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

"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

'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

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

"Anchor" wrote in message
news
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

The problem with the spectral width, and stability, of the magnetron limits
is usefulness for low signals. As mentioned before, see
http://www-personal.engin.umich.edu/...laes_tps04.pdf

Now I know what you are doing you might consider a "COHO/STALO" system, as
used in MTI RADARs, see http://www.alphalpha.org/radar/coho_e.html With
COHO/STALO, you could probably reduce the BW to near 1 Hz with digital
filtering.

You may also consider applying the free-space RADAR equation, to determine
the feasibility. With a nominal ERP of 4 MW you may be successful without
using COHO/STALO. Try pulsing the magnetron with a very low PRF, and use an
"A" scan monitor.

Regards,

Frank

Frank,

Thanks for the advise.

Obviously if it was trivial to modify magnetrons for communications in the
13 cm S band, there would be a lot of high power activity on that band and
fewer dead microwave ovens in landfill sites.

Surely a near KW of radio energy can be used for more than re-warming
left-overs. Maybe not.

Thanks for the advise.

Obviously if it was trivial to modify magnetrons for communications in the
13 cm S band, there would be a lot of high power activity on that band and
fewer dead microwave ovens in landfill sites.

Surely a near KW of radio energy can be used for more than re-warming
left-overs. Maybe not.

No problem, glad to help. It still might be interesting to plug in the
parameters to the free space radar equation, considering receiver noise
figure, and signal BW, etc.. I am sure there is data available on the
reflectivity of the Lunar surface. Of course COHO/STALO will only work if
you are receiving your own signal, so not much use if you are attempting to
work others.

As I suspected, some work has been done on the injection locking of
magnetrons; as in
http://www.lancs.ac.uk/cockcroft-ins...ul04/tahir.pdf
This presentation recommends an injection signal of 2% power, or 20 W in the
case of a 1 kW magnetron. I have no experience on solid state amplifiers at
such a frequency (except for TWTs), but the construction of a single loop
synthesizer using ,a National Semiconductor chip, and a Z-Communications (or
Mini-Circuits etc.) SMT oscillator is trivial. There are lots of eval.
boards available for a nominal cost. I think Z-comm. has one, but have not
priced it recently. I guess such projects are a bit impractical unless you
have a good spectrum analyzer

73,

Frank

Found the following interesting site: http://www.df9cy.de/pathloss.htm
There is a downloadable spread sheet concerning moon-bounce path loss. I
have not verified the accuracy of the spread sheet, but it looks reasonable:

From the spread sheet, if you plug in the following parameters:

Power 1 kW;
BW 3 MHz;
Antenna gain 35 dB;
Frequency 2.4 GHz
and many more, such as noise figure, etc.

The received signal will be 40 dB below the noise.

Reducing the bandwidth to 100 Hz the signal will be about 4 dB above the
noise
-- as 10*log(BW1/BW2) will confirm.

Reduction in bandwidth to between 1 and 10 Hz would seem to be desirable.
Stability required is about 0.0004 ppm, not to mention degradation due to
TCXO 1/f noise.


Frank

One consideration is that Magnetrons are NOT designed, normally for ccs
service-- they are designed for "PULSE" service, even the ovens- (duty
cycle of MUCH less then even .5) and, pulse transmissions arn't looked
favorably on many of the microwave bands any more.


Anchor wrote:
Frank,

Thanks for the advise.

Obviously if it was trivial to modify magnetrons for communications in the
13 cm S band, there would be a lot of high power activity on that band and
fewer dead microwave ovens in landfill sites.

Surely a near KW of radio energy can be used for more than re-warming
left-overs. Maybe not.