Burt, The original poster suggested using two cups- one empty cup with the paint on it, and a second cup with water in it to act as a load. Apparently, some readers thought that the painted cup would have water in it. Not so.
Most microwave ovens I've bought over the years- including one of the original Amana Radaranges- included stern warnings to never operate the oven without something in it. I have seen a few microwave ovens blow fuses due to magnetron arcing, when there wasn't enough of a load in the oven cavity. I think it makes perfect sense to operate a power oscillator into a suitable load. Oven magnetrons are not cheap! 73, Eric Lemmon WB6FLY -----Original Message----- From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Burt Lang Sent: Sunday, May 04, 2008 2:54 PM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] Re: antenna question - Dip It and Scotch Kote Think about it. If you expect the water to act as a heatsink, it would require the cup to transfer heat thru its material. Heat can go both ways and you will never know if heat generated on the outside is heating the water or vice versa, the water is passing thru the cup to the outside. Put a coffee cup of water into your microwave and see how hot the outside of the cup gets when the water is heated. Even if you use a foam cup to isolate the outside from the inside and are using the water to provide a load on the magnetron (which it doesn't need), there will be enough moisture in the foam for it to heat up and probably melt leaving a real mess to cleanup. Burt>>> MCH wrote: > You don't care if the cup of water heats up - you are looking to see if > the painted cup heats up. The water is only there to prevent burning out > the microwave. > > Joe M. > > Burt Lang wrote: >> Fine except for one problem. Water is an excellant absorber of the >> microwaves used in the microwave ovens (2.45 GHz) So your water will >> heat up quickly irregardless of the coating. The only substances that >> are better absorbers of that frequency are animal or vegetable fats >> because they contain 9 times the molecular bonds (the O-H bond) that >> actually do the absorbing. >> >> Burt VE2BMQ (who used to be a professional chemist) >> >> IM Ashford wrote: >>> Paint a polythene cup with your favourite antenna covering. Let it dry >>> and put it into the microwave oven along with a cup of water (to act as >>> a dummy load) >>> Cook for 1 min on max power. >>> If it gets even slightly warm its no good for antennas. >>> >>> er.. can I please have an award for the first cooking recipe to get past >>> the moderator on repeater-builder >>> >>> Ian >>> G8PWE
