Me:

Oh really, so if part of the waveguide is made resonant at 800 MHz and I
am striking it with a "1KW hammer" it will not "ring" at all? Funny,
but that runs against all I have seen here in the real world...

John

"Me" wrote in message
...
In article ,
"John Smith" wrote:

I would think a 1KW or greater magnetron run off a non-filtered and
particularly dirty, but rectified dc supply (you could even feed a
ramp
or triangle dc power wave to the magnetron to cause frequency sweep)
and
into a sloppy waveguide exhibiting multiple resonant frequencies
would
knock out all cell phone and wireless communications on shf+ freqs
for
blocks if not miles... you would probably start jamming the cell
towers
for miles around and have every "pirate transmitter" hunter in
America
on your tail... in a large city/metro area you would cause havoc to
break out--this WOULD BE ONE SERIOUS OFFENSE!!! If caught, you would
learn to call prison your home!

And Bruce, in the cell next to you, would fall in love with you!

Not to mention the danger of exposure to the freqs in question--this
would be best left alone...

John

Bull****, a 2.4 Ghz Magnitron would NOT cause any problems for any
800
Mhz or even any 1.8 Ghz cellphone system no matter how bad the
powersupply was filtered. This just doesn't COMPUTE, even in another
world, lifetime, or dimension.


Me

'Course, there is a method of running a STABLE SOURCE , relatively
low power , coupled to a microwave oscillator source, and locking
it to a the frequency of the stable source- tho don't know if it works
with Magnetrons-- does with klystrons, and Tuned Grid-Tuned Plate oscs,
tho! Jim NN7K

Me wrote:
In article ,
"John Smith" wrote:


I would think a 1KW or greater magnetron run off a non-filtered and
particularly dirty, but rectified dc supply (you could even feed a ramp
or triangle dc power wave to the magnetron to cause frequency sweep) and
into a sloppy waveguide exhibiting multiple resonant frequencies would
knock out all cell phone and wireless communications on shf+ freqs for
blocks if not miles... you would probably start jamming the cell towers
for miles around and have every "pirate transmitter" hunter in America
on your tail... in a large city/metro area you would cause havoc to
break out--this WOULD BE ONE SERIOUS OFFENSE!!! If caught, you would
learn to call prison your home!

And Bruce, in the cell next to you, would fall in love with you!

Not to mention the danger of exposure to the freqs in question--this
would be best left alone...

John

"John Smith" wrote in message
...
Me:

Oh really, so if part of the waveguide is made resonant at 800 MHz and I
am striking it with a "1KW hammer" it will not "ring" at all? Funny, but
that runs against all I have seen here in the real world...

John

A waveguide can be considered a very wide bandpass filter. Any frequency
coupled to the waveguide, within its pass-band, will appear at the output of
the waveguide. There will be no spurious signals attributed to the
waveguide. As mentioned previously; measurements I have made on microwave
oven magnetrons indicate an extremely wideband, highly unstable signal,
covering hundreds of MHz either side of the nominal 2.45 GHz. The potential
for interference to other services, particularly the 2.4 GHz ISM band, and
to a lesser extent, the 1.9 GHz cell frequencies, is fairly high. It is
doubtful that any significant energy will be present at 800 MHz.

The relative spectral purity of the magnetron measured in
http://www-personal.engin.umich.edu/...laes_tps04.pdf probably
used a laboratory grade 4kV power supply. Note, however, that significant
120 MHz sidebands (and harmonics) are present.

Frank

.... if I was to attempt to jam that broad of range of freqs, I would
couple it to a waveguide which exhibited resonance on that whole
spectrum (feed the center of circular guide/"modified horn" with
shortest point to edge of circle resonant at 2.4 ghz resonant, longest
point to edge of circle resonant at 800 mhz) , feeding the magnetron a
ramp or triangle dc voltage/current of 1 mhz freq--is going to generate
harmonics until the cows come home... I would feel like Dr. Frankenstein
when the neighbors showed up on my door step with their pitchforks and
scythes!!!

Warmest regards,
John

"Frank" wrote in message
newsbNre.54658$on1.13081@clgrps13...

"John Smith" wrote in message
...
Me:

Oh really, so if part of the waveguide is made resonant at 800 MHz
and I am striking it with a "1KW hammer" it will not "ring" at all?
Funny, but that runs against all I have seen here in the real
world...

John

A waveguide can be considered a very wide bandpass filter. Any
frequency coupled to the waveguide, within its pass-band, will appear
at the output of the waveguide. There will be no spurious signals
attributed to the waveguide. As mentioned previously; measurements I
have made on microwave oven magnetrons indicate an extremely wideband,
highly unstable signal, covering hundreds of MHz either side of the
nominal 2.45 GHz. The potential for interference to other services,
particularly the 2.4 GHz ISM band, and to a lesser extent, the 1.9 GHz
cell frequencies, is fairly high. It is doubtful that any significant
energy will be present at 800 MHz.

The relative spectral purity of the magnetron measured in
http://www-personal.engin.umich.edu/...laes_tps04.pdf
probably used a laboratory grade 4kV power supply. Note, however,
that significant 120 MHz sidebands (and harmonics) are present.

Frank

"John Smith" wrote in message
...
... if I was to attempt to jam that broad of range of freqs, I would
couple it to a waveguide which exhibited resonance on that whole spectrum
(feed the center of circular guide/"modified horn" with shortest point to
edge of circle resonant at 2.4 ghz resonant, longest point to edge of
circle resonant at 800 mhz) , feeding the magnetron a ramp or triangle dc
voltage/current of 1 mhz freq--is going to generate harmonics until the
cows come home... I would feel like Dr. Frankenstein when the neighbors
showed up on my door step with their pitchforks and scythes!!!

Warmest regards,
John

Not sure how the magnetron would respond to a ramp, but at some amplitude
the magnetron would cease oscillations. The fact is that the harmonic decay
of a sawtooth waveform is slightly higher than a rectangular pulse. A worst
case analysis would involve a rectangular pulse with a finite rise/fall
time. If for example the magnetron were pulsed with a square wave, 50% duty
cycle, at 1 MHz, with a rise time of 10nS, the 1,600 th harmonic (i.e.
lower sideband at 800 MHz) amplitude is about -50 dBC. This result is
obtained from the solution of the products of two Sa(x) functions involving
the rise time, period, and pulse width of a symmetrical trapezoidal
waveform. If you have a burning desire to know, I can vary the parameters
of rise time, pulse width, etc. to see how the spectral shape changes.

These sidebands, in the vicinity of 800 MHz, are therfore of significant
amplitude. I am, however, fairly certain that 800 MHz is below the
waveguide cut-off frequency. I will try and measure the dimensions of a
typical oven waveguide to determine its cut-off frequency. The other factor
is the Q of the magnetron cavities how would this effect the banwidth of the
spectrum? Since the magnetron is coupled to the waveguide from a probe in
one of its cavities, I would think that the higher sidebands would be
significantly reduced. Possibly you have made measurements on such a
system.

The math, at least, does indicate the potential of building a very wide band
jammer -- probably not a good idea!

73,

Frank

.... no need, I have seen the results of such devices in practical
operation...

I do a class at the jr. college here, have 3 sons in the computer field,
my garage is a clubhouse/wireless point/computer lab...

.... lot of cs/electronics majors... they have fired up such devices
before I said, "Not here!!!"

Really got ****ed when it jammed my "late night talk radio" which I fall
asleep to...

Warmest regards,
John

"Frank" wrote in message
news:37_re.49668$wr.42366@clgrps12...
"John Smith" wrote in message
...
... if I was to attempt to jam that broad of range of freqs, I would
couple it to a waveguide which exhibited resonance on that whole
spectrum (feed the center of circular guide/"modified horn" with
shortest point to edge of circle resonant at 2.4 ghz resonant,
longest point to edge of circle resonant at 800 mhz) , feeding the
magnetron a ramp or triangle dc voltage/current of 1 mhz freq--is
going to generate harmonics until the cows come home... I would feel
like Dr. Frankenstein when the neighbors showed up on my door step
with their pitchforks and scythes!!!

Warmest regards,
John

Not sure how the magnetron would respond to a ramp, but at some
amplitude the magnetron would cease oscillations. The fact is that
the harmonic decay of a sawtooth waveform is slightly higher than a
rectangular pulse. A worst case analysis would involve a rectangular
pulse with a finite rise/fall time. If for example the magnetron were
pulsed with a square wave, 50% duty cycle, at 1 MHz, with a rise time
of 10nS, the 1,600 th harmonic (i.e. lower sideband at 800 MHz)
amplitude is about -50 dBC. This result is obtained from the solution
of the products of two Sa(x) functions involving the rise time,
period, and pulse width of a symmetrical trapezoidal waveform. If you
have a burning desire to know, I can vary the parameters of rise time,
pulse width, etc. to see how the spectral shape changes.

These sidebands, in the vicinity of 800 MHz, are therfore of
significant amplitude. I am, however, fairly certain that 800 MHz is
below the waveguide cut-off frequency. I will try and measure the
dimensions of a typical oven waveguide to determine its cut-off
frequency. The other factor is the Q of the magnetron cavities how
would this effect the banwidth of the spectrum? Since the magnetron
is coupled to the waveguide from a probe in one of its cavities, I
would think that the higher sidebands would be significantly reduced.
Possibly you have made measurements on such a system.

The math, at least, does indicate the potential of building a very
wide band jammer -- probably not a good idea!

73,

Frank

"John Smith" wrote in message
news
... no need, I have seen the results of such devices in practical
operation...

I do a class at the jr. college here, have 3 sons in the computer field,
my garage is a clubhouse/wireless point/computer lab...

... lot of cs/electronics majors... they have fired up such devices before
I said, "Not here!!!"

Really got ****ed when it jammed my "late night talk radio" which I fall
asleep to...

Warmest regards,
John

When people try to say you are talking garbage it sparks my curiosity, and
have to see for myself. I should have realized that Sa(x) almost goes on
forever. Even at 100 GHz from the carrier the sidebands are about -85 dBc.
Other factors will probably suppress these very high order sidebands, but
still interesting to crunch numbers. Now I have an overwhelming desire to
build a -4000 V pulse generator, just to see how close it comes to theory.

73,

Frank

Frank:

Lol, it is catching huh?

Almost without doubt, what was tearing up my am radio was the signal
being fed on the B+ rail (~1Mhz run by a "chopped" supply--and most
likely leaking some signal onto the house mains--I am guilty of not
making those suspicions clear)... however, their intent was to jam
wireless wans/lans--from what I heard--they were/are more than
successful...

I know there was great experimentation here in trying to get a microwave
magnetron "rock stable"--when that failed it lead to the "other"
experimentation...

Just in case there is something to this--be careful when and where you
operate it...I think it just might surprise you...

Warmest regards,
John

"Frank" wrote in message
news:Rx%re.49680$wr.38116@clgrps12...

"John Smith" wrote in message
news
... no need, I have seen the results of such devices in practical
operation...

I do a class at the jr. college here, have 3 sons in the computer
field, my garage is a clubhouse/wireless point/computer lab...

... lot of cs/electronics majors... they have fired up such devices
before I said, "Not here!!!"

Really got ****ed when it jammed my "late night talk radio" which I
fall asleep to...

Warmest regards,
John

When people try to say you are talking garbage it sparks my curiosity,
and have to see for myself. I should have realized that Sa(x) almost
goes on forever. Even at 100 GHz from the carrier the sidebands are
about -85 dBc. Other factors will probably suppress these very high
order sidebands, but still interesting to crunch numbers. Now I have
an overwhelming desire to build a -4000 V pulse generator, just to see
how close it comes to theory.

73,

Frank

"John Smith" wrote in message
...
Frank:

Lol, it is catching huh?

Almost without doubt, what was tearing up my am radio was the signal being
fed on the B+ rail (~1Mhz run by a "chopped" supply--and most likely
leaking some signal onto the house mains--I am guilty of not making those
suspicions clear)... however, their intent was to jam wireless
wans/lans--from what I heard--they were/are more than successful...

I know there was great experimentation here in trying to get a microwave
magnetron "rock stable"--when that failed it lead to the "other"
experimentation...

Just in case there is something to this--be careful when and where you
operate it...I think it just might surprise you...

Warmest regards,
John

When the microwave oven is running it interferes with my 200 kHz (conducted
over house wiring) intercom system (Rat Shack). I suspected that it was
noise from the power supply, and not the actual magnetron. I am still
inclined to believe that the selectivity of the magnetron cavities will
limit the modulated spectrum, not to mention the waveguide cut-off
frequency. If I get a chance I will look more carefully at the RF output
on a spectrum analyzer.

As for magnetron frequency stability and phase noise performance, I remember
COHO/STALO MTI RADAR, and thought that the magnetron was stabilized. This
is not true, as explained in http://www.alphalpha.org/radar/coho_e.html

The only way I can conceive of stabilizing is by the use of a tunable
magnetron and AFC system. Then there is also the possibility of injection
locking.

73,

Frank

Reading the responses, some valid, some not*, I guess the best
thing to try is:

o illuminate a surplus TVRO 12 ft dish with the magnetron
- collect and focus side lobes
- 36+ dbi gain
o use a regulated power supply the decrease the bandwidth
o use some form of bandpass filtering such as cavity resonators
o point the thing at the moon and listen for echos
o experiment using it as a ground mapping radar

I vaguely recall seeing something in a late 80's (?) magazine, may
be 73 or CQ VHF, that built a digital data link from a pair of 2 mbit
PC network cards and a magnetron.

* FYI:
o GSM cell phone bands = 850/1900 MHz for the Americas,
900/1850 MHz outside the Americas, not 2.4 GHz.
o microwave ovens with the door closed already interfere with
most 2.4 GHz ISM band FCC Part 15 devices in close proximity