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

I have seen a small "gain of wheat" type light bulb used as a noise
source...

Feed it with DC through a choke and AC couple the noise out ....

and you can vary it too!!

Mark

Immediately you say "choke" you have modified and peaked the bandwidth.
I'll buy that you can feed it with a resistor for broadband, but in my
humble opinion the construction of a grain of wheat bulb won't get up into
the UHF region with noise. Do you have any idea of the output level of this
circuit?

Jim



"Mark" wrote in message
oups.com...
I have seen a small "gain of wheat" type light bulb used as a noise
source...

Feed it with DC through a choke and AC couple the noise out ....

and you can vary it too!!

Mark

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

"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

On Wed, 11 Jan 2006 14:53:07 -0600, "Tim Williams"
wrote:

"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

GR?

John

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

Try this
http://www.noisecom.com/

"RST Engineering (jw)" wrote in message
.. .
Immediately you say "choke" you have modified and peaked the bandwidth.
I'll buy that you can feed it with a resistor for broadband, but in my
humble opinion the construction of a grain of wheat bulb won't get up into
the UHF region with noise. Do you have any idea of the output level of
this circuit?

Jim



"Mark" wrote in message
oups.com...
I have seen a small "gain of wheat" type light bulb used as a noise
source...

Feed it with DC through a choke and AC couple the noise out ....

and you can vary it too!!

Mark

"John Larkin" wrote in message
...
I've got a gaussian noise generator, ...

GR?

Come again?

Tim

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