Steve Nosko wrote:
. . .
Don't (some) zeners generate noise???...or is that only near the breakdown
reigion?

Some are very noisy. The noisiest I've seen have been ones in the 12 -
15 volt range when biased at considerably less than a mA. I've used one,
followed by a 50 ohm amplifier "pill" IC, as a broadband noise source to
see filter responses with a spectrum analyzer. The noise is easily
visible well up into the UHF region.

But all zeners generate some noise, so you have to use appropriate
filtering in sensitive applications. In my experience, though, band gap
references can be even noisier than a typical zener.

Roy Lewallen, W7EL

Roy ...

I've been playing around (ahem, excuse me, heuristically engineering) with
zener noise sources for a while using the same spectrum analyzer trick and
as yet I haven't been able to make the noise as "flat" across the passband
as I'd like. I've tried varying the bias, the voltage, and a few other
tricks, but as yet, no joy.

Can you shed some light on what you've found to make the noise power/voltage
fairly level across the band?

Jim




Some are very noisy. The noisiest I've seen have been ones in the 12 - 15
volt range when biased at considerably less than a mA. I've used one,
followed by a 50 ohm amplifier "pill" IC, as a broadband noise source to
see filter responses with a spectrum analyzer. The noise is easily visible
well up into the UHF region.

But all zeners generate some noise, so you have to use appropriate
filtering in sensitive applications. In my experience, though, band gap
references can be even noisier than a typical zener.

Roy Lewallen, W7EL

RST Engineering wrote...

Roy ...

I've been playing around (ahem, excuse me, heuristically engineering) with
zener noise sources for a while using the same spectrum analyzer trick and
as yet I haven't been able to make the noise as "flat" across the passband
as I'd like. I've tried varying the bias, the voltage, and a few other
tricks, but as yet, no joy.

Can you shed some light on what you've found to make the noise power/voltage
fairly level across the band?

Good zener noise sources are carefully bred and tested, they
do _not_ come naturally from garden-variety zener diodes. I
suggest you go read the hundred or so messages in the famous
zener oscillation thread a few years back here on s.e.d. In
this you'll learn of my substantial investigations into the
topic, some physics - and, very important, learn what a zener
microplasma is. You'll see my ASCII waveform plots of actual
bench measurements showing exactly what's going on. After all
this you may decide to avoid using zener diodes for calibrated
noise sources. Sorry about that!


--
Thanks,
- Win

...the famous zener oscillation thread a few years back
...my ASCII waveform plots of actual bench measurements
showing exactly what's going on.
Winfield Hill

http://groups.google.com/group/sci.e...lation&f wc=1

JeffM wrote...

...the famous zener oscillation thread a few years back
...my ASCII waveform plots of actual bench measurements
showing exactly what's going on.
Winfield Hill

http://groups.google.com/group/sci.e...lation&f wc=1

That's one thread, perhaps the first in a series. That thread
doesn't have the waveforms I was referring to (although there
are some waveforms in posts 51 and 66). Tony, Bill, Roy and I,
and some others here wasted masses of time on this subject over
a period of a few months, eight and a half years ago. We took
bench measurements, did calculations, found the scientific
literature (it was a subject that occupied physicists in the
late 50s, see posts 72-76), and we did plenty of speculation.


--
Thanks,
- Win

Winfield Hill wrote...

JeffM wrote...

Winfield Hill wrote...

...the famous zener oscillation thread a few years back
...my ASCII waveform plots of actual bench measurements
showing exactly what's going on.

http://groups.google.com/group/sci.e...lation&f wc=1

That's one thread, perhaps the first in a series. That thread
doesn't have the waveforms I was referring to (although there
are some waveforms in posts 51 and 66). Tony, Bill, Roy and I,
and some others here wasted masses of time on this subject over
a period of a few months, eight and a half years ago. We took
bench measurements, did calculations, found the scientific
literature (it was a subject that occupied physicists in the
late 50s, see posts 72-76), and we did plenty of speculation.

All of which led Roy McCammon to remark (post 90), "I'd have to
say that it is the best thread this year." He said that Aug 5th,
after 3 weeks of posts, and yet the followup threads in Aug and
Sept on the same topic were just as long, and perhaps even more
interesting. Ah, those were that days!


--
Thanks,
- Win

OK, then. A zener makes a poor noise source according to what I'm reading.
Noise.com used to sell off-spec diodes by the onesies for we poor peons to
play with, but for whatever reason that doesn't seem to be the case any
more.

Given that a zener (at whatever current) is a poor noise source, what is a
good source of electronic broadband noise from low HF through high UHF --
say, 5 to 500 MHz.? (No smart remarks about spark gaps.)

Jim



"Winfield Hill" wrote in message
...


We took
bench measurements, did calculations, found the scientific
literature (it was a subject that occupied physicists in the
late 50s, see posts 72-76), and we did plenty of speculation.

On Wed, 11 Jan 2006 10:08:19 -0800, "RST Engineering"
wrote:

OK, then. A zener makes a poor noise source according to what I'm reading.
Noise.com used to sell off-spec diodes by the onesies for we poor peons to
play with, but for whatever reason that doesn't seem to be the case any
more.

Given that a zener (at whatever current) is a poor noise source, what is a
good source of electronic broadband noise from low HF through high UHF --
say, 5 to 500 MHz.? (No smart remarks about spark gaps.)

Jim



A hot resistor.

How about a thermistor or a lamp filament that was 50 ohms at some
high temperature. You could heat it with DC, sense its
resistance/temp, and let it make noise, all in a single part.

Old vintage noise figure meters used gas tubes. And I think there was
a pencil tube that mounted in a waveguide and made shot noise.

And, of course, the old photomultiplier trick.

John

Jim wrote: "...what is a good source of electronic broadband noise
from low HF through high UHF -- say, 5 to 500 MHz.?"

A linear feedback shift register. Small, repeatable. 500MHz should be
no particular problem these days. (There's an idea for some IC
manufacturer...32 bits clocked at 1G/sec repeats every 4 seconds, which
would be OK, but I'd prefer 40 or more bits. Should fit nicely into a
5 pin SOT-23: power, gnd, reset, out, ...)

On Wed, 11 Jan 2006 10:08:19 -0800, "RST Engineering"
wrote:

OK, then. A zener makes a poor noise source according to what I'm reading.
Noise.com used to sell off-spec diodes by the onesies for we poor peons to
play with, but for whatever reason that doesn't seem to be the case any
more.

Given that a zener (at whatever current) is a poor noise source, what is a
good source of electronic broadband noise from low HF through high UHF --
say, 5 to 500 MHz.? (No smart remarks about spark gaps.)

We had this already yesterday in '97 and '98.
The internet does not forget anything, so watch your mouth :-)

http://groups.google.de/group/rec.radio.amateur.homebrew/browse_frm/thread/e072aa7cef573f99/9147bca6602ef8d1?lnk=st&q=Gerhard+Hoffmann+noise&r num=1&hl=de#9147bca6602ef8d1

But, my final solution was to buy an Agilent 346c.

regards, Gerhard