klystron vs. magnetron

[Christopher Zoeller]

As a newbie to the radar world, I have at least two questions:

1) What's the difference between a klystron and a magnetron?

2) What are the applications of each and why would one be
chosen over the other?

Thanks for any help -- it's very much appreciated!!!!!!!

Chris Zoeller

[James P. Meyer]

On Wed, 20 Nov 1996, Christopher Zoeller wrote:

> As a newbie to the radar world, I have at least two questions:
>
> 1) What's the difference between a klystron and a magnetron?
>
> 2) What are the applications of each and why would one be
> chosen over the other?

A klystron is an almost "normal" vacuum tube with the input and
output structures replaced by resonant cavities. A klystron can have
internal (or external) feedback built into its design so that it
functions as an oscillator, or it can be a simple amplifier.

A magnetron is quite different from a "normal" tube in that the
electron beam is forced by an external magnetic field to follow a spiral
path from the cathode to the anode, and a magnetron must operate as an
oscillator only.

Jim

[Jerry Codner]

Good answer.

Jerry Codner
gco...@lightlink.com

[Jerry Codner]

Christopher Zoeller wrote:
>
> As a newbie to the radar world, I have at least two questions:
>
> 1) What's the difference between a klystron and a magnetron?
>
> 2) What are the applications of each and why would one be
> chosen over the other?
>

> Thanks for any help -- it's very much appreciated!!!!!!!
>
> Chris Zoeller

There is a good answer for the first question floating around
elsewhere.

A klystron is used when a narrowband, high power, stable amplifier
is needed. They are used in radar, TV transmitters, particle
accelerators and other places.

Magnetrons are used in microwave ovens since they are cheap and
simple to operate. There they operate at 2.45 GHz. High power (10
kilowatt) magnetrons are used in industrial RF heating applications.
These operate at 900 MHz or 2.45 GHz. Very high power (1 Megawatt)
tubes are still used in some radars, such as the FPS-16. They
operate at 10 GHz. The 1 MW magnetrons are pulsed. For coherent
applications, an oscillator must be phase locked to the tube's
output on each pulse, since the magnetron starts oscillating at a
random phase at start-up.

A cross-field amplifier is basically a magnetron modified to accept
some input RF to make it oscillate at the right frequency. It can
be and is used as an amplifier in radar systems.

Jerry Codner
gco...@lightlink.com

[Bob Armstrong]

Christopher Zoeller wrote:
>
> As a newbie to the radar world, I have at least two questions:
>
> 1) What's the difference between a klystron and a magnetron?
>
> 2) What are the applications of each and why would one be
> chosen over the other?
>
> Thanks for any help -- it's very much appreciated!!!!!!!
>
> Chris Zoeller

In very general terms by the nature of their design, a klystron
is used as an RF amplifier while a magnetron is limited to use
as an RF oscillator. In the early days of radar (1950's era) some
special purpose klystrons were used as oscillators in some very
unique applications.

Regards,

Bob Armstrong
E-Mail: fca...@gnc.net
Home page: http://dune.globe-net.net/~fcaeng/
"Man does not live by RF alone."

[Thomas Pappano]

Bob Armstrong (fca...@gnc.net) wrote:

Can't help but throw in my two cents also :-)

Klystron anps and oscillators were in common use during WWII. The
Sperry/Raytheon 723/2K25 was used as a local oscillator for 10GHZ
radar. Some others like the 2K26 were used for lower bands. These
two are `reflex' klystrons which mean (if I recall correctly) that
they function as an oscillator with without providing a feedback loop
and their output is available on a coaxial or waveguide terminal.
Klystron amps have a seperate input and output termination and can
be set up as amplifiers or oscillators. A klystron puts out a
signal as clean and pure as its power source and is very easy to
frequency modulate for voice/data/etc and/or AFC. Klystrons of
higher outputs were used for telephone microwave, the old
Stevenson police radars (10GHZ/250mw), mobile/remote TV links etc.

Magnetrons are a specialized diode that operates in the influence of
a magnetic field and usually have integral resonant circuitry that
defines the frequency band they run in. They
are used in pulsed applications such as
pulse radar and also in continuous wave applications like microwave
ovens. There used to be magnetron tubes thich looked like ordinary
vacuum tubes but utilized external L and C to complete the oscillator
circuit and ran at low frequencies (although I never understood what
they were useful for!)

Rembering many burned fingers from hot 2k25's
Tom Pappano tpap...@galstar.com

[Thomas N. Lockyer]

In article <57bf57$7...@mercury.galstar.com> tpap...@galstar.com (Thomas Pappano) writes:
>From: tpap...@galstar.com (Thomas Pappano)
>Subject: Re: klystron vs. magnetron
>Date: 25 Nov 1996 06:42:47 GMT

> (snip)

Yes, you are dating yourself. I was an AETM3/c in the Navy and also remember
those local oscillators. Yes, they had a bellows that was externally
adjusted to cause the separation between grids that coupled to a resonant
chamber as reflex. BTW, can you still get those tubes? They had an octal
socket with a lead that extended into the waveguide and you just applied
voltage to get them to oscillate.

>Rembering many burned fingers from hot 2k25's
>Tom Pappano tpap...@galstar.com

Regards: Tom: http://www.best.com/~lockyer

[Jeff Layman]

On 15/07/2014 14:33, rra...@lakeheadu.ca wrote:

> On Monday, November 25, 1996 3:00:00 AM UTC-5, Thomas N. Lockyer wrote:
>> In article <57bf57$7...@mercury.galstar.com> tpap...@galstar.com (Thomas Pappano) writes:
>>> From: tpap...@galstar.com (Thomas Pappano)
>>> Subject: Re: klystron vs. magnetron
>>> Date: 25 Nov 1996 06:42:47 GMT

(snip)

> Yes you can still get those tube's, Toshiba sells them for about quarter mill.

Has the price gone up or down in the 18 years since the post you replied
to was made?

--

Jeff

[Jan Panteltje]

On a sunny day (Fri, 18 Jul 2014 18:28:51 +0100) it happened Jeff Layman
<JMLa...@invalid.invalid> wrote in <lqblgi$c6v$1...@news.albasani.net>:

http://www.ebay.com/sch/i.html?_trksid=p2050601.m570.l1313.TR0.TRC0.H0.Xklystron&_nkw=klystron&_sacat=0&_from=R40

208 hits, cheapest on top of page 1:
QKK753 Reflex Klystron tube NOS $18.95

[jrwal...@gmail.com]

On Monday, 25 November 1996 08:00:00 UTC, Thomas Pappano wrote:

> Magnetrons are a specialized diode that operates in the influence of
> a magnetic field and usually have integral resonant circuitry that
> defines the frequency band they run in. They
> are used in pulsed applications such as
> pulse radar and also in continuous wave applications like microwave
> ovens.

Every microwave oven I have looked at (with an antenna and diode detector) is pulsed. I think each pulse lasts around 100us with a repetition rate of 100Hz (in the UK) at full power. In low-power modes the pulse repetition rate is reduced but the peak power is unchanged.

The frequency is unstable, so as the turntable rotates with a slightly asymmetric load the frequency drifts up and down (within the ISM band)

John

[Tim Wescott]

Can we hand out awards for most years elapsed between question and
answer? Nearly 18 years may not be a record, but it's pretty good, all
in all.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

[govinds...@gmail.com]

derivations for klystron and magnatrons

[govinds...@gmail.com]

nice information and thanx

[meow...@care2.com]

On Monday, July 21, 2014 10:04:24 AM UTC+1, jrwal...@gmail.com wrote:
> On Monday, 25 November 1996 08:00:00 UTC, Thomas Pappano wrote:

> > Magnetrons are a specialized diode that operates in the influence of
> > a magnetic field and usually have integral resonant circuitry that
> > defines the frequency band they run in. They
> > are used in pulsed applications such as
> > pulse radar and also in continuous wave applications like microwave
> > ovens.

> Every microwave oven I have looked at (with an antenna and diode detector) is pulsed. I think each pulse lasts around 100us with a repetition rate of 100Hz (in the UK) at full power.

I didnt know that

> In low-power modes the pulse repetition rate is reduced but the peak power is unchanged.

Surely that is not the case. Almost 100% of nukes periodically switch magnetron power on and off to achieve lower mean cooking power. This would not cause the above to happen.

> The frequency is unstable, so as the turntable rotates with a slightly asymmetric load the frequency drifts up and down (within the ISM band)
> John

I thought the frequency was determined by the physical dimensions of the thing. The anode does run red hot, so dimensions will change slightly but surely not much, and presumably not up & down.


NT

[RobertMacy]

say what?! here i the US the microwave ovens I've seen have a single peak
rectifier diode that when you get near that peak the thing starts
operating near 2.5GHZ and simply 'smears' around until the voltage drops
too low. Completely half-wave 60 cycle AC mains related spikes.

If you sit up in the hills with an antenna and a spectrum analyzer you can
see three distinct phasings of microwave energy surging up at lunch and
dinner times!

[jrwal...@gmail.com]

On Friday, 26 September 2014 14:59:34 UTC+1, meow...@care2.com wrote:

> I thought the frequency was determined by the physical dimensions of the thing. The anode does run red hot, so dimensions will change slightly but surely not much, and presumably not up & down.
>

The load has an effect on the frequency. As the turntable rotates the loading on the magnetron changes (unless the food is perfectly symmetric) and the frequency drifts up and down in synchronism with the turntable rotation. This is real - it shows very clearly on a spectrum analyzer. However, the drift is not (quite) large enough to take the frequency outside the ISM band. It is enough to nmake it hard for other devices to avoid it.

John

[meow...@care2.com]

> say what?! here i the US the microwave ovens I've seen have a single peak
> rectifier diode that when you get near that peak the thing starts
> operating near 2.5GHZ and simply 'smears' around until the voltage drops
> too low. Completely half-wave 60 cycle AC mains related spikes.

that's quite different to jrwal's take on things. I cant think of any reason why the power pulses would be 100uS apiece. Its a thermionic doide at the end of the day, with magnetically corkscrewed electron path.


NT

[artie]

In article <21c83d7f-03d0-48e9...@googlegroups.com>,

Many Wifi vendors (Cisco and Aruba for example) have the capability to
identify interfering signals in the 2.4 GHz band, and microwave ovens
are a big culprit. The idea in these WiFi systems is to identify the
culprit and move traffic off the compromised channels. Microwave oven
spectrums are wobbly but identifiable.

Frequency varies with respect to anode voltage and load. Older
microwave ovens use half-wave rectified mains, so anode voltage varies,
and so does the oscillating frequency as the magnetron breaks into
oscillation, the frequency shifts as the voltage increases to its peak
in the (half) cycle, shifts with the load, and shifts again as the
anode voltage decreases with the half cycle until it drops out of
oscillation. As my Old Crow father-in-law said, clean and stable as a
tin whistle.

A number of years ago some microwave vendors switched from the bulky
transformer to switching supplies (they call them inverter ovens).
These run the magnetron on more stable DC, producing an operating
spectrum that's quite different from the older iron-core designs. More
parts, but much lighter, probably saving an incredible amount in
shipping. Marketed as more efficient as well.

[RobertMacy]

On Fri, 26 Sep 2014 10:06:53 -0700, artie <art...@gnospammail.com> wrote:

>> ...snip...

> Many Wifi vendors (Cisco and Aruba for example) have the capability to
> identify interfering signals in the 2.4 GHz band, and microwave ovens
> are a big culprit. The idea in these WiFi systems is to identify the
> culprit and move traffic off the compromised channels. Microwave oven
> spectrums are wobbly but identifiable.
>
> Frequency varies with respect to anode voltage and load. Older
> microwave ovens use half-wave rectified mains, so anode voltage varies,
> and so does the oscillating frequency as the magnetron breaks into
> oscillation, the frequency shifts as the voltage increases to its peak
> in the (half) cycle, shifts with the load, and shifts again as the
> anode voltage decreases with the half cycle until it drops out of
> oscillation. As my Old Crow father-in-law said, clean and stable as a
> tin whistle.
>
> A number of years ago some microwave vendors switched from the bulky
> transformer to switching supplies (they call them inverter ovens).
> These run the magnetron on more stable DC, producing an operating
> spectrum that's quite different from the older iron-core designs. More
> parts, but much lighter, probably saving an incredible amount in
> shipping. Marketed as more efficient as well.

The old microwave ovens actually were turned off for at least half the AC
cycle, giving wifi time to get in there and do their thing. Even if you
had two ovens on different phasing, you still had some garranteed time
slot where both were off. But if you say the new ovens use aan AC/DC
converter and are operating 100% once turned on, then such a robust
transmitter can easily swamp the AGC of any cheap wifi receiver's front
end. With NO break in the oven's transmission how can a wireless signal
get through over that ISM band?

[Maynard A. Philbrook Jr.]

In article <op.xmth85pm2cx0wh@ajm>, robert...@gmail.com says...

I would be a little concern if my nuker was overriding my Wifi that was
at least 3 feet or more away..

I have an inverter microwave so I don't know if that qualifies however,
I do know that my phone's Wifi works fine while I am standing there
waiting for my food no more than 3 feet away playing on the Inet.

Jamie

[Phil Allison]

artie wrote:

> Older microwave ovens use half-wave rectified mains,

** That is not very well expressed.

The vast majority of Microwave ovens use a large, iron core step up transformer feeding a high voltage diode stack plus a high voltage film cap to produce the circa 4kV supply for the magnetron. The schem is a kind of full wave voltage doubler with the magnetron itself acting as one of the needed diodes.

Sure, the magnetron only conducts and generates microwave energy during alternate half cycles of the AC supply - however, the current drawn from the AC outlet is smooth and continuous over the whole cycle.

This is unlike most DC supplies from AC where current is drawn only during the voltage peaks.


... Phil

[Jasen Betts]

On 2014-09-26, meow...@care2.com <meow...@care2.com> wrote:
> On Monday, July 21, 2014 10:04:24 AM UTC+1, jrwal...@gmail.com wrote:
>> In low-power modes the pulse repetition rate is reduced but the peak power is unchanged.
>
> Surely that is not the case. Almost 100% of nukes periodically
> switch magnetron power on and off to achieve lower mean cooking power.
> This would not cause the above to happen.

switching from 500 pulses per 10 seconds to 200 pulses per 10 seconds
could be seen as a reduction in the repitition rate. But yeah, it's
it's doing 2 seconds on three seconds off.




--
umop apisdn


--- news://freenews.netfront.net/ - complaints: ne...@netfront.net ---

[josephkk]

Magnetrons are a bit thresholdy on cathode - anode voltage. If there
isn't enough, no rf out.

?-)

[Tom Gardner]

On 27/09/14 01:05, Maynard A. Philbrook Jr. wrote:
> I would be a little concern if my nuker was overriding my Wifi that was
> at least 3 feet or more away..

Last time I looked, which was when WLANs existed but 802.11x WLANs
did not, the received wisdom was that you could expect up to 1W of
leakage from an old poorly maintained microwave oven. Yup, 1000mW.

I've taught my daughter not to peer in at cooking food, since
that means her most sensitive part, the cornea, is too near the
door for comfort.

[meow...@care2.com]

Pre-1980 nukes with missing carbon rubber door seals are rare.


NT

[RobertMacy]

if you do the SAR estimate, not too bad

also the body has an incredible way of cooling itself, even from localized
heating. but true that the eye parts are a bit more isolated.

[Tom Gardner]

The cornea is the worst, because the results are visible
(literally) and it has a poor blood supply. That's
why it was the test case for heating damage caused by mobile
phones.

[Tom Gardner]

True, but what makes you think modern designs are well cleaned
and well maintained? Think of down-market takeaways, for example.
(And up-market restaurants are always being done for food hygiene
infractions, which predisposes me to think they wouldn't take
too much care of their microwave ovens.)

[meow...@care2.com]

I thought part of the point of the modern choke design is they dont need to be cleaned/checked/maintained to work.

Even if a nuke did put out 1w, and all of it fired frontwards, what would a cornea absorb? A small fraction of a small fraction of a watt, amounting to under 0.1C temp rise.


NT

[dagmarg...@yahoo.com]

On Saturday, September 27, 2014 10:48:31 AM UTC-4, Tom Gardner wrote:
> On 27/09/14 14:22, RobertMacy wrote:
>

> > On Sat, 27 Sep 2014 01:41:49 -0700, Tom Gardner wrote:

> >> Last time I looked, which was when WLANs existed but 802.11x WLANs
> >> did not, the received wisdom was that you could expect up to 1W of
> >> leakage from an old poorly maintained microwave oven. Yup, 1000mW.
> >>
> >> I've taught my daughter not to peer in at cooking food, since
> >> that means her most sensitive part, the cornea, is too near the
> >> door for comfort.
> >>
> >
> > if you do the SAR estimate, not too bad
> >
> > also the body has an incredible way of cooling itself, even from localized heating. but true that the eye parts are a bit more isolated.
>
> The cornea is the worst, because the results are visible
> (literally)

Yes.

> and it has a poor blood supply.

The cornea has no vessels. It relies on the vessels inside the eyelid.

> That's why it was the test case for heating damage caused by mobile
> phones.

The main reason the cornea is susceptible is that GHz RF doesn't
penetrate the deep tissues--skin effect.

If you can't feel any RF heating with the back of your hand (good heat
sensitivity), I rather doubt it's a problem.

Cheers,
James Arthur

[Maynard A. Philbrook Jr.]

In article <95172049-db8b-46ea...@googlegroups.com>,
dagmarg...@yahoo.com says...

> > and it has a poor blood supply.
>
> The cornea has no vessels. It relies on the vessels inside the eyelid.
>
> > That's why it was the test case for heating damage caused by mobile
> > phones.
>
> The main reason the cornea is susceptible is that GHz RF doesn't
> penetrate the deep tissues--skin effect.
>
> If you can't feel any RF heating with the back of your hand (good heat
> sensitivity), I rather doubt it's a problem.
>
> Cheers,
> James Arthur
>

Is that your choice of tools to measure microwave leakage?

Jamie

[meow...@care2.com]

On Saturday, September 27, 2014 11:21:27 PM UTC+1, dagmarg...@yahoo.com wrote:
> On Saturday, September 27, 2014 10:48:31 AM UTC-4, Tom Gardner wrote:
> > On 27/09/14 14:22, RobertMacy wrote:
> > > > On Sat, 27 Sep 2014 01:41:49 -0700, Tom Gardner wrote:

> The cornea has no vessels. It relies on the vessels inside the eyelid.

> > That's why it was the test case for heating damage caused by mobile
> > phones.

> The main reason the cornea is susceptible is that GHz RF doesn't
> penetrate the deep tissues--skin effect.

it does. Microwave cooking penetrates a fair distance into the food, peak heating does not occur on the outer surface.


NT

[Neon John]

On Sat, 27 Sep 2014 15:48:31 +0100, Tom Gardner
<spam...@blueyonder.co.uk> wrote:

>The cornea is the worst, because the results are visible
>(literally) and it has a poor blood supply. That's
>why it was the test case for heating damage caused by mobile
>phones.

The risk is highly overstated.

http://www.neon-john.com/images/micronuke.jpg

John
John DeArmond
http://www.neon-john.com
http://www.fluxeon.com
Tellico Plains, Occupied TN
See website for email address

[dagmarg...@yahoo.com]

On Saturday, September 27, 2014 7:46:43 PM UTC-4, Maynard A. Philbrook Jr. wrote:

> dagmargoo...@yahoo.com says...

>
> > > and it has a poor blood supply.
> >
> > The cornea has no vessels. It relies on the vessels inside the eyelid.
> >
> > > That's why it was the test case for heating damage caused by mobile
> > > phones.
> >
> > The main reason the cornea is susceptible is that GHz RF doesn't
> > penetrate the deep tissues--skin effect.
> >
> > If you can't feel any RF heating with the back of your hand (good heat
> > sensitivity), I rather doubt it's a problem.
> >

> Is that your choice of tools to measure microwave leakage?

No. But if it doesn't *warm* your hand is it going to *cook* your
cornea? Highly doubtful.

Cheers,
James Arthur

[dagmarg...@yahoo.com]

That's a good point; flesh isn't all that conductive, so the skin-effect
isn't limiting and microwaves can travel deeper.

I stand corrected. Thanks.

Accordingly, the cornea intercepts only a fraction of the incident
microwave energy and will experience a lower temp rise than if it
absorbed all the microwave energy.

That makes it even harder to understand how something you couldn't
feel on your skin could somehow cook your corneas.

James Arthur

[RobertMacy]

On Sat, 27 Sep 2014 21:30:04 -0700, <dagmarg...@yahoo.com> wrote:

>> ....snip....

> I stand corrected. Thanks.
>
> Accordingly, the cornea intercepts only a fraction of the incident
> microwave energy and will experience a lower temp rise than if it
> absorbed all the microwave energy.
>
> That makes it even harder to understand how something you couldn't
> feel on your skin could somehow cook your corneas.
>
> James Arthur

WAIT! first if you inject energy [heat rise] INTO something the
distributed effect is that inside where something is getting hotter next
to something getting even hotter, of course the internal temp rises! the
outside will ALWAYS be cooler. Plus, as the water heats, evaporates, the
energy can go in further, and so on.

Next, most uWave ovens operate at 2.5GHz, the old RADAR ranges were at
what? 1.9GHZ, closer to the frequency of a water molecule bond. Radar
ranges tended to heat only the water molecule, thus they were more known
for dessicating instead of 'cooking'; going up to 2.5GHz has the advantage
of also heating the protein and fatty molecules so food cooks a bit better.

HOWEVER, there is still a decided skin effect in a water soaked something
being heated in a microwave. The outside edges get most of the heat
energy, but the 'captured' interior appears to heat more. to 'see' skin
depth in a microwave, scramble an egg, place in a shallow dish, and watch
as the ring of cooked egg progresses from the outside to the inside.

FWIW, the human body is like a bag of sea water in conductivity. Even
40kHz just penetrates. For uWave, the skin depth of 2.5GHz into flesh,
assuming a conductivity of 100 S/m [copper is 58 MS/m], is around 40 mils.
Your experience may more have related to 'fresh' water like boiling water
for tea where the less salt in the water the deeper the skin depth.

[meow...@care2.com]

On Sunday, September 28, 2014 3:46:22 PM UTC+1, Robert Macy wrote:

> On Sat, 27 Sep 2014 21:30:04 -0700, <dagmargoodboat@> wrote:
> >> ....snip....
> > I stand corrected. Thanks.
> >
> > Accordingly, the cornea intercepts only a fraction of the incident
> > microwave energy and will experience a lower temp rise than if it
> > absorbed all the microwave energy.
> >
> > That makes it even harder to understand how something you couldn't
> > feel on your skin could somehow cook your corneas.

> WAIT! first if you inject energy [heat rise] INTO something the
> distributed effect is that inside where something is getting hotter next
> to something getting even hotter, of course the internal temp rises! the

I think the question is whether its to any significant extent. Even if you got an exceptionally dodgy 1970s oven leaking 1w, the corneas can only absorb a tiny fraction of that watt, since they only opccupy a tiny percentage of the area around the oven. So rendering any temp rise so miniscule as to be totally dwarfed by normal air temp changes.

> outside will ALWAYS be cooler. Plus, as the water heats, evaporates, the
> energy can go in further, and so on.

> HOWEVER, there is still a decided skin effect in a water soaked something
> being heated in a microwave. The outside edges get most of the heat
> energy, but the 'captured' interior appears to heat more.

It does heat more. Not the centre, but an inch or so inside the surface.
Lets take the example of defrosting a slice of frozen desert. The outer edges are surrounded by warm air, the interior is surrounded by cold ice. Yet an inch in it heats as much as the surface. 2" in, less so.

> to 'see' skin
> depth in a microwave, scramble an egg, place in a shallow dish, and watch
> as the ring of cooked egg progresses from the outside to the inside.

That simply does not demonstrate skin depth. The rf in a nuke oven is deliberately bounced all round the place to get more even cooking, so your egg is getting hit from every which way. If you put a light bulb in a nuke and power it up, you'll see how the rf energy distribution has not a whole lot to do with the kind of side firing single source you'd need for your skin depth demo.


NT

[RobertMacy]

On Sun, 28 Sep 2014 10:29:14 -0700, <meow...@care2.com> wrote:

> On Sunday, September 28, 2014 3:46:22 PM UTC+1, Robert Macy wrote:

>> ...snip....

>> HOWEVER, there is still a decided skin effect in a water soaked
>> something
>> being heated in a microwave. The outside edges get most of the heat
>> energy, but the 'captured' interior appears to heat more.
>
> It does heat more. Not the centre, but an inch or so inside the surface.
> Lets take the example of defrosting a slice of frozen desert. The outer
> edges are surrounded by warm air, the interior is surrounded by cold
> ice. Yet an inch in it heats as much as the surface. 2" in, less so.
>

Bad example, ice is 'transparent to uWave. of course the energy will go in
a long way.

>> to 'see' skin
>> depth in a microwave, scramble an egg, place in a shallow dish, and
>> watch
>> as the ring of cooked egg progresses from the outside to the inside.
>
> That simply does not demonstrate skin depth. The rf in a nuke oven is
> deliberately bounced all round the place to get more even cooking, so
> your egg is getting hit from every which way. If you put a light bulb in
> a nuke and power it up, you'll see how the rf energy distribution has
> not a whole lot to do with the kind of side firing single source you'd
> need for your skin depth demo.
>
>
> NT

Again, was showing how the outside 'shields' the inside, [cooking first]
that is like skin effect.

Like a visual allegory of what is happening.

[meow...@care2.com]

Sure, only problem is it doesnt.

> that is like skin effect.
> Like a visual allegory of what is happening.

NT

[moha...@gmail.com]

On Monday, July 21, 2014 10:50:45 AM UTC-7, Tim Wescott wrote:

> On Mon, 21 Jul 2014 02:04:24 -0700, jrwalliker wrote:
>
> > On Monday, 25 November 1996 08:00:00 UTC, Thomas Pappano wrote:
> >
> >> Magnetrons are a specialized diode that operates in the influence of a
> >> magnetic field and usually have integral resonant circuitry that
> >> defines the frequency band they run in. They are used in pulsed
> >> applications such as pulse radar and also in continuous wave
> >> applications like microwave ovens.
> >
> > Every microwave oven I have looked at (with an antenna and diode
> > detector) is pulsed. I think each pulse lasts around 100us with a

> > repetition rate of 100Hz (in the UK) at full power. In low-power modes

> > the pulse repetition rate is reduced but the peak power is unchanged.
> >

> > The frequency is unstable, so as the turntable rotates with a slightly
> > asymmetric load the frequency drifts up and down (within the ISM band)
>

> Can we hand out awards for most years elapsed between question and
> answer? Nearly 18 years may not be a record, but it's pretty good, all
> in all.
>
> --
>
> Tim Wescott
> Wescott Design Services
> http://www.wescottdesign.com

Tim,

I was going to say what you exactly said here: these answers are very interesting, damn good even after 18 years, no that the laws of physics has or the principles of K&M has changed since then. But I found them quite interesting. Thanks! I am working on a design concept and possibly an engineering spec on a magnetronic system for some special purpose heating applications. Would you know of a good reference for multi -ega Watt (dielectric) heating?

Thanks, Ali

[Adrian Jansen]

My suspicious mind is wondering whether someone like Google is throwing
ancient threads into the newsgroups, either by accident, or design, just
to see what happens. I saw something similar on the aus.electronics
group recently too, where a query from 1996 about BWD oscilloscopes was
raised and discussed. Interesting that both that and this are from the
same year. Maybe related to the "Not Too Sure about Thunderbird" thread ?

--
Regards,

Adrian Jansen adrianjansen at internode dot on dot net
Note reply address is invalid, convert address above to machine form.

[Lasse Langwadt Christensen]

not related, the thunderbird thread was a screwed up server

the ancient threads is just people that stumble over a post on google and
reply without looking at the date

-Lasse