's CW filters. Because it
> >   was such a radical concept,
>
> Yes, thanks Tom for setting out the facts, and our thanks to KM4DT.
>
> Do Elecraft listers know of earlier mention of this technique in
> the amateur or professional literature?
>
> If not, then KM4DT deserves an even BIGGER accolade.  In any case,
> many will acknowledge that making filter & BFO adjustent so
> straightforward has contributed greatly to the K2's success.
>
> 73, Steve GU3MBS.
>

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[Ron D'Eau Claire-2]

Steve, GU3MBS:

I recall using Rhode & Schwarz test-sets for filter
alignment, also Tektronix tracking-generator and
spectrum analyzer combos.  Further back I recall
similar devices called wobbulators used for IFs.

- when was the technique of using wideband noise
   followed by audio or video spectrum analysis first
   described?

- ditto, for amateur radio applications?

-------------------------------

I can't cite the earliest documentation, but I know that filter-analysis
using broad-band noise and a spectrum analyzer combo was well known half a
century ago. In '62 I designed a production test station for Lenkurt
Electric using that process to align microwave filters.

The difference is that those set-ups covered a good-sized workbench and
would have cost us over $50,000 in today's money.  

The power of the PC coupled with some clever code that we can buy for almost
"pocket change" has made techniques that were barely affordable to a large
corporation back then almost a basic part of any Ham workshop today. The
biggest short-coming of Spectrogram is the PC, too. That's what limits the
usable dynamic range of the measurements to about 60 dB. It still takes
better gear to do real stop-band attenuation measurements.

The real advantage of Spectrogram is the visual display that is easily
interpreted.  It's "intuitive" by someone with a minimal understanding of
what's going on. That's exactly why we spent the money on the system I built
in the 60's. It needed to be operated correctly by factory alignment techs
with the least chance of error and  minimal 'training'. The same is true
today when someone wants to set up their K2 filters.

For more exacting measurements over a larger dynamic range, I still rely on
a combination of either a tunable signal generator and sensitive broad-band
RF voltmeter or a wide-band noise source and a tunable RF voltmeter. Indeed,
when I build a filter for a project that falls within the K2's tuning range,
the K2 itself makes a great tunable RF voltmeter for such a setup.

Ron AC7AC


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[Don Wilhelm-3]

Gil,

The 'un-module' consists only of 2 wires - pin 1 of J1 connects to pin 1 of
J2 and pin 2 of J1 connects to pin 2 of J2.
I just use 2 bent wires (component leads) between the 2 headers.  Of course,
a piece of PC board with pins in the correct places would be more
convenient - perhaps I will get aroung to building one someday, but for now
the 2 wire jumpers do the job.

73,
Don W3FPR

----- Original Message -----

>
> Has anyone designed and made an Un-module for the KDSP2 or KAF2?  KE1L's
> site does not list one.
> http://w5big.home.comcast.net/K2_Un-modules.htm
> I need to do some troubleshooting and want to avoid removing/replacing
> board parts when I remove KDSP2 out of circuit.  Tnx.
>
> 73/Gil NN4CW
> K2 #3104; KX1 #53


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[Stephen W. Kercel]

I was wondering if anyone on the reflector had tried building the
"Calibrated Noise Source" described starting on Page 25.27 of the 2005 ARRL
Handbook. If so, has anyone tried aligning a K2 with it?

The Handbook noise source looks like it would be more expensive and harder
to build than the Elecraft Ngen. Presumably the flat spectrum and precise
calibration of the Handbook generator make it better for doing noise figure
measurements.

Does anyone have some thoughts on the tradeoffs between the two generators?

73,

Steve Kercel
AA4AK


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[Don Wilhelm-3]

Steve,

A calibrated noise source is not necessary for aligning the K2 filters -
most any source of noise will do.  I have even heard that some folks were
successful with a bit of wire placed close to a lighted flourescent lamp.

If you have other needs for a calibrated noise source, you can also use it
for the K2 alignment, but that is much more than is needed for aligning the
K2 filters.

73,
Don W3FPR

----- Original Message -----

>I was wondering if anyone on the reflector had tried building the
>"Calibrated Noise Source" described starting on Page 25.27 of the 2005 ARRL
>Handbook. If so, has anyone tried aligning a K2 with it?
>
> The Handbook noise source looks like it would be more expensive and harder
> to build than the Elecraft Ngen. Presumably the flat spectrum and precise
> calibration of the Handbook generator make it better for doing noise
> figure measurements.
>
> Does anyone have some thoughts on the tradeoffs between the two
> generators?
>
> 73,
>
> Steve Kercel
> AA4AK
>
>
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[Stephen W. Kercel]

Don:

Thanks,

Steve


At 08:23 PM 1/16/2005 -0500, you wrote:

>Steve,
>
>A calibrated noise source is not necessary for aligning the K2 filters -
>most any source of noise will do.  I have even heard that some folks were
>successful with a bit of wire placed close to a lighted flourescent lamp.
>
>If you have other needs for a calibrated noise source, you can also use it
>for the K2 alignment, but that is much more than is needed for aligning
>the K2 filters.
>
>73,
>Don W3FPR
>
>----- Original Message -----
>>I was wondering if anyone on the reflector had tried building the
>>"Calibrated Noise Source" described starting on Page 25.27 of the 2005
>>ARRL Handbook. If so, has anyone tried aligning a K2 with it?
>>
>>The Handbook noise source looks like it would be more expensive and
>>harder to build than the Elecraft Ngen. Presumably the flat spectrum and
>>precise calibration of the Handbook generator make it better for doing
>>noise figure measurements.
>>
>>Does anyone have some thoughts on the tradeoffs between the two generators?
>>
>>73,
>>
>>Steve Kercel
>>AA4AK
>>
>>
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>
>

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[Ron D'Eau Claire-2]

Don wrote:
A calibrated noise source is not necessary for aligning the K2 filters -
most any source of noise will do.  I have even heard that some folks were
successful with a bit of wire placed close to a lighted flourescent lamp.

---------------------

Ordinary background QRN on 80 or 160 meters works FB too. Just avoid any
frequency where a signal falls within the bandpass. If the background QRN is
not loud enough for someone on 80 or 160 (lucky, lucky you having THAT QTH!)
just turn on the Preamp.

I use a noise source only when I'm in the shop away from an antenna. There's
absolutely NOTHING about a noise generator in this application that makes
the alignment any more "perfect". The noise source is just a convenience. At
times when an antenna is not available it's a convenience well worth having,
but that's all it is.

Ron AC7AC


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[Stephen W. Kercel]

Ron:

Your points are well taken.

Clearly a calibrated noise generator is overkill.

The problem with a 160/80m antenna is that one is not always conveniently
accessible.

If a person did not wish to fork over the $40 or so for the Elecraft noise
generator, it occurs to me that there is one other possibility. Lots of
hams (including me) have a noise bridge (such as the MFJ-202), and it might
be a good noise source for alignment. The load port could be terminated in
either a short, an open, a 50 ohm fixed load, or practically anything else.
All that would be necessary is being sure that the tunable impedances in
the bridge are set such that they are well away from the impedance of the load.

Does this approach present a pitfall that has not yet occurred to me?

73,

Steve
AA4AK

>Ordinary background QRN on 80 or 160 meters works FB too. Just avoid any
>frequency where a signal falls within the bandpass. If the background QRN is
>not loud enough for someone on 80 or 160 (lucky, lucky you having THAT QTH!)
>just turn on the Preamp.
>
>I use a noise source only when I'm in the shop away from an antenna. There's
>absolutely NOTHING about a noise generator in this application that makes
>the alignment any more "perfect". The noise source is just a convenience. At
>times when an antenna is not available it's a convenience well worth having,
>but that's all it is.
>
>Ron AC7AC
>
>
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[Ron D'Eau Claire-2]

Since the Tsunami in the Indian Ocean, my KX1 has become the centerpiece of
discussions with non-hams here in Forest Grove (we're about 17,000 people in
a typical western town dating back to the late 1800's, about 30 miles west
of Portland).

We live in a region threatened by tsunami's, earthquakes and volcanic
eruptions (Although were over 100 miles away, Mt. St. Helens dumped so much
ash on parts of the town that it took weeks to dig out. Some residents made
concrete out of it for their retaining walls and walkways - it's still as
fresh and strong as the day it was poured!) Some of the world's greatest
forest fires have occurred right here in our beautiful Tillamook Forest.

Unlike the Indian Ocean, we have an extensive tsunami alert and evacuation
system all along the Oregon coast, extending south into northern California
and north through Washington state. Earthquakes here aren't the frequent
little rockers California expects, but very infrequent (thankfully) quakes
in the Richter 8 or 9 range that leave little of anything standing for many,
many of miles in all directions. They are typical of "subduction" zones like
here, and like Sri Lanka.

So the "wake up call" on Dec 26 got some people to talking and wondering
about what they'd do. Everyone knows the phone system and power grid are the
first causalities in any serious disaster. I took the opportunity to make my
KX1 the center piece of some discussions with non-hams in Forest Grove.

About my KX1 I explained, "This little box that fits in my jacket pocket is
a complete short-wave radio station that I built. I can throw a wire over a
tree limb and contact other people over a range of hundreds of miles,
thousands of miles, even half way around the world at times. It requires no
satellites, no cellular towers and no telephone or power lines. It requires
nothing at all but me and the other station. It even contains its own
batteries, and when they die I can hook onto any car battery and it will
operate for weeks, at least.

I am a Amateur Radio Operator, a "Ham", licensed by the federal government
to build, maintain and operate this equipment. There are hundreds of
thousands of us all over the USA. Many of us are organized into emergency
networks that meet on the air whenever a disaster strikes. We are here to
serve you in the event of an earthquake, tsunami or other disaster just as
Amateur Radio Operators have provided essential communications in Sri Lanka.
It's what Hams do when things go wrong."

To my surprise and pleasure, several people, non Hams, have shared their own
stories about how Hams have helped them or family members in the past, and
how grateful they are that there are Hams active in our town.  

These are great public relations tools, these Elecraft rigs. Don't let any
opportunity pass to tell non-Hams who you are and  emphasize what you can do
when all else goes wrong.

Of course, we must be prepared for the day we are needed.

It may be the most important thing we do.

Ron AC7AC


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[Ron D'Eau Claire-2]

No pitfall that I can see, Steve.  The noise bridge should be FB!  All you
want is a noise source that is constant in level over the range of a few kHz
that is strong enough to see on your display.

The kits are a great convenience. Convenience always cost a little extra
<G>. One time when I got frustrated by not having a an antenna at my
workbench that picked up enough noise, I built a noise generator completely
out of my junk box. I think all the parts new would be under US$10 new. Tom,
N0SS, published the layout on his website. It's at http://tinyurl.com/4qggr

I used a little plastic box I had picked up at "Tap Plastics" - a retail
plastic goody outlet that is all over the country, I think. The key is short
leads. It's strong enough that I have to replace the box. I dropped it down
the stairs onto the concrete shop floor and broke the case, but some tape
keeps it working FB <G>. Such point-to-point construction is really very,
very strong.

And it puts out very useful noise levels for peaking circuits from a few
hundred kHz up through 440 MHz.

Ron AC7AC



-----Original Message-----
Ron:

Your points are well taken.

Clearly a calibrated noise generator is overkill.

The problem with a 160/80m antenna is that one is not always conveniently
accessible.

If a person did not wish to fork over the $40 or so for the Elecraft noise
generator, it occurs to me that there is one other possibility. Lots of
hams (including me) have a noise bridge (such as the MFJ-202), and it might
be a good noise source for alignment. The load port could be terminated in
either a short, an open, a 50 ohm fixed load, or practically anything else.
All that would be necessary is being sure that the tunable impedances in
the bridge are set such that they are well away from the impedance of the
load.

Does this approach present a pitfall that has not yet occurred to me?

73,

Steve
AA4AK

>Ordinary background QRN on 80 or 160 meters works FB too. Just avoid
>any frequency where a signal falls within the bandpass. If the
>background QRN is not loud enough for someone on 80 or 160 (lucky,
>lucky you having THAT QTH!) just turn on the Preamp.
>
>I use a noise source only when I'm in the shop away from an antenna.
>There's absolutely NOTHING about a noise generator in this application
>that makes the alignment any more "perfect". The noise source is just a
>convenience. At times when an antenna is not available it's a
>convenience well worth having, but that's all it is.
>
>Ron AC7AC
>
>
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[Ron D'Eau Claire-2]

I got a report that the url for the noise generator I posted before wasn't
working.

Sorry about that. It seem like the "tinyurl" web site is not working
properly. Here's the direct link to the file on Tom, N0SS, website:
http://www.n0ss.net/noise_generator_ac7ac-style.pdf

Ron AC7AC


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[Mike Morrow-3]

Ron wrote:

>About my KX1 I explained, "This little box that fits in my jacket
>pocket is a complete short-wave radio station that I built. I can
>throw a wire over a tree limb and contact other people over a
>range of hundreds of miles, thousands of miles, even half way
>around the world at times. It requires no satellites, no cellular
>towers and no telephone or power lines. It requires nothing at
>all but me and the other station.

Hi Ron,

That describes exactly the kick I get from operating out in the boonies on HF.  No infrastructure is required, just the radios on each end and the physics of wave propagation between them.

I enjoy reading my old 1930s QSTs where there are occassionally stories of amateur radio support in flooding, tornado, and other emergencies, using vacuum tube gear that was difficult to power, and Morse as the mode.  Today, I do have doubts about the practical value of amateur radio emergency communications in all but extremely rare situations.  The cellular phone systems in many places in the world are surprisingly robust and reliable.  I know I was able to keep in touch with my brother in Pensacola a few months ago with him using a cell phone all through and after hurricane Ivan, and I know others who did the same for other hurricanes last Summer.  All had lost power and landlines for days or weeks, yet their cell phones worked as long as they had charged battery packs.  Apparently the same thing has occured in Asia, except where there had been no cell coverage.  Impressive.

There were, I'm sure, isolated regions where ham radio provided help, and I suspect that in the USA those rural and wilderness area where cell coverage is still spotty (my favorite spot in the Arkansas Ozarks has no cell coverage except on high ridges, for example), HF ham ops still have some small potential for emergencies, especially if VHF repeaters are off air.

I somehow doubt the practical value of HF QRP and/or Morse operations in providing today significant emergency communications capability under most likely encountered conditions.  I believe that the design of any serious HF emergency communications system should include a 100 watt output rig capable of SSB operation in the 40m and 80m bands, with large deep discharge batteries for power and some sort of gasoline-powered charging system (no solar arrays), and a real antenna (No buddi-poles, miracle whips, MP-1s, etc.).  If I were organizing ham radio support on HF, the last thing I'd want is everyone showing up with 5 watt 20m CW rigs powered from AA cells.  But anything would be better than nothing in a last resort!

73,
Mike / KK5F


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[Tony Wells]

I noticed in this month's RADCOM that there was a letter complaining about
the Technical Topics (TT) Column containing too much historical stuff about
valve-based rigs. In the previous month's TT there was a comment by Pat
himself that the modern day rigs were too much "black boxes" and it was
difficult for hams to understand what is going on inside these things.

Well it occurred to me that as the Elecraft info is so "open source" this
would be a great opportunity for someone, or several people here to put
forward some pieces for TT at the block-diagram level about how the K1 and
K2 are put together and why the K2 gets its great rig comparison figures .
This month's TT covers ergonomic issues of old vs. new rgs, and this would
be another opportunity to explain the history and evolution behind the K2
button setup.

Much of the hard work is already available in the form of diagrams etc.

Anyone interested - and not necessarily G-land hams?

Regards

Tony
G7IGG

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[Brian Mury-3]

On Mon, 2005-17-01 at 10:33 -0600, Mike Morrow wrote:
> Today, I do have doubts about the practical value of amateur radio
> emergency communications in all but extremely rare situations.  The
> cellular phone systems in many places in the world are surprisingly
> robust and reliable.

Both our landline and cellular networks went down a few years ago after
an earthquake that did not even cause any damage - just from overload.
What would happen after an earthquake that caused severe damage, injury,
and loss of life?

> I somehow doubt the practical value of HF QRP and/or Morse operations
> in providing today significant emergency communications capability
> under most likely encountered conditions.

I don't know if it was QRP, but HF CW was used after the tsunami.

--
73, Brian
VE7NGR

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