1N4007 varactors

[JE]

The common 1N4007 seem to work for HF but what is the max. frequency they
can be used as varactors?

And how about zener diodes?

JE

[Allodoxaphobia]

Post by JE
The common 1N4007 seem to work for HF but what is the max. frequency
they can be used as varactors?
And how about zener diodes?

I'd expect that all to depend on manufacturer (and, even, date code.)

HNY es 73
Jonesy

[Ken Scharf]

Post by JE
The common 1N4007 seem to work for HF but what is the max. frequency they
can be used as varactors?
And how about zener diodes?
JE

I suspect any si diode will work to some extent as a varicap or zener.
Not all diodes will be stable as zeners, the 1N506x series will probably
work better as a zeners than the 1n400x series. BTW the 1n5061 will work
as an 850v zener! Also the 1n4007 makes a good poor man's PIN diode for
switching rf.

[A***@nouce.bellatlantic.net]

Post by JE
The common 1N4007 seem to work for HF but what is the max. frequency they
can be used as varactors?

I've used them at low VHF, the limiting factor there is minimum
capacitance my be too high for some VHF uses.

Post by JE
And how about zener diodes?

As varicaps? Some are ok some very poor. You require a breakdown
voltage well above the applied bias.

Allison

[JE]

Maybe 2N4401 will work, I built some simple 1 transistor FM transmitters
that modulate the base.

If not, who sells dual varactors in small quantities?

JE

Post by A***@nouce.bellatlantic.net

Post by JE
The common 1N4007 seem to work for HF but what is the max. frequency
they can be used as varactors?

I've used them at low VHF, the limiting factor there is minimum
capacitance my be too high for some VHF uses.

Post by JE
And how about zener diodes?

As varicaps? Some are ok some very poor. You require a breakdown
voltage well above the applied bias.
Allison

[K7ITM]

Since the 1N4007 isn't a dual, why do you require a dual varactor? I'd
expect diodes specifically made to be varactors would have less
variation from part to part with respect to capacitance than would some
other random diode.

Have you tried Mouser (as Professor suggests) or DigiKey, or some of
the surplus places like MPJA?

I've heard that 1N4007s commonly make decent PIN diodes. If that's the
case, if they really are made as a PIN structure, I would think they'd
make lousy varactors. Wide-tuning-range varactors are commonly
"hyper-abrupt" junctions, NOT PINs.

Cheers,
Tom

[Professor]

Why not just use a varactor... as a varactor... LOL
They are available in small quanities at www.mouser.com searchword
"varactor"...

Professor
www.telstar-electronics.com

[Dr. Grok]

Maybe I'm confusing this with something else but I always thought 1N4007's
were 1000 V PIV, 1 A rectifiers.

I believe "any" diode has varactor characteristics to some extent but if you
need a varactor you'd be better off using one designed as a varactor.

Dr. G.

Post by JE
The common 1N4007 seem to work for HF but what is the max. frequency they
can be used as varactors?
And how about zener diodes?
JE

[Ken Scharf]

Post by Dr. Grok
Maybe I'm confusing this with something else but I always thought 1N4007's
were 1000 V PIV, 1 A rectifiers.
I believe "any" diode has varactor characteristics to some extent but if you
need a varactor you'd be better off using one designed as a varactor.
Dr. G.

Post by JE
The common 1N4007 seem to work for HF but what is the max. frequency they
can be used as varactors?
And how about zener diodes?
JE

All diodes exhibit varactor and zener traits but not all are stable
as such. All diodes when reverse biased exhibit a value of capacitance
across them. In most cases it's usually quite small, less than 5 to 10pf.
Increase the reverse bias and the capacitance goes down. At very high frequencies
the capacitance change is enough to make a useful tuning diode. If you need
a varactor to work at medium to high frequencies the tuning effect won't be
very useful and you should use a true varactor diode. Such diodes have
either larger areas, or thinner substrates to increase th capacitance.

Any diode will work as a Zener, the zener voltage is where the reverse breakdown
occurs. In a true Zener, the breakdown voltage is stable over a large range
of current without the diode self destructing. Using a common diode as a zener
requires limiting the reverse current to a small value, but if the current isn't
large enough the zener voltage won't be stable.

And yes the 1n4007 is a 1000 vpiv rectifier diode. It also makes a good
rf switching diode thanks to it's PIN like structure. It's also quite cheap.

[Roy Lewallen]

Post by Ken Scharf
All diodes exhibit varactor and zener traits but not all are stable
as such. All diodes when reverse biased exhibit a value of capacitance
across them. In most cases it's usually quite small, less than 5 to 10pf.
Increase the reverse bias and the capacitance goes down. At very high frequencies
the capacitance change is enough to make a useful tuning diode. If you need
a varactor to work at medium to high frequencies the tuning effect won't be
very useful and you should use a true varactor diode. Such diodes have
either larger areas, or thinner substrates to increase th capacitance.
. . .

Zener diodes have much more capacitance than this, with the amount of C
being greater as the zener voltage gets lower. It's been a long time
since I've looked at this, but as I recall you can get well over 100 pF
from something like a 5 V zener. For the same reason, reverse biased E-B
junctions can give quite a bit of C. Of course, the limited breakdown
voltage limits your tuning range. Higher power zeners have higher C yet.

I've used zeners for varicaps many times in HF rigs, to offset a VFO
when switching bands, and for RIT. Haven't tried one as the main tuning
capacitor, but I haven't tried a regular varicap, either.

Diodes specified for varicap use have more predictable
capacitance-vs-voltage characteristics, and you can get a variety of
different characteristics. They might have lower noise, too, but I've
never used one in an application where that was critical, so don't know
if that's the case. But for a lot of one-off projects, zeners work fine
as varicaps.

As for using something else as zeners, emitter-base junctions work well.
You don't get much variety, though -- most break down at around 5-6
volts. I've got a power supply I built over 30 years ago which uses a
couple of series transistor E-B junctions as the voltage reference. It's
still my main bench supply.

Roy Lewallen, W7EL

[JE]

It was just that they are dirt cheap and available.
I'll pony up for real ones.


JE

[A***@nouce.bellatlantic.net]

Post by JE
It was just that they are dirt cheap and available.
I'll pony up for real ones.
JE

I'd go with try it first.

Also base collector junction of many transistors is fairly decent
varactor. Low power transistors tend to be low capacitance
and the amount of capacitance increases with device dies size
(power level).

Allison

[Dr. Grok]

Zeners are also often used as noise sources, which might be a good reason NOT
to use them for the tuning, especially in a receiver.

Dr. G.

Post by Ken Scharf

Post by Ken Scharf
All diodes exhibit varactor and zener traits but not all are stable
as such. All diodes when reverse biased exhibit a value of capacitance
across them. In most cases it's usually quite small, less than 5 to 10pf.
Increase the reverse bias and the capacitance goes down. At very high

frequencies

Post by Ken Scharf
the capacitance change is enough to make a useful tuning diode. If you need
a varactor to work at medium to high frequencies the tuning effect won't be
very useful and you should use a true varactor diode. Such diodes have
either larger areas, or thinner substrates to increase th capacitance.
. . .

Zener diodes have much more capacitance than this, with the amount of C
being greater as the zener voltage gets lower. It's been a long time
since I've looked at this, but as I recall you can get well over 100 pF
from something like a 5 V zener. For the same reason, reverse biased E-B
junctions can give quite a bit of C. Of course, the limited breakdown
voltage limits your tuning range. Higher power zeners have higher C yet.
I've used zeners for varicaps many times in HF rigs, to offset a VFO
when switching bands, and for RIT. Haven't tried one as the main tuning
capacitor, but I haven't tried a regular varicap, either.
Diodes specified for varicap use have more predictable
capacitance-vs-voltage characteristics, and you can get a variety of
different characteristics. They might have lower noise, too, but I've
never used one in an application where that was critical, so don't know
if that's the case. But for a lot of one-off projects, zeners work fine
as varicaps.
As for using something else as zeners, emitter-base junctions work well.
You don't get much variety, though -- most break down at around 5-6
volts. I've got a power supply I built over 30 years ago which uses a
couple of series transistor E-B junctions as the voltage reference. It's
still my main bench supply.
Roy Lewallen, W7EL

[A***@nouce.bellatlantic.net]

Post by Dr. Grok
Zeners are also often used as noise sources, which might be a good reason NOT
to use them for the tuning, especially in a receiver.

In the breakdown region yes, in the revserse bias region no. I've
tried some .4w 22V Zeners and they are decent varactors save for
you need to keep far enough from the 22V and -.5V or they exhibit
their other charactersistics.

Allison

Post by Dr. Grok
Dr. G.

Post by Ken Scharf

Post by Ken Scharf
All diodes exhibit varactor and zener traits but not all are stable
as such. All diodes when reverse biased exhibit a value of capacitance
across them. In most cases it's usually quite small, less than 5 to 10pf.
Increase the reverse bias and the capacitance goes down. At very high

frequencies

Post by Ken Scharf
the capacitance change is enough to make a useful tuning diode. If you need
a varactor to work at medium to high frequencies the tuning effect won't be
very useful and you should use a true varactor diode. Such diodes have
either larger areas, or thinner substrates to increase th capacitance.
. . .

Zener diodes have much more capacitance than this, with the amount of C
being greater as the zener voltage gets lower. It's been a long time
since I've looked at this, but as I recall you can get well over 100 pF
from something like a 5 V zener. For the same reason, reverse biased E-B
junctions can give quite a bit of C. Of course, the limited breakdown
voltage limits your tuning range. Higher power zeners have higher C yet.
I've used zeners for varicaps many times in HF rigs, to offset a VFO
when switching bands, and for RIT. Haven't tried one as the main tuning
capacitor, but I haven't tried a regular varicap, either.
Diodes specified for varicap use have more predictable
capacitance-vs-voltage characteristics, and you can get a variety of
different characteristics. They might have lower noise, too, but I've
never used one in an application where that was critical, so don't know
if that's the case. But for a lot of one-off projects, zeners work fine
as varicaps.
As for using something else as zeners, emitter-base junctions work well.
You don't get much variety, though -- most break down at around 5-6
volts. I've got a power supply I built over 30 years ago which uses a
couple of series transistor E-B junctions as the voltage reference. It's
still my main bench supply.
Roy Lewallen, W7EL

[Roy Lewallen]

Post by Dr. Grok
Zeners are also often used as noise sources, which might be a good reason NOT
to use them for the tuning, especially in a receiver.

You mean that a zener diode biased at less than breakdown voltage
generates more noise than a diode specified for varactor use biased at
less than breakdown? I assume this noise would be in the form of time
jitter of the capacitance, since the leakage current would be very
small. Have you seen this in some specification, or is it from experience?

Roy Lewallen, W7EL

[Steve Nosko]

Dr. G,
You are correct, but many circuits have used the 1N4000 series diodes as
varactors with acceptable results. Any diode is a varactor (even transistor
junctions), but those called varactors are just optimized for and
measured/spec'ed as variable caps. If the cap value works in the circuit
and losses/noise/whatever-else aren't a problem, then no problem. I chalk
it up to: Some of us don't have the luxury of either well stocked basements
or pocket books, or perhaps the willingness to run out to the local parts
store (if you have one) and pick something out just to throw some neat
little thingy together.

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

73, Steve, K.9/D;C'I

Post by Dr. Grok
Maybe I'm confusing this with something else but I always thought 1N4007's
were 1000 V PIV, 1 A rectifiers.
I believe "any" diode has varactor characteristics to some extent but if you
need a varactor you'd be better off using one designed as a varactor.
Dr. G.

Post by JE
The common 1N4007 seem to work for HF but what is the max. frequency they
can be used as varactors?
And how about zener diodes?
JE

[Roy Lewallen]

Post by Steve Nosko
. . .
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

[RST Engineering]

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

[Winfield Hill]

RST Engineering wrote...

Post by RST Engineering
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!

[JeffM]

...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.electronics.design/browse_frm/thread/399b6a0bf6cfa4f5/16aa533d72a79d11?q=microplasma+zener+Oscillation&fwc=1

[Winfield Hill]

JeffM wrote...

Post by JeffM

...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.electronics.design/browse_frm/thread/399b6a0bf6cfa4f5/16aa533d72a79d11?q=microplasma+zener+Oscillation&fwc=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.

[Winfield Hill]

Winfield Hill wrote...

Post by Winfield Hill
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.electronics.design/browse_frm/thread/399b6a0bf6cfa4f5/16aa533d72a79d11?q=microplasma+zener+Oscillation&fwc=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!

[RST Engineering]

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" <***@newsguy.com> wrote in message news:***@drn.newsguy.com...


We took

Post by Winfield Hill
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.

[John Larkin]

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

Post by RST Engineering
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

[Phil Hobbs]

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

[Bill Turner]

ORIGINAL MESSAGE:


"Phil Hobbs" <***@SpamMeSenseless.pergamos.net 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

[Steve Nosko]

Nice touch, Bill.
73, Steve, K9DCI

Post by Bill Turner
<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]

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

Post by Phil Hobbs

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

[Phil Hobbs]

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

Post by Phil Hobbs

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

[Tim Williams]

Post by John Larkin
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

[John Larkin]

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

Post by Tim Williams

Post by John Larkin
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

[Tim Williams]

I've got a gaussian noise generator, ...

GR?

Come again?

Tim

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

[Mike Andrews]

Post by Tim Williams

I've got a gaussian noise generator, ...

GR?

Come again?

When I see "GR", I think "General Radio", and salivate gently. They
made some really, really nice test gear.

[Jim Thompson]

On Wed, 11 Jan 2006 23:47:37 +0000 (UTC), "Mike Andrews"

Post by Mike Andrews

Post by Tim Williams

I've got a gaussian noise generator, ...

GR?

Come again?

When I see "GR", I think "General Radio", and salivate gently. They
made some really, really nice test gear.

And then let themselves get sucked, by marketing, into large
mainframe-based testers, and lost their ass.

I watched the money-making portable test division in Phoenix get
trashed by the shit-heads in Massachusetts... now you know _part_ of
the source of my animosity toward Massa2shits ;-)

...Jim Thompson

[Winfield Hill]

Jim Thompson wrote...

Post by Jim Thompson
I watched the money-making portable test division in Phoenix
get trashed by the shit-heads in Massachusetts... now you know
_part_ of the source of my animosity toward Massa2shits ;-)

That's an amazing extension. Plenty of healthy Massachusetts
companies have been sucked dry by their out-of-state owners.
Obviously the ability to mis-manage a company from a distance
is not notably a Massachusetts sin, unless you're obsessed with
the Harvard Business School's modest influence on the issue.

[John Larkin]

On 11 Jan 2006 17:52:16 -0800, Winfield Hill

Post by Winfield Hill
Jim Thompson wrote...

Post by Jim Thompson
I watched the money-making portable test division in Phoenix
get trashed by the shit-heads in Massachusetts... now you know
_part_ of the source of my animosity toward Massa2shits ;-)

That's an amazing extension. Plenty of healthy Massachusetts
companies have been sucked dry by their out-of-state owners.
Obviously the ability to mis-manage a company from a distance
is not notably a Massachusetts sin, unless you're obsessed with
the Harvard Business School's modest influence on the issue.

It is sadly true that many of the old-line Rt 128 companies are
gone... DEC, Data General, GR, Sensitive Instruments, Clevite,
Transitron, probably others. Have others popped up to take their
place? Analog Devices, for sure.

John

[Allodoxaphobia]

Post by John Larkin
It is sadly true that many of the old-line Rt 128 companies are
gone... DEC, Data General, GR, Sensitive Instruments, Clevite,
Transitron, probably others.
Have others popped up to take their place?

Why sure. Can you red Chinese tech manuals?

[Allodoxaphobia]

Post by Allodoxaphobia

Post by John Larkin
It is sadly true that many of the old-line Rt 128 companies are
gone... DEC, Data General, GR, Sensitive Instruments, Clevite,
Transitron, probably others.
Have others popped up to take their place?

Why sure. Can you red Chinese tech manuals?

Funny how my Made-In-China keyboard with its @#%^$}# sticky "a" key
laid that out. :-\

[Winfield Hill]

John Larkin wrote...

Post by John Larkin

Post by Winfield Hill
Jim Thompson wrote...

Post by Jim Thompson
I watched the money-making portable test division in Phoenix
get trashed by the shit-heads in Massachusetts... now you know
_part_ of the source of my animosity toward Massa2shits ;-)

That's an amazing extension. Plenty of healthy Massachusetts
companies have been sucked dry by their out-of-state owners.
Obviously the ability to mis-manage a company from a distance
is not notably a Massachusetts sin, unless you're obsessed with
the Harvard Business School's modest influence on the issue.

It is sadly true that many of the old-line Rt 128 companies are
gone... DEC, Data General, GR, Sensitive Instruments, Clevite,
Transitron, probably others. Have others popped up to take their
place? Analog Devices, for sure.

We have scads of large wealthy "newer" high-tech companies
headquartered here, that you may not often hear of, like
Thermo Electron, Bruker, Summit Technology, EMC, etc., and
others you do know, with a substantial presence, like Agilent.

Many software and Internet companies are headquartered in MA,
like Peoplesoft, Novell, etc., and many others have a large
presence, like Sun, Red Hat, IBM, Microsoft, etc.

We all know scores of top-tier biotech companies with their
headquarters in MA, who have massive high-tech employment here.

[John Larkin]

On 12 Jan 2006 07:44:35 -0800, Winfield Hill

Post by Winfield Hill
We have scads of large wealthy "newer" high-tech companies
headquartered here, that you may not often hear of, like
Thermo Electron, Bruker, Summit Technology, EMC, etc., and
others you do know, with a substantial presence, like Agilent.

Ah, Bruker, my arch-enemy. I make the gradient drivers and temperature
controllers for Varian. I've also had bad experiences with Bruker AXS
in Madison. They both seem to be very NIH and very PhD oriented, so
they're hard to deal with and especially sell to.

John

[Tim Williams]

Post by Mike Andrews

I've got a gaussian noise generator, ...

GR?

When I see "GR", I think "General Radio", and salivate gently. They
made some really, really nice test gear.

Ah, had a feeling it was something about a manufacturer...

Unfortunately(?) no, it appears to be Elgenco, and I also now remember not
finding much info on this device after I picked it up. It's a rack mount
unit BTW.

Tim

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

[John Larkin]

On Wed, 11 Jan 2006 17:00:09 -0600, "Tim Williams"

Post by Tim Williams

I've got a gaussian noise generator, ...

GR?

Come again?
Tim

Is it a General Radio noise generator? I have an old GR noise
generator, and the manual talks about moving the magnet around to
optimize something.

John

[K7ITM]

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, ...)

[Gerhard Hoffmann]

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

Post by RST Engineering
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&rnum=1&hl=de#9147bca6602ef8d1>

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

regards, Gerhard

[Robert Baer]

Post by RST Engineering
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
We took

Post by Winfield Hill
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.

Wouldn't a zener running in (or near) the (easily seen on curve
tracer) negative resistance mode have lots of noise?

[Ken Smith]

In article <h0mxf.1698$***@newsread1.news.pas.earthlink.net>,
Robert Baer <***@earthlink.net> wrote:
[...]

Post by Robert Baer
Wouldn't a zener running in (or near) the (easily seen on curve
tracer) negative resistance mode have lots of noise?

There's noise and then there's noise. Any signal we don't want we call
noise. A noise source for instumentation needs to have a flat spectrum.
The noise on a zener is a good example of the former and poor example of
the latter.

[Roy Lewallen]

Post by Winfield Hill
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. . .

For the record, that was Roy McCammon, not me.

Roy Lewallen, W7EL

[Roy Lewallen]

Post by RST Engineering
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?

It's not particularly flat over the whole band, and I haven't attempted
to make it be. My interest has been mostly in relatively narrow band
filters, or the shape of a main filter rolloff. The noise is adequately
flat over the bandwidths I've been interested in. It's been a while
since I've fooled with it, but as I recall, the shape of the noise
spectral distribution changed all over the map as I changed the diode
bias. I imagine that it changes with temperature and with individual
diodes, too. So any circuit used to flatten it would only work for a
particular diode, current, and probably temperature. The bottom line is
that it's probably a lousy way to try to generate a flat broadband noise
spectrum.

Roy Lewallen, W7EL

[Sjouke Burry]

Post by RST Engineering
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

What I did for some project which needed equal amplitude
uncorrelated noise,is amplify the zener noise with a wide
band video opamp,with high pass and lowpass filtering.
Used the low pass as input for a zero cross detector,
delayed the zerocrossing 10 microseconds,and used that
for clock to a circulating bit in a shift register.
each parallel output of that register controlled a
sample/hold opamp,sampling the highpass signal.
Voila!! 8 audio frequency, non-correlated noise sources.
The zerocrossing clock was made this way,to avoid detectable
clock tones int the output.(2 to 20 microsec between
crossings)
the 10 microsecond delay was used to get a voltage at
the sample and hold opamp which was not correlated to the
zerocrossing.
If you need only one signal ,leave out the shift register,
and just use a 10 and a 1 microsec. oneshot for the s/h
opamp clock.
The application? A wind and engine noise generator for a
car simulator.

[John Larkin]

On Tue, 10 Jan 2006 14:30:01 -0800, "RST Engineering"

Post by RST Engineering
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

These folks will sell you serious noise diodes...

http://www.noisecom.com/NC/default.htm

John

[Mark]

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

[RST Engineering (jw)]

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

Post by Mark
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

[Clark]

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

Post by RST Engineering (jw)
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

Post by Mark
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

[RST Engineering]

I've used noisecom for some years, but they are hard to buy in
onesie-twosies and are rather expensive in quantity when you only need one.

They USED to sell seconds that didn't meet spec, but I don't see that offer
on their current website.

Jim

Post by Clark
Try this
http://www.noisecom.com/

[Clark]

Just ask for samples, I got five of them a few years ago.

Post by RST Engineering
I've used noisecom for some years, but they are hard to buy in
onesie-twosies and are rather expensive in quantity when you only need one.
They USED to sell seconds that didn't meet spec, but I don't see that
offer on their current website.
Jim

Post by Clark
Try this
http://www.noisecom.com/

[Mark]

depends upon the resistance and temperature of the filament

a small grain of wheat bulb will work to 500 MHz..


Mark

[John Popelish]

Steve Nosko wrote:
(snip)

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

I think that whether noisy or not, the noise generation mechanism
kicks in, only when the zeners are reverse conducting via the zener
breakdown process, so if you keep the voltage well below the zener
knee, say, half of that, they are not particularly noisy compared to
other diodes. So, yes, only near the breakdown region, especially
just below the rated voltage (low reverse current).

[Asimov]

"John Popelish" bravely wrote to "All" (10 Jan 06 22:14:12)
--- on the heady topic of "Re: 1N4007 varactors"

JP> From: John Popelish <***@rica.net>
JP> Xref: core-easynews rec.radio.amateur.homebrew:90859

JP> Steve Nosko wrote:
JP> (snip)

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

JP> I think that whether noisy or not, the noise generation mechanism
JP> kicks in, only when the zeners are reverse conducting via the zener
JP> breakdown process, so if you keep the voltage well below the zener
JP> knee, say, half of that, they are not particularly noisy compared to
JP> other diodes. So, yes, only near the breakdown region, especially
JP> just below the rated voltage (low reverse current).


I never tested a zener when used as varactor but I think these have a
much greater reverse saturation current (even far below breakdown
threshold) and it is this that might cause comparatively more noise
than a conventional diode with a tiny leakage current. Well, at least
that is what the junction noise equations would seem to indicate.

A*s*i*m*o*v

[Highland Ham]

Post by Asimov
I never tested a zener when used as varactor but I think these have a
much greater reverse saturation current (even far below breakdown
threshold) and it is this that might cause comparatively more noise
than a conventional diode with a tiny leakage current. Well, at least
that is what the junction noise equations would seem to indicate.

==============================
Zener diodes are often used as wide band 'noise generators'for use in an
impedance bridge used in conjunction with a receiver.

Frank KN6WH / GM0CSZ

[Asimov]

"Highland Ham" bravely wrote to "All" (11 Jan 06 09:47:40)
--- on the heady topic of "Re: 1N4007 varactors"

HH> From: Highland Ham <***@dsl.pipex.com>
HH> Xref: core-easynews rec.radio.amateur.homebrew:90890

HH> Zener diodes are often used as wide band 'noise generators'for use in
HH> an impedance bridge used in conjunction with a receiver.

I understand to generate the noise that the zener diodes are operated
within their normal breakdown current range. However, as a varactor it
isn't desirable to have a breakdown current flow. The only tiny
current that flows is a saturation current which is related to
setting up the P-N junction boundaries within the semiconductor.

M*i*k*e

[Roy Lewallen]

Post by Asimov
I never tested a zener when used as varactor but I think these have a
much greater reverse saturation current (even far below breakdown
threshold) and it is this that might cause comparatively more noise
than a conventional diode with a tiny leakage current. Well, at least
that is what the junction noise equations would seem to indicate.

They also have a whale of a lot more capacitance than a conventional
diode. So I don't think it's a fair comparison.

Roy Lewallen, W7EL

[John Popelish]

Post by Roy Lewallen

Post by Asimov
I never tested a zener when used as varactor but I think these have a
much greater reverse saturation current (even far below breakdown
threshold) and it is this that might cause comparatively more noise
than a conventional diode with a tiny leakage current. Well, at least
that is what the junction noise equations would seem to indicate.

They also have a whale of a lot more capacitance than a conventional
diode. So I don't think it's a fair comparison.

Okay, if we are discussing strange and high capacitance varactors,
what would you think of using a PIN photo diode as a varactor? They
have more chip area per dollar and per package size and capacitance
than many rectifier diodes, and that are made to have low leakage
current and often have low inductance packaging.
For example:
http://rocky.digikey.com/WebLib/Osram/Web%20Data/bpw34fa_fas.pdf
looks like a nice 15 to 70 pF capacitor.

I guess you would have to keep them in the dark, unless you wanted to
tune them (biased by a high resistance to a fixed voltage) with a
variable intensity light beam.

[Saandy , 4Z5KS]

...impossible to tell! nobody ever characterized them for high
frequency use. the usual effects of the varactor are pernicious! they
are crucial for low phase noise of the VCO using them. the only truly
effective way to check is build one and measure the performance with a
spectrum analyzer or a phase noise meter, both expensive items. my
recommendation is to build one and try to listen to its signal on a
receiver (stable one!), if the note is clean and not ragged it's OK. if
not the VCO is too noisy for use. don't be afraid to check more than
one diode in the same circuit. experience has shown that some units
perform better than others.
Saandy 4Z5KS

Post by JE
The common 1N4007 seem to work for HF but what is the max. frequency they
can be used as varactors?
And how about zener diodes?
JE