Op amps problem Gain Calculation

On Tue, 12 Dec 2017 03:49:55 -0000, rickman <gnuarm@gmail.com> wrote:

James Wilkinson Sword wrote on 12/11/2017 11:50 AM:
On Mon, 11 Dec 2017 04:07:43 -0000, Mary-Jane Rottencrotch
usenet@buttocks.local> wrote:

On 2007-01-19 12:13, Peter Fucker wrote:
Is it really true that turning on a microwave with nothing in it will
break it?

Derp.

It was a sensible question. This could be done by accident.

I interviewed with a place once that was doing something with testing
microwave ovens. They ran them all the time with nothing in them. I had
always read that you should not operate them with nothing to absorb the
energy and mentioned that. I got a strange look from the guy. Obviously
the energy that would be absorbed is within the limits of what the ovens
were designed to get rid of.
Click to expand...

It seems nothing happens, well no fire or explosion anyway. He never said if it still worked afterwards:
https://youtu.be/AsaW5xnOkCA

--
Exersize: the act of removing excess baggage
 
On 2017/12/12 6:14 AM, James Wilkinson Sword wrote:
On Tue, 12 Dec 2017 03:49:55 -0000, rickman <gnuarm@gmail.com> wrote:

James Wilkinson Sword wrote on 12/11/2017 11:50 AM:
On Mon, 11 Dec 2017 04:07:43 -0000, Mary-Jane Rottencrotch
usenet@buttocks.local> wrote:

On 2007-01-19 12:13, Peter Fucker wrote:
Is it really true that turning on a microwave with nothing in it will
break it?

Derp.

It was a sensible question.  This could be done by accident.

I interviewed with a place once that was doing something with testing
microwave ovens.  They ran them all the time with nothing in them.  I had
always read that you should not operate them with nothing to absorb the
energy and mentioned that.  I got a strange look from the guy.  Obviously
the energy that would be absorbed is within the limits of what the ovens
were designed to get rid of.

It seems nothing happens, well no fire or explosion anyway.  He never
said if it still worked afterwards:
https://youtu.be/AsaW5xnOkCA
Click to expand...

Why don't you simply put a load meter on the microwave and try running
it empty or with a cup of water. I expect that with no load the unit
will simply not draw as much current.

Do regular ovens 'care' if something is in them or not? Why should a
microwave?

John :-#(#
 
On Tue, 12 Dec 2017 16:12:51 -0000, John Robertson <spam@flippers.com> wrote:

On 2017/12/12 6:14 AM, James Wilkinson Sword wrote:
On Tue, 12 Dec 2017 03:49:55 -0000, rickman <gnuarm@gmail.com> wrote:

James Wilkinson Sword wrote on 12/11/2017 11:50 AM:
On Mon, 11 Dec 2017 04:07:43 -0000, Mary-Jane Rottencrotch
usenet@buttocks.local> wrote:

On 2007-01-19 12:13, Peter Fucker wrote:
Is it really true that turning on a microwave with nothing in it will
break it?

Derp.

It was a sensible question. This could be done by accident.

I interviewed with a place once that was doing something with testing
microwave ovens. They ran them all the time with nothing in them. I had
always read that you should not operate them with nothing to absorb the
energy and mentioned that. I got a strange look from the guy. Obviously
the energy that would be absorbed is within the limits of what the ovens
were designed to get rid of.

It seems nothing happens, well no fire or explosion anyway. He never
said if it still worked afterwards:
https://youtu.be/AsaW5xnOkCA


Why don't you simply put a load meter on the microwave and try running
it empty or with a cup of water. I expect that with no load the unit
will simply not draw as much current.

Do regular ovens 'care' if something is in them or not? Why should a
microwave?

John :-#(#
Click to expand...

A regular oven switches off the heater once the inside is at 200C or whatever you set it to.

A microwave oven works completely differently. 900W (or so) of microwave energy continuously enters the cavity and should be absorbed by the food. If it isn't, where does that microwave energy go?

--
The only substitute for good manners is fast reflexes.
 
On 2017/12/12 8:25 AM, James Wilkinson Sword wrote:
On Tue, 12 Dec 2017 16:12:51 -0000, John Robertson <spam@flippers.com
wrote:

On 2017/12/12 6:14 AM, James Wilkinson Sword wrote:
On Tue, 12 Dec 2017 03:49:55 -0000, rickman <gnuarm@gmail.com> wrote:

James Wilkinson Sword wrote on 12/11/2017 11:50 AM:
On Mon, 11 Dec 2017 04:07:43 -0000, Mary-Jane Rottencrotch
usenet@buttocks.local> wrote:

On 2007-01-19 12:13, Peter Fucker wrote:
Is it really true that turning on a microwave with nothing in it
will
break it?

Derp.

It was a sensible question.  This could be done by accident.

I interviewed with a place once that was doing something with testing
microwave ovens.  They ran them all the time with nothing in them.
I had
always read that you should not operate them with nothing to absorb the
energy and mentioned that.  I got a strange look from the guy.
Obviously
the energy that would be absorbed is within the limits of what the
ovens
were designed to get rid of.

It seems nothing happens, well no fire or explosion anyway.  He never
said if it still worked afterwards:
https://youtu.be/AsaW5xnOkCA


Why don't you simply put a load meter on the microwave and try running
it empty or with a cup of water. I expect that with no load the unit
will simply not draw as much current.

Do regular ovens 'care' if something is in them or not? Why should a
microwave?

John :-#(#

A regular oven switches off the heater once the inside is at 200C or
whatever you set it to.

A microwave oven works completely differently.  900W (or so) of
microwave energy continuously enters the cavity and should be absorbed
by the food.  If it isn't, where does that microwave energy go?
Click to expand...

When in doubt find a real answer:

http://products.geappliances.com/appliance/gea-support-search-content?contentId=17934

So, it seems microwaves will run up to five minutes when empty, but
after that will overheat various parts. And probably die.

Learn something every day!

John :-#)#
 
On Tue, 12 Dec 2017 16:43:05 -0000, John Robertson <spam@flippers.com> wrote:

On 2017/12/12 8:25 AM, James Wilkinson Sword wrote:
On Tue, 12 Dec 2017 16:12:51 -0000, John Robertson <spam@flippers.com
wrote:

On 2017/12/12 6:14 AM, James Wilkinson Sword wrote:
On Tue, 12 Dec 2017 03:49:55 -0000, rickman <gnuarm@gmail.com> wrote:

James Wilkinson Sword wrote on 12/11/2017 11:50 AM:
On Mon, 11 Dec 2017 04:07:43 -0000, Mary-Jane Rottencrotch
usenet@buttocks.local> wrote:

On 2007-01-19 12:13, Peter Fucker wrote:
Is it really true that turning on a microwave with nothing in it
will
break it?

Derp.

It was a sensible question. This could be done by accident.

I interviewed with a place once that was doing something with testing
microwave ovens. They ran them all the time with nothing in them.
I had
always read that you should not operate them with nothing to absorb the
energy and mentioned that. I got a strange look from the guy.
Obviously
the energy that would be absorbed is within the limits of what the
ovens
were designed to get rid of.

It seems nothing happens, well no fire or explosion anyway. He never
said if it still worked afterwards:
https://youtu.be/AsaW5xnOkCA


Why don't you simply put a load meter on the microwave and try running
it empty or with a cup of water. I expect that with no load the unit
will simply not draw as much current.

Do regular ovens 'care' if something is in them or not? Why should a
microwave?

John :-#(#

A regular oven switches off the heater once the inside is at 200C or
whatever you set it to.

A microwave oven works completely differently. 900W (or so) of
microwave energy continuously enters the cavity and should be absorbed
by the food. If it isn't, where does that microwave energy go?


When in doubt find a real answer:

http://products.geappliances.com/appliance/gea-support-search-content?contentId=17934

So, it seems microwaves will run up to five minutes when empty, but
after that will overheat various parts. And probably die.

Learn something every day!
Click to expand...

No, it says it will shut down. So clearly (that make anyway) has a thermal cutout and won't die.

--
If only women came with pull-down menus and on-line help.
 
On Tue, 12 Dec 2017 08:43:05 -0800, John Robertson <spam@flippers.com>
wrote:

>When in doubt find a real answer:

When in doubt, read about what manufacturers have done about the empty
oven problem.

Some patents:
"Oven protective device"
<https://patents.google.com/patent/US3281567A/>

"Electronic oven protection circuit"
<https://patents.google.com/patent/US3412227A/>

"System for sensing the presence of a load in an oven cavity of a
microwave cooking appliance"
<https://patents.google.com/patent/US6867402B1/>

There are probably other patents.

Basically, there is a directional coupler VSWR (voltage standing wave
ratio) detector or other scheme for detecting if the oven is empty,
which senses the high reflected power produces by an empty oven and
shuts it down.


Learn by Destroying(tm) or this should be tested by Mythbusters:

About 15 years ago, I was drawn into a discussion about what bad
things might happen if the oven were to run empty. Opinions varied
ranging from nothing to planetary destruction. I wasn't sure but
based on my RF experience, I guessed(tm) that it would be either a
huge increase in voltage across the magnetron, or a huge increase in
current through the magnetron. I placed my bet on some kind of
arcing, but didn't offer any specific location.

Three allegedly functional junk microwave ovens were purchased from
the local thrift shop for about $20/ea. When the owners of the store
found out what we were doing, she threw in three more ovens that had
various defects which made them unsellable, but were allegedly able to
heat water.

I don't have time right now for the whole story, so I'll just
summarize. Every oven acted or failed differently. As I vaguely
recall:
- One immediately shut itself off and would not restart until I
unplugged the power cord. My guess(tm) is I tripped an overcurrent
breaker.
- One turned itself off after about 30 seconds by blowing a fuse.
- One made a noise indicating the something had blown up inside, but
continued to run. After about 1 minute, there was another noise
followed by smell of burning electronics.
- One arced over some burned food on the waveguide window. I removed
the window and tried again. This time it arced intermittently inside
the waveguide near the window for about 15 minutes. There was a hint
that something electrical was burning inside, so we turned it off.
- One had some mechanical damage to the case, which caused some arcing
outside of the cooking area. Since that meant that we might have high
levels of RF leaking from the oven, we terminated the test early.

I have photos of the ovens and list of makers and models. I'm too
lazy/busy to find them right now. Suffice to say that there were no
fires, explosions, implosions, lightning bolts, ball lightning, toxic
discharges or devastating EMP. In most cases, the fuse or breaker
tripped, which is easily replaced or reset. Someone did an autopsy on
3 of the ovens and found one shorted magnetron and two blown Hi-V
diodes. The ovens that seemed to have burning electronic were not
inspected.

--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558
 
John Robertson wrote on 12/12/2017 11:12 AM:
On 2017/12/12 6:14 AM, James Wilkinson Sword wrote:
On Tue, 12 Dec 2017 03:49:55 -0000, rickman <gnuarm@gmail.com> wrote:

James Wilkinson Sword wrote on 12/11/2017 11:50 AM:
On Mon, 11 Dec 2017 04:07:43 -0000, Mary-Jane Rottencrotch
usenet@buttocks.local> wrote:

On 2007-01-19 12:13, Peter Fucker wrote:
Is it really true that turning on a microwave with nothing in it will
break it?

Derp.

It was a sensible question. This could be done by accident.

I interviewed with a place once that was doing something with testing
microwave ovens. They ran them all the time with nothing in them. I had
always read that you should not operate them with nothing to absorb the
energy and mentioned that. I got a strange look from the guy. Obviously
the energy that would be absorbed is within the limits of what the ovens
were designed to get rid of.

It seems nothing happens, well no fire or explosion anyway. He never said
if it still worked afterwards:
https://youtu.be/AsaW5xnOkCA


Why don't you simply put a load meter on the microwave and try running it
empty or with a cup of water. I expect that with no load the unit will
simply not draw as much current.
Click to expand...

I don't think a microwave works like a transformer. The energy is emitted
by the unit like an antenna regardless of whether there is something to
absorb it or not. The difference is with a radio antenna the energy is free
to leave the transmitter into free space. A microwave is in a sealed box.

Hmmm... maybe the waves do go back into the klystron and reduce the power
drawn. Then why would the makers have warned to not run them empty?


> Do regular ovens 'care' if something is in them or not? Why should a microwave?

Because they aren't the same?

--

Rick C

Viewed the eclipse at Wintercrest Farms,
on the centerline of totality since 1998
 
Jeff Liebermann wrote on 12/12/2017 2:26 PM:
Three allegedly functional junk microwave ovens were purchased from
the local thrift shop for about $20/ea. When the owners of the store
found out what we were doing, she threw in three more ovens that had
various defects which made them unsellable, but were allegedly able to
heat water.

I don't have time right now for the whole story, so I'll just
summarize. Every oven acted or failed differently.
Click to expand...

Jeff, you are a trip!

--

Rick C

Viewed the eclipse at Wintercrest Farms,
on the centerline of totality since 1998
 
On Tue, 12 Dec 2017 22:00:53 -0000, rickman <gnuarm@gmail.com> wrote:

John Robertson wrote on 12/12/2017 11:12 AM:
On 2017/12/12 6:14 AM, James Wilkinson Sword wrote:
On Tue, 12 Dec 2017 03:49:55 -0000, rickman <gnuarm@gmail.com> wrote:

James Wilkinson Sword wrote on 12/11/2017 11:50 AM:
On Mon, 11 Dec 2017 04:07:43 -0000, Mary-Jane Rottencrotch
usenet@buttocks.local> wrote:

On 2007-01-19 12:13, Peter Fucker wrote:
Is it really true that turning on a microwave with nothing in it will
break it?

Derp.

It was a sensible question. This could be done by accident.

I interviewed with a place once that was doing something with testing
microwave ovens. They ran them all the time with nothing in them. I had
always read that you should not operate them with nothing to absorb the
energy and mentioned that. I got a strange look from the guy. Obviously
the energy that would be absorbed is within the limits of what the ovens
were designed to get rid of.

It seems nothing happens, well no fire or explosion anyway. He never said
if it still worked afterwards:
https://youtu.be/AsaW5xnOkCA


Why don't you simply put a load meter on the microwave and try running it
empty or with a cup of water. I expect that with no load the unit will
simply not draw as much current.

I don't think a microwave works like a transformer. The energy is emitted
by the unit like an antenna regardless of whether there is something to
absorb it or not. The difference is with a radio antenna the energy is free
to leave the transmitter into free space. A microwave is in a sealed box.

Hmmm... maybe the waves do go back into the klystron and reduce the power
drawn. Then why would the makers have warned to not run them empty?
Click to expand...

Perhaps the power going back into the klystron causes heating? Perhaps the power goes into other parts and causes damage?

--
For this race I'm going to be using "beati dogu". Japanese for the ancient art of driving a sports car round a track faster than a greyhound. -- Richard Hammond
 
James Wilkinson Sword wrote:


Perhaps the power going back into the klystron causes heating? Perhaps
the power goes into other parts and causes damage?
Click to expand...
Microwave ovens use magnetrons, not klystrons. When power is applied to the
magnetron, it is pretty independent of the RF load, you apply a couple
thousand Volts minus to the cathode, and the anode is grounded. But, due to
the magnetic field, the electrons spiral outward instead of just heading
straight outward radially to the anode. Passing the resonant cavities
repeatedly during that spiral path builds the RF resonance.

The oven chamber develops standing waves. If there is nothing to absorb the
RF, it is reflected back into the magnetron, and the anode runs hotter. I
think the thermal switch on the anode is more to cover the condition where
the fan motor has seized up than no food in the oven, but may handle both to
some extent.

Jon
 
On 2017/12/12 2:04 PM, rickman wrote:
Jeff Liebermann wrote on 12/12/2017 2:26 PM:

Three allegedly functional junk microwave ovens were purchased from
the local thrift shop for about $20/ea.  When the owners of the store
found out what we were doing, she threw in three more ovens that had
various defects which made them unsellable, but were allegedly able to
heat water.

I don't have time right now for the whole story, so I'll just
summarize.  Every oven acted or failed differently.

Jeff, you are a trip!
Click to expand...

He is having too much fun - Ban Jeff!

(thanks, Jeff!!)

John :-#)#

--
(Please post followups or tech inquiries to the USENET newsgroup)
John's Jukes Ltd.
MOVED to #7 - 3979 Marine Way, Burnaby, BC, Canada V5J 5E3
(604)872-5757 (Pinballs, Jukes, Video Games)
www.flippers.com
"Old pinballers never die, they just flip out."
 
"Mary-Jane Rottencrotch" <usenet@buttocks.local> wrote in message
news:Nu-dnccoR7ENmbPHnZ2dnUU7-XWdnZ2d@supernews.com...
On 2007-01-19 12:13, Peter Fucker wrote:
Is it really true that turning on a microwave with nothing in it will
break it?

Derp.
Click to expand...

I've never had one blow up because of that, but its best avoided.

There may be am increased risk of arcing the dielectric window that covers
the end of the waveguide.

So far - I've yet to actually buy a microwave, I've done well out of simply
removing a damaged dielectric window and carrying on. Carbonised food
spatter is a far more common cause, but I wouldn't leave an empty microwave
running longer than it took to realise my mistake.
 
"Jon Elson" <jmelson@wustl.edu> wrote in message
news:1tWdnRf4zMTEya3HnZ2dnUU7-RPNnZ2d@giganews.com...
James Wilkinson Sword wrote:


Perhaps the power going back into the klystron causes heating? Perhaps
the power goes into other parts and causes damage?

Microwave ovens use magnetrons, not klystrons. When power is applied to
the
magnetron, it is pretty independent of the RF load, you apply a couple
thousand Volts minus to the cathode, and the anode is grounded. But, due
to
the magnetic field, the electrons spiral outward instead of just heading
straight outward radially to the anode. Passing the resonant cavities
repeatedly during that spiral path builds the RF resonance.

The oven chamber develops standing waves. If there is nothing to absorb
the
RF, it is reflected back into the magnetron, and the anode runs hotter. I
think the thermal switch on the anode is more to cover the condition where
the fan motor has seized up than no food in the oven, but may handle both
to
some extent.
Click to expand...

Reflected waves can augment or cancel - or anywhere in between.

AFAIK: the extremes are flashover in the magnetron or excessive current
draw. I doesn't take much excessive current draw to cause shorted turns in
the mains transformer.
 
rickman wrote:
James Wilkinson Sword wrote on 12/11/2017 11:50 AM:
On Mon, 11 Dec 2017 04:07:43 -0000, Mary-Jane Rottencrotch
usenet@buttocks.local> wrote:

On 2007-01-19 12:13, Peter Fucker wrote:
Is it really true that turning on a microwave with nothing in it will
break it?

Derp.

It was a sensible question. This could be done by accident.

I interviewed with a place once that was doing something with testing
microwave ovens. They ran them all the time with nothing in them. I
had always read that you should not operate them with nothing to absorb
the energy and mentioned that. I got a strange look from the guy.
Obviously the energy that would be absorbed is within the limits of what
the ovens were designed to get rid of.

STUPID!
Click to expand...

Microwave ovens *generate* (microwave) energy and cannot "get rid" of
any of that.

It boils down to how much of a load mis-match (SWR) can the magnetron
("maggie") tolerate.

Nothing will "break", but the maggie may burn out.
 
James Wilkinson Sword wrote:
On Tue, 12 Dec 2017 03:49:55 -0000, rickman <gnuarm@gmail.com> wrote:

James Wilkinson Sword wrote on 12/11/2017 11:50 AM:
On Mon, 11 Dec 2017 04:07:43 -0000, Mary-Jane Rottencrotch
usenet@buttocks.local> wrote:

On 2007-01-19 12:13, Peter Fucker wrote:
Is it really true that turning on a microwave with nothing in it will
break it?

Derp.

It was a sensible question. This could be done by accident.

I interviewed with a place once that was doing something with testing
microwave ovens. They ran them all the time with nothing in them. I had
always read that you should not operate them with nothing to absorb the
energy and mentioned that. I got a strange look from the guy. Obviously
the energy that would be absorbed is within the limits of what the ovens
were designed to get rid of.

You'd think there would be something that absorbs microwaves that miss
the food. And you'd think such a thing would have a thermal cutout.
Anybody want to try it?
Click to expand...
IDIOT!
ain't nuttin that "absorbs" the energy.
Ask how the maggie works with highly mis-matched loads (hi SWR).
 
rickman wrote:
Jeff Liebermann wrote on 12/12/2017 2:26 PM:

Three allegedly functional junk microwave ovens were purchased from
the local thrift shop for about $20/ea. When the owners of the store
found out what we were doing, she threw in three more ovens that had
various defects which made them unsellable, but were allegedly able to
heat water.

I don't have time right now for the whole story, so I'll just
summarize. Every oven acted or failed differently.

Jeff, you are a trip!
Click to expand...
I live in an apartment complex, and a lot of microwave ovens have
been thrown away; and most of them were perfectly OK after they were
cleaned up.
Same pattern with vacuum cleaners.
A number of people are pigs.
 
On Thu, 28 Dec 2017 03:56:51 -0000, Robert Baer <robertbaer@localnet.com> wrote:

rickman wrote:
James Wilkinson Sword wrote on 12/11/2017 11:50 AM:
On Mon, 11 Dec 2017 04:07:43 -0000, Mary-Jane Rottencrotch
usenet@buttocks.local> wrote:

On 2007-01-19 12:13, Peter Fucker wrote:
Is it really true that turning on a microwave with nothing in it will
break it?

Derp.

It was a sensible question. This could be done by accident.

I interviewed with a place once that was doing something with testing
microwave ovens. They ran them all the time with nothing in them. I
had always read that you should not operate them with nothing to absorb
the energy and mentioned that. I got a strange look from the guy.
Obviously the energy that would be absorbed is within the limits of what
the ovens were designed to get rid of.

STUPID!

Microwave ovens *generate* (microwave) energy and cannot "get rid" of
any of that.

It boils down to how much of a load mis-match (SWR) can the magnetron
("maggie") tolerate.

Nothing will "break", but the maggie may burn out.
Click to expand...

There is a block to absorb the energy that comes back. It should have a thermal cutout on it.

--
Sweet dreams are made of cheese, who am I to diss a Brie? I cheddar the world and the feta cheese, everybody's looking for Stilton.
 
On Thu, 28 Dec 2017 03:59:42 -0000, Robert Baer <robertbaer@localnet.com> wrote:

James Wilkinson Sword wrote:
On Tue, 12 Dec 2017 03:49:55 -0000, rickman <gnuarm@gmail.com> wrote:

James Wilkinson Sword wrote on 12/11/2017 11:50 AM:
On Mon, 11 Dec 2017 04:07:43 -0000, Mary-Jane Rottencrotch
usenet@buttocks.local> wrote:

On 2007-01-19 12:13, Peter Fucker wrote:
Is it really true that turning on a microwave with nothing in it will
break it?

Derp.

It was a sensible question. This could be done by accident.

I interviewed with a place once that was doing something with testing
microwave ovens. They ran them all the time with nothing in them. I had
always read that you should not operate them with nothing to absorb the
energy and mentioned that. I got a strange look from the guy. Obviously
the energy that would be absorbed is within the limits of what the ovens
were designed to get rid of.

You'd think there would be something that absorbs microwaves that miss
the food. And you'd think such a thing would have a thermal cutout.
Anybody want to try it?

IDIOT!
ain't nuttin that "absorbs" the energy.
Ask how the maggie works with highly mis-matched loads (hi SWR).
Click to expand...

I went for an interview in a place that designed industrial strength magnetron. There IS a block to absorb energy. A microwave oven without one is VERY badly designed.

--
If only women came with pull-down menus and on-line help.
 
On Thu, 28 Dec 2017 04:03:22 -0000, Robert Baer <robertbaer@localnet.com> wrote:

rickman wrote:
Jeff Liebermann wrote on 12/12/2017 2:26 PM:

Three allegedly functional junk microwave ovens were purchased from
the local thrift shop for about $20/ea. When the owners of the store
found out what we were doing, she threw in three more ovens that had
various defects which made them unsellable, but were allegedly able to
heat water.

I don't have time right now for the whole story, so I'll just
summarize. Every oven acted or failed differently.

Jeff, you are a trip!

I live in an apartment complex, and a lot of microwave ovens have
been thrown away; and most of them were perfectly OK after they were
cleaned up.
Same pattern with vacuum cleaners.
A number of people are pigs.
Click to expand...

I got four Dysons off freecycle (because they're infamous for falling to bits). Put all the faulty parts into one, then the other three work :)

--
In the first few days of the Olympics the Rumanians took gold, silver, bronze, copper, lead and anything else they could get their bloody hands on.
 
James Wilkinson Sword wrote:
On Thu, 28 Dec 2017 03:59:42 -0000, Robert Baer
robertbaer@localnet.com> wrote:

James Wilkinson Sword wrote:
On Tue, 12 Dec 2017 03:49:55 -0000, rickman <gnuarm@gmail.com> wrote:

James Wilkinson Sword wrote on 12/11/2017 11:50 AM:
On Mon, 11 Dec 2017 04:07:43 -0000, Mary-Jane Rottencrotch
usenet@buttocks.local> wrote:

On 2007-01-19 12:13, Peter Fucker wrote:
Is it really true that turning on a microwave with nothing in it
will
break it?

Derp.

It was a sensible question. This could be done by accident.

I interviewed with a place once that was doing something with testing
microwave ovens. They ran them all the time with nothing in them.
I had
always read that you should not operate them with nothing to absorb the
energy and mentioned that. I got a strange look from the guy.
Obviously
the energy that would be absorbed is within the limits of what the
ovens
were designed to get rid of.

You'd think there would be something that absorbs microwaves that miss
the food. And you'd think such a thing would have a thermal cutout.
Anybody want to try it?

IDIOT!
ain't nuttin that "absorbs" the energy.
Ask how the maggie works with highly mis-matched loads (hi SWR).

I went for an interview in a place that designed industrial strength
magnetron. There IS a block to absorb energy. A microwave oven without
one is VERY badly designed.
Click to expand...
Rule of thumb or any commercial (= = volume) item is: for every fifty
cent cost to make, selling price must go up by five dollars (cars, toys,
etc).
Industrial grade magge-powered ovens cost a lot more than the over
the counter el-cheapos that the great unwashed buy.
 
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