"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

In article ,
Anchor wrote:

* FYI:

o microwave ovens with the door closed already interfere with
most 2.4 GHz ISM band FCC Part 15 devices in close proximity

Agreed, and it's not too surprising. The FCC doesn't regulate
microwave oven leakage, and the FDA's standard limits leakage for an
installed microwave oven to 5 milliwatts per cm^2 at a distance of 5
cm from the surface. I've read that a fairly high percentage of older
microwave ovens leak more than the standard would allow.

That level could add up pretty quickly... a watt or more of leakage
from an older microwave oven would not surprise me very much. A
15-milliwatt Part 15 device can't compete.

--
Dave Platt AE6EO
Hosting the Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!

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.

Here is an excellent and practical discussion of rough design and
practical use of can antennas, make sure to follow the link on the
bottom of the page...
http://www.turnpoint.net/wireless/an...coffeecan.html

John

"Anchor" wrote in message
news
Any suggestions on how to build a 2.4 GHz CW transmitter with a
microwave
oven magnetron and a 2.4 GHz "pringle" or coffee can style antenna?

There are tons of "pringle" or coffee can antennas or similar on the
web.
For example: http://flakey.info/antenna/waveguide or
http://www.turnpoint.net/wireless/an...coffeecan.html

I suppose one need only insert the magnetron antenna into the coffee
can
where one would normally mount the N-connector feed point.

A labeled diagram of a microwave magnetron can be found at:
http://www.gallawa.com/microtech/mag_test.html

I suppose the metal coffee can has superior micro shielding properties
relative to the aluminumized cardboard pringle can.

Would I be better off with plumbing copper drain pipe from the stray
RF
exposure perspective?

Since microwave magnetron use a half wave power supply, can I use two
magnetrons in the same coffee can powered from a single AC HV
transformer
with a pair of HV rectifiers to feed alternate cycles to the
magnetrons?

Greg, VE0ACR

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.

"Jim - NN7K" wrote in message
m...
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.

Sorry if I am repeating stuff that you may have seen before, but I have
noticed things that do not seem to add up. For example the paper at:
http://www-personal.engin.umich.edu/...aes_tps04.pdf;
Shows the CW output of the magnetron spectrum as -10 dBm. Since for the
output is monitored via a 30 dB coupler, and a 30 dB attenuator I would have
expected the amplitude to be 0 dBm. It is hard to imagine such testing
being done with a grossly overheated magnetron. Having observed the output
of a microwave oven on a spectrum analyzer, it did appear to be pulsed,
although the spectrum was more characteristic of a frequency hopping (or
swept) signal.

Frank