Old noise generator
Tim Williams
it, though I did see an ad in an old journal proclaiming it's good to four
sigmas. It seems to be roughly "audio frequency", by which I mean, the
circuits are audio quality, no particular attention paid to high or low
frequency bandwidth (AC coupled, no peaking coils). I would guess 10Hz to
200kHz or so.
Front view. Some old rackmount thing:
http://myweb.msoe.edu/williamstm/Images/Gaussian_Noise1.jpg
So I'm guessing Beloit got it from NASA surplus or something. I found this
thing on the curb one day outside of a house near the college, which I'm
assuming is the residence of someone interested in Beloit physics...
Other side of the faceplate:
http://myweb.msoe.edu/williamstm/Images/Gaussian_Noise2.jpg
Behind the faceplate, the noise generator and amplifiers:
http://myweb.msoe.edu/williamstm/Images/Gaussian_Noise3.jpg
On the far right, two 6D4 gas thyratron triodes are set in magnetic fields,
generating noise per the datasheet. They look to be connected like any old
gas tube, with coupling capacitors going to the rest of the circuit. I'm
going to guess they use two and mix them somewhere (I haven't traced the
circuit yet), to make it extra randomized or something.
Signal leaves through the coax in the top-right corner, which goes to the
output stage on the left (coupled through that big fat 1.0uF). I think it's
a 12AU6 cathode follower.
On the far left, two PCBs hold some germanium transistors (typical date
codes are 1963), the TO-39's are 2N398As, while the TO-1's are something
rather fancy (I forget the number, but they're epitaxial mesa germaniums
with almost 100MHz fT). I don't really know what to make of it, but it must
be in the signal path, why else use such fast transistors.
PCB closeups:
http://myweb.msoe.edu/williamstm/Images/Gaussian_Noise4.jpg
Gotta love that clear glass body RN60B!
The power supply hangs in the back of the rackmount chassis (which must be
annoying for the moment arm...)
http://myweb.msoe.edu/williamstm/Images/Gaussian_Noise5.jpg
Two potted transformers supply everything, I think one is for heaters, the
other for HV, and the thermal relay (bottom right) delays HV by a minute or
whatever. Rectifiers are all silicon (I guess).
A 6BX7 and associated tubes (12AX7, and the other one may be another 12AX7)
regulate high voltage. The two PCBs and heatsink appear to regulate 12.6V
for heaters. The TO-3's are all 30V, 1-5A germaniums. The two pots say
they're for + and - 156V, I guess one or both go to the tube regulator part.
Either that or some of the TO-39's are HV germaniums, I haven't checked.
Rear view:
http://myweb.msoe.edu/williamstm/Images/Gaussian_Noise6.jpg
Filament supply seems to be the bottom transformer, feeding a press-mounted
FWB and computer-grade cap.
Tim
--
Deep Friar: a very philosophical monk.
Website: http://webpages.charter.net/dawill/tmoranwms
John Larkin
Yikes, that must have cost a fortune, back when.
The gas tubes tended to make asymmetric (not prefectly Gaussian)
noise, so people subtracted the output of two tubes. Nowadays,
pseudo-random is easier.
Hey, we have clouds too.
John
Tim Williams
news:eustg51jq54o7lgk3...@4ax.com...
> Yikes, that must have cost a fortune, back when.
>
> The gas tubes tended to make asymmetric (not prefectly Gaussian)
> noise, so people subtracted the output of two tubes. Nowadays,
> pseudo-random is easier.
Ahh. Say, that reminds me: I once ran a zener at fairly low current, and
saw a jagged waveform, as if the junction (which is avalanching, since this
was like 12V or so) has a randomly variable threshold and hysteresis band.
Say, gas discharges are avalanche, too -- same physical phenomenon? I can
see subtraction having some use there.
> Hey, we have clouds too.
Ah, snooping around my directory? Well, since I'm on a higher floor at
school than I've even lived on before (which still isn't much, this is
Wisconsin after all), I can get a good eye on the weather. Last month there
was a span of two solid weeks of that sort of inland moisture coming up off
the lake. Bleh. But you'd be no stranger to that in SF, I've seen your fog
before.
http://myweb.msoe.edu/williamstm/Images/Cloudy.jpg
Most of the time, it's average midwestern weather. West coast of the lake
doesn't get much lake effect.
http://myweb.msoe.edu/williamstm/Images/Panorama2sm.jpg
The animated GIF,
http://myweb.msoe.edu/williamstm/Images/Clouds.gif
I took each frame about 15 seconds apart. Really weird, I've never seen a
ribbon of cloud moving out to 'sea' before. Fairly straight edge, a few
thousand feet long, and moving at a pretty good clip. The edge was, ohh I'd
guess a hundred feet tall, and rolling back fairly well (in most frames, you
can see the edge curling over).
http://myweb.msoe.edu/williamstm/Images/Rainbow1.jpg
Milwaukee's three tits,
http://myweb.msoe.edu/williamstm/Images/Milwaukee_Domes.jpg
Tallest building in Wisconsin:
http://myweb.msoe.edu/williamstm/Images/US_Bank.jpg
http://myweb.msoe.edu/williamstm/Images/Moon.jpg
I took these around Beloit College,
http://myweb.msoe.edu/williamstm/Images/SkyFire.jpg
http://myweb.msoe.edu/williamstm/Images/MorningRain.jpg
The joys of winter,
http://myweb.msoe.edu/williamstm/Images/Icy1_lg.JPG
http://myweb.msoe.edu/williamstm/Images/Icy3.jpg
John Larkin
<tmor...@charter.net> wrote:
>"John Larkin" <jjSNIP...@highTHISlandtechnology.com> wrote in message
>news:eustg51jq54o7lgk3...@4ax.com...
>> Yikes, that must have cost a fortune, back when.
>>
>> The gas tubes tended to make asymmetric (not prefectly Gaussian)
>> noise, so people subtracted the output of two tubes. Nowadays,
>> pseudo-random is easier.
>
>Ahh. Say, that reminds me: I once ran a zener at fairly low current, and
>saw a jagged waveform, as if the junction (which is avalanching, since this
>was like 12V or so) has a randomly variable threshold and hysteresis band.
>Say, gas discharges are avalanche, too -- same physical phenomenon? I can
>see subtraction having some use there.
Yup, a regular zener like a 1N758 will make pretty good gausian noise
at several mA bias, ballpark 300 nV/rootHz. As the current drops, the
noise starts to get asymmetric and at low currents turns into a very
noisy sawtooth. Subtracting two diode signals would be good here, too,
if extreme noise quality were needed.
>
>> Hey, we have clouds too.
>
>Ah, snooping around my directory? Well, since I'm on a higher floor at
>school than I've even lived on before (which still isn't much, this is
>Wisconsin after all), I can get a good eye on the weather. Last month there
>was a span of two solid weeks of that sort of inland moisture coming up off
>the lake. Bleh. But you'd be no stranger to that in SF, I've seen your fog
>before.
>http://myweb.msoe.edu/williamstm/Images/Cloudy.jpg
Our house overlooks the Alemany Gap, a break in the coast range hills
between the ocean and the bay. It's a major fog duct. Some days the
fog settles into the gap and it looks like a river with houses on the
shore. Some days we can't see the next street. We leave the heat on
all year.
>
>Most of the time, it's average midwestern weather. West coast of the lake
>doesn't get much lake effect.
>http://myweb.msoe.edu/williamstm/Images/Panorama2sm.jpg
I spent some time in Madison, mostly summer, and it was nice, drinking
beer in the student union on the lake. Lots of good coffeehouses and
restaurants and such. Great Farmers' Market outside the capital
building on Saturdays.
I helped this thing
get started, a spinout of the ME department at UW.
Hmmm, it's almost time for pecan pie.
John
Tim Williams
> I spent some time in Madison, mostly summer, and it was nice, drinking
> beer in the student union on the lake. Lots of good coffeehouses and
> restaurants and such. Great Farmers' Market outside the capital
> building on Saturdays.
Yep, lots of good food, good beer and most of all, great cheese. ;-)
> I helped this thing
>
> http://www.imago.com/imago/
>
> get started, a spinout of the ME department at UW.
Interesting. So, they put a big stinking pulse into it, which rips off and
ionizes exactly the surface atoms, which are then detected in time and
space, I suppose with microchannel plates?
> Hmmm, it's almost time for pecan pie.
Ahh, we didn't have any. But we did have pumpkin chocolate chip cheesecake,
which is also quite delectable.
John Larkin
<tmor...@charter.net> wrote:
>"John Larkin" <jjSNIP...@highTHISlandtechnology.com> wrote in message
>news:mcfug5h8vf2vftmoa...@4ax.com...
>> I spent some time in Madison, mostly summer, and it was nice, drinking
>> beer in the student union on the lake. Lots of good coffeehouses and
>> restaurants and such. Great Farmers' Market outside the capital
>> building on Saturdays.
>
>Yep, lots of good food, good beer and most of all, great cheese. ;-)
>
>> I helped this thing
>>
>> http://www.imago.com/imago/
>>
>> get started, a spinout of the ME department at UW.
>
>Interesting. So, they put a big stinking pulse into it, which rips off and
>ionizes exactly the surface atoms, which are then detected in time and
>space, I suppose with microchannel plates?
Yup. The idea is to rip off, statistically, maybe one ion every 5 or
10 pulses to avoid pileup confusion. The ion flies radially away from
the nominally spherical tip, 100 nm diameter maybe, and it hits a
microchannel plate. The field strengths are insane. The magnification
is millions. The MCP makes a burst of electrons out the other side,
and that hits a 2-axis delay-line detector. If we measure the four
pulses that emerge from the two crossed serpentine delay lines, we can
figure out the X-Y hit location and the time of flight (ie, the mass =
elemental composition and isotope of that ion.) So as the tip is
eroded away, we can reconstruct a 3D image of the atoms. The tip is
cooled to 40K or some such to keep the atoms from wandering around.
Ultra-high vacuum, too. It all gets expensive.
http://www.google.com/patents/about?id=MNd3AAAAEBAJ&dq=7019307
For some materials, it's better to whack the sample with a femtosecond
laser rather than a high-voltage pulse, to eject the ion. Did I
mention expensive?
>
>> Hmmm, it's almost time for pecan pie.
>
>Ahh, we didn't have any. But we did have pumpkin chocolate chip cheesecake,
>which is also quite delectable.
Kids these days!
John
Paul Hovnanian P.E.
>
> This is an Elgenco 331A gaussian noise generator.
Sorry. I thought this was a thread about our resident right wing nuts.
Never mind.
--
Paul Hovnanian mailto:Pa...@Hovnanian.com
------------------------------------------------------------------
Nondeterminism means never having to say you are wrong.
Tim Williams
news:4B108274...@hovnanian.com...
> Sorry. I thought this was a thread about our resident right wing nuts.
>
> Never mind.
Ah, good point. They're a little slow for this application, but you might
tempt some cryptologists into downloading their entropy. Run the archives
through a hash function and you've got a lovely source of random numbers.
Joop
>at several mA bias, ballpark 300 nV/rootHz. As the current drops, the
>noise starts to get asymmetric and at low currents turns into a very
>noisy sawtooth. Subtracting two diode signals would be good here, too,
>if extreme noise quality were needed.
>
One example I found on the net suggest 24V zeners with a current
source of about 20mA. However I have plenty of 9.1V/500mW smd ones in
the cupboard that I could use in series.
Joop
Tim Williams
news:d4l3h5l2imd8hm377...@4ax.com...
> Would adding do something similar?
> One example I found on the net suggest 24V zeners with a current
> source of about 20mA. However I have plenty of 9.1V/500mW smd ones in
> the cupboard that I could use in series.
They're fine at a few mA. 9.1V might be a little low; I forget how the
noise of zener effect compares to avalanche. Generally, the zener effect
ends around 6V (the crossover point having an interestingly low tempco right
around 6.2-6.8V), so >6V zeners are actually avalanche diodes.
John Larkin
The Central Limit Theorem says that summing a number of imperfect
noise sources trends towards Gaussian. I don't know if putting zeners
in series is equivalent to summing noise sources, or if three 9 volt
zeners in series behave like a single 27. I doubt it.
Just because something is on the net doesn't make it sensible. 9.1
volt zeners, biased to maybe 5 mA, make nice noise. Sum a few or
better yet sum and difference an even number of them... that's
probably a faster approach to good gaussian noise than straight
summing.
Summing does push the probability distribution towards gaussian, but
it doesn't much improve spectral flatness.
John
Joop
I think it was only mentioned that the 24V zener produced more noise
power than a 9V one. On flatness the different voltages were not
compared. The current had some influence on flatness though.
I guess I will just experiment and see what it brings.
Thanks for responding.
Joop
John Larkin
Gain is cheap. The noise from an opamp or a mmic will tend to be of
lower quality than the noise from a zener, so all you need is enough
zener noise to swamp the noise of whatever amplifier you'll use after
the zener. A 9.1 volt zener will make several hundred nv/rthz, plenty
to blast past the noise of a good opamp or mmic, which would be a few
nv/rthz.
If you do get any data on zener noise for various diodes at different
currents, please post it.
John
RST Engineering
<jjla...@highNOTlandTHIStechnologyPART.com> wrote:
.
>
>Just because something is on the net doesn't make it sensible. 9.1
>volt zeners, biased to maybe 5 mA, make nice noise.
How high in frequency does the noise extend with reasonable flatness,
John?
Jim
Tim Williams
news:lk95h5pc5f9cjme28...@4ax.com...
>>Just because something is on the net doesn't make it sensible. 9.1
>>volt zeners, biased to maybe 5 mA, make nice noise.
>
> How high in frequency does the noise extend with reasonable flatness,
> John?
Offhand, I once hooked up a 1N4742 at around 5mA and 'counted' the
frequency. It was somewhere in the 160-240kHz range, so I guess bandwidth
won't be far past there. Zeners have pretty fat junctions, so you can't
expect much. Low wattage zeners might have some RF performance.
John Larkin
Don't know. It's clearly limited by the corner formed by the junction
capacitance and the zener dynamic impedance.
Here's some good stuff:
http://www.noisecom.com/product_NC100-400Series.asp
They have diodes rated from 100 KHz to 100 GHz.
John
RST Engineering
<jjla...@highNOTlandTHIStechnologyPART.com> wrote:
>Don't know. It's clearly limited by the corner formed by the junction
>capacitance and the zener dynamic impedance.
>
>Here's some good stuff:
>
>http://www.noisecom.com/product_NC100-400Series.asp
>
>They have diodes rated from 100 KHz to 100 GHz.
At one time they would sell off-spec diodes to the experimenter for
dirt cheap. Last time I bought a NoiseCom diode was back when I was
spending Other Peoples' Money and didn't care the expense.
What I'm trying to make is a noise source fairly flat from roughly 1M
to 1G to use as a poor man's sweep generator to use with a spectrum
analyzer to examine various filter topologies.
My first thought was to use a zener or perhaps a hot carrier in
breakdown and amplify the noise using a cascade of two or three of the
little Mini-Circuits Labs mmics in series to get me up to some decent
power out -- say 0 dBm or so.
Got any other thoughts on how to generate flat noise to a Gig on the
cheap?
Jim
Phil Hobbs
Photocurrent shot noise. Get a 2.5 Gb/s PD off eBay and shoot a
milliwatt or two of light into it. The photocurrent noise is given by
the shot noise formula, so you know it a priori.
Cheers
Phil Hobbs
--
Dr Philip C D Hobbs
Principal
ElectroOptical Innovations
55 Orchard Rd
Briarcliff Manor NY 10510
845-480-2058
hobbs at electrooptical dot net
http://electrooptical.net
John Larkin
A small zener driving a MMIC chain should work. Can your spectrum
analyzer normalize?
But noise is noisy! How about a nice stable picket-fence spectrum, a
line every 50 MHz maybe, from an SRD or a fast logic gate?
An EclipsPlus gate, driven by a square wave, should make fairly flat
odd harmonics up to a GHz or so. Adjust the input frequency to cover
various ranges of interest.
John
RST Engineering
<pcdhSpamM...@electrooptical.net> wrote:
>
>Photocurrent shot noise. Get a 2.5 Gb/s PD off eBay and shoot a
>milliwatt or two of light into it. The photocurrent noise is given by
>the shot noise formula, so you know it a priori.
>
>Cheers
>
>Phil Hobbs
Would you elaborate just the littlest bit?
Jim
RST Engineering
<jjla...@highNOTlandTHIStechnologyPART.com> wrote:
>
>A small zener driving a MMIC chain should work. Can your spectrum
>analyzer normalize?
Normalize what?
>
>But noise is noisy! How about a nice stable picket-fence spectrum, a
>line every 50 MHz maybe, from an SRD or a fast logic gate?
That's not going to work so awfully well for a 21.4 MHz. IF filter
that is only 50 kHz wide to start with. I need instantaneous
bandwidth of a Gig or so. Now a line every 50 mHz. should work well
{;-)
>
>An EclipsPlus gate, driven by a square wave, should make fairly flat
>odd harmonics up to a GHz or so. Adjust the input frequency to cover
>various ranges of interest.
Never heard of EcipsPlus. Is it ECL?
Jim
John Larkin
<jwe...@gmail.com> wrote:
>On Sun, 29 Nov 2009 14:48:51 -0800, John Larkin
><jjla...@highNOTlandTHIStechnologyPART.com> wrote:
>
>
>>
>>A small zener driving a MMIC chain should work. Can your spectrum
>>analyzer normalize?
>
>Normalize what?
Newer ones can be fed a reference spectrum, remember it, and divide a
later spectrum by that. So if your signal (or noise) source isn't
flat, it can correct for that. Sweep the generator without the filter,
then with the filter, and divide (or subtract the logs.) We do this at
work with our Aeroflex.
This wouldn't work well with noise, I'm thinking. It would be fine for
a comb. A little division by zero never killed anybody.
>>
>>But noise is noisy! How about a nice stable picket-fence spectrum, a
>>line every 50 MHz maybe, from an SRD or a fast logic gate?
>
>That's not going to work so awfully well for a 21.4 MHz. IF filter
>that is only 50 kHz wide to start with. I need instantaneous
>bandwidth of a Gig or so. Now a line every 50 mHz. should work well
>{;-)
Well, get a spectrum analyzer with a tracking generator! Or buy a
cheap VCO and triangle sweep it with a function generator.
It will be hard to generate a GHz-wide noise source that has any
usable power density in a 50 mHz slice. If there's a microwatt in
every 50 mHz, you'll need a 20 kilowatt noise generator.
>
>>
>>An EclipsPlus gate, driven by a square wave, should make fairly flat
>>odd harmonics up to a GHz or so. Adjust the input frequency to cover
>>various ranges of interest.
>
>Never heard of EcipsPlus. Is it ECL?
Yes. Onsemi mostly, some Arizona Microtech and Micrel.
Analog Devices makes some comparators that have 40 ps edges. They
should generate combs well into the GHz range.
I once managed a survey of twisted-pairs in the NY subway system. I
designed a comb generator, 1 KHz to 200 KHz I recall, and had one guy
connect it to one end of a pair at one station, and another photograph
a spectrum analyzer screen at the other. That saved a lot of time.
Geez, I've done a lot of weird stuff.
John
Tim Williams
<jjlar...@highNOTlandTHIStechnologyPART.com> wrote:
> If there's a microwatt in
> every 50 mHz, you'll need a 20 kilowatt noise generator.
If it's mHz, shouldn't it be more like 20GW?
An EMP bomb should do. ;-)
Tim
Paul Hovnanian P.E.
>
> "Paul Hovnanian P.E." <pa...@hovnanian.com> wrote in message
> news:4B108274...@hovnanian.com...
> > Sorry. I thought this was a thread about our resident right wing nuts.
> >
> > Never mind.
>
> Ah, good point. They're a little slow for this application, but you might
> tempt some cryptologists into downloading their entropy. Run the archives
> through a hash function and you've got a lovely source of random numbers.
I'm afraid not. The string "leftist weenies" keeps popping up
repeatedly.
--
Paul Hovnanian mailto:Pa...@Hovnanian.com
------------------------------------------------------------------
Don't anthropomorphize computers. They hate that.
John Larkin
1e9 * 1e-6 / 0.05 = 20e3
John
John Larkin
<pa...@hovnanian.com> wrote:
>Tim Williams wrote:
>>
>> "Paul Hovnanian P.E." <pa...@hovnanian.com> wrote in message
>> news:4B108274...@hovnanian.com...
>> > Sorry. I thought this was a thread about our resident right wing nuts.
>> >
>> > Never mind.
>>
>> Ah, good point. They're a little slow for this application, but you might
>> tempt some cryptologists into downloading their entropy. Run the archives
>> through a hash function and you've got a lovely source of random numbers.
>
>I'm afraid not. The string "leftist weenies" keeps popping up
>repeatedly.
Ditto "straw man" and "peer-reviewed." It's pseudo-random, ie noise
generated by pseudo-intellectuals.
John
krw
<pa...@hovnanian.com> wrote:
>Tim Williams wrote:
>>
>> "Paul Hovnanian P.E." <pa...@hovnanian.com> wrote in message
>> news:4B108274...@hovnanian.com...
>> > Sorry. I thought this was a thread about our resident right wing nuts.
>> >
>> > Never mind.
>>
>> Ah, good point. They're a little slow for this application, but you might
>> tempt some cryptologists into downloading their entropy. Run the archives
>> through a hash function and you've got a lovely source of random numbers.
>
>I'm afraid not. The string "leftist weenies" keeps popping up
>repeatedly.
I didn't know you were a string.
Baron
Hey Phil, how do leds compare as noise sources ?
--
Best Regards:
Baron.
GregS
>This is an Elgenco 331A gaussian noise generator. I know very little about
>it, though I did see an ad in an old journal proclaiming it's good to four
>sigmas. It seems to be roughly "audio frequency", by which I mean, the
>circuits are audio quality, no particular attention paid to high or low
>frequency bandwidth (AC coupled, no peaking coils). I would guess 10Hz to
>200kHz or so.
I think I have a newer solid state unit. Glad. Mine has selectable BW.
greg
Joop
Ok, I'll try and collect some.
It will not be in the next days though.
Joop
John Larkin
George Herold
<jjlar...@highNOTlandTHIStechnologyPART.com> wrote:
Thanks for the pdf from the data book John, I think I saw similar
type stuff. I also put a cap across the zener and at low currents saw
that the pulse width seemed to depend on the capacitor value....(more
C = longer pulses) almost like the zener was a solid state 'spark gap'
that discharged all the charge that was availible. I want to look
into this again, But my boss put the kibash on these experiments and
I'll have to look into it 'after hours' or at home.
George H.