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

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

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.

I still like the flashlight/photodiode trick. You can get a really good
calibration just from the dc, and can calibrate the frequency response
with a spark plug.

Cheers,

Phil Hobbs

ORIGINAL MESSAGE:


"Phil Hobbs" wrote

snip
and can calibrate the frequency response with a spark plug.

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

I generally use a pipe wrench, but I'll try anything once.

Bill, W6WRT

Nice touch, Bill.
73, Steve, K9DCI

"Bill Turner" wrote in message
...
ORIGINAL MESSAGE:


"Phil Hobbs" wrote

snip
and can calibrate the frequency response with a spark plug.

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

I generally use a pipe wrench, but I'll try anything once.

Bill, W6WRT

On Wed, 11 Jan 2006 14:10:32 -0500, Phil Hobbs
wrote:

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

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.

I still like the flashlight/photodiode trick. You can get a really good
calibration just from the dc, and can calibrate the frequency response
with a spark plug.

Cheers,

Phil Hobbs


What's the light-flash waveform look like from a spark plug? What do
you drive it with?

Don't you have gobs of femtosecond lasers around your place?

John

John Larkin wrote:
On Wed, 11 Jan 2006 14:10:32 -0500, Phil Hobbs
wrote:


John Larkin wrote:

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

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.

I still like the flashlight/photodiode trick. You can get a really good
calibration just from the dc, and can calibrate the frequency response
with a spark plug.

Cheers,

Phil Hobbs



What's the light-flash waveform look like from a spark plug? What do
you drive it with?

Don't you have gobs of femtosecond lasers around your place?

John


You use one of the circular-gap plugs, run it to a HV supply via a 10M
resistor, and just discharge the capacitance of the plug--you get a nice
irregular relaxation oscillation. It isn't the absolute most beautiful
pulse, but (a) it's easy to shield so you get rid of the pickup, (b)
it's surprisingly bright, and (c) the rising edge is way under 1 ns,
which should be fine for the VHF to low UHF range. I might stick one on
my sampling scope sometime and find out more about its actual
performance, but this is a pretty common trick.

There are femtosecond lasers around here--my fastest one is about 20 ps,
but it's continuously tunable from 420 nm to 10 microns, when it's working.

Cheers,

Phil Hobbs

"John Larkin" wrote in message
news
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.

I've got a gaussian noise generator, some SS in the power supply, tubes
everywhere else, found it on the curb and apparently works. Uses a pair of
6D4 thyratrons in magnetic fields for the noise.

Tim

--
Deep Fryer: a very philosophical monk.
Website: http://webpages.charter.net/dawill/tmoranwms