Visit Thanks for visiting Thanks for visiting the RF Cafe Archives Thank you for visiting RF Cafe Thank you for visiting the RF Cafe Archives!

uwave antenna question: ways to emit 2.45GHz for heat - RF Cafe Forums

The original RF Cafe Forums were shut down in late 2012 due to maintenance issues - primarily having to spend time purging garbage posts from the board. At some point I might start the RF Cafe Forums again if the phpBB software gets better at filtering spam.

Below are the old forum threads, including responses to the original posts.

-- Amateur Radio
-- Anecdotes, Gripes & Humor
-- Antennas
-- CAE, CAD, & Software
-- Circuits & Components
-- Employment & Interviews
-- Miscellany
-- Swap Shop
-- Systems
-- Test & Measurement
-- Webmaster

 Post subject: uwave antenna question: ways to emit 2.45GHz for heat
Posted: Mon Feb 07, 2005 2:14 am 
as a novice to RF, I am confused about antenna behavior and practical differences among types. There is a waveguide to a feedhorn, there is waveguide to coax to something... dipole or the like, heard about notch antenna whatever that is, transmission lines and even dishes like for radar. How might these different antennas allow me to blast microwaves at something to make it hot? Issues are directionality and power transfer efficiency AFAIK. Assume we start with a magnetron.

 Post subject:
Posted: Mon Feb 07, 2005 12:56 pm 
Pretty simple, really.

1) Use directional antenna like parabolic.

2) Match impedance of antenna to object to be "heated" in the near-field (forget far-field for reasonable power levels).

3) Match power amplifier output to antenna input impedance.

4) Turn on power switch.

5) Cook to your preference (a little darker to kill mad cow virus).


 Post subject:
Posted: Tue Feb 08, 2005 2:55 am 
Sounds well and good but your plan requires a different antenna for each item to get cooked. Besides, how do you calculate the impedence of a rock or a brick? Wouldn't it change depending on volume too?
Also, if using a surplus oven magnetron, there is no tuning possible AFAIK.

 Post subject:
Posted: Sun May 29, 2005 5:42 am 
I certainly hope I am not too late on this, but PLEASE BE CAREFUL! do not operate the device unless cleared away. No microwave oven magnetron is safe enough to operate in open field without getting clearance of at least 30 feet.

Please ensure your safety first!

One more thing,

What gets hot in an oven, is what contains water.

Water gets tuned in 2.4 GHZ, and friction of the ringing molecules mates it heat.

any sat dish larger than 1.2m would be sufficien enough (angle of main lobe ~20 deg. @ 2400 for -6db, but remember you'll be spreading 100's of watts ERP in an angle of about 100deg. from the center.

I also estimate about 20 - 40 Watt leakage from the feed mounting arm, which will finally end up spreading all over the place...

Do you really need to do this?!?

Posted  11/12/2012