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Re: Microwave Oven at 2450 Mhz



MK and Luc,

This is one of those questions that shows up periodically on lists like
amsat-bb, Moon-Net, or microwave.  

It was thoroughly investigated by microwave hams back in the 1970's (esp.
by members of sbms http://www.ham-radio.com/sbms/).
Hope was that the high power cavity oscillators used in microwave ovens
(Magnetrons) could be stabilized and moved to normal 2.3 GHz ham
frequencies.  There was work on using LO injection frequency locking to
stabilize the normal wide-band signal and pull it in frequency.  Ovens use
HV supplies that do not produce a clean oscillation so that was worked on.
One experimenter discovered that 
back bombardment of the cathode produced noise modulation and found that
removing filament voltage after oscillation was started improve this.  In
the end it was decided that "mags" were just not the right tube for
narrow-band communication.

Klystrons, on the other hand, been used a lot in the past.  I used a 100mw
klystron in my first mw rig: 
http://www.qsl.net/al7eb/mw3456.htm
Today solid-state oscillators and amplifiers have made them obsolete at low
powers.  Microwavers generally chose TWT amplifiers for QRO power on mw
today, as they are becoming fairly common surplus as solid-state amps
replace them in commercial equipment.

A final issue is that the 500 to 1400w power levels put out by microwave
maggies is lethal!  Dangerous stuff!  The oven manufacturers go to lengths
to place safety interrupts on doors to avoid accidental exposure (and law
suits).

It is not too hard to develop 50w with solid-state and 100-150w with mw
triode tubes at 2.4 GHz today.

73's Ed - AL7EB
PS:  perhaps I will scan a photo with me holding a oven magnetron in the
1970's on my website.
NASA was working on a project using arrays of oven-magnetrons to beam solar
power from orbit, but scrapped it as too dangerous for aviation and birds
that might inadvertently fly thru the beam.  30% efficiency of power
transmission was achieved over several miles.

At 10:42 AM 2/20/2005 -0500, Luc Leblanc VE2DWE wrote:
>On 20 Feb 2005 at 6:38, M. K. Hess wrote:
>
>> I've often wondered if the Klystons & Magnetron tubes from old microwave
>> ovens are at all useful in constructing a 13cm transmitter. Any thoughts on
>> that?
>> 
>> N3EAQ
>> 73
>
>
>I remember some post on some Wifi BB where some report tests to boost 
>wireless routers signal using microwave components. Main problems 
>reported where:
>
>Instability, spurious harmonics, not filtration or isolation from 
>square waves.  In short it seems to be very hard to make these tubes 
>working as an amplifier on 2.4GHZ.
>
>
>
>
>"-"
>Luc Leblanc VE2DWE
>Coordonnateur AMSAT Quebec coordonnator
>AMSAT 33583
>www.qsl.net/ve2dwe 
>----
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