Science Buddies: "Ask an Expert"

So the observation of my project is due soon, and I can not get the data. The microwave leakage detector tells me numbers that jumps around by a lot during my testing at the same spot, therefore I can not put the numbers into data. Also, from my researches, it shows me that cellphones emits radio radiation, not microwave, so I am confused. I called the people who sells the detector and they told me that it is designed only for microwave ovens, so I don't know why this is put up as a link to material.

[Moderator added: project url is: https://www.sciencebuddies.org/science- ... p068.shtml ]

sean.guo - There may be several issues going on here. To answer some of your questions, radio frequency energy emitted by the cell phone (800 to 1900 MHz) and radiation leaking from a microwave oven (2450 MHz) are the same thing, just different frequency. It is non-ionizing electromagnetic radiation. The experiment encourages the student to research ionizing and non-ionizing radiation for a more complete understanding of the difference. The people that sold you the detector are not totally wrong, the instrument was manufactured to measure potentially dangerous radiation leakage from a possible faulty microwave oven. The instrument was designed to operate at 2450 MHz, (the operating frequency of all home microwave ovens) so I don't know what it's performance or characteristics are at 800-1900 MHz, although it probably will register something on the meter (especially a low cost meter).

With regards the numbers 'jumping around', that could be a function of the cell phone and it's constant switching with the cell tower it is using. Even when in standby mode, your phone is constantly 'talking' to the cell towers, so you may get some readings at random times. I also would not speak on the phone when you are making your measurements as modulation effects could be read by the meter as different apparent power levels. Phones may dynamically change power output to adapt to the needs of the cell tower they are communicating with. The title of the experiment is a little misleading as well. I don't think the phenomena of getting different power readings at the bottom, or the top, or the back or front of the cell phone really suggests there is unwanted 'leakage' occurring in the same sense that you might be investigating a microwave oven leakage due to inferior seals or shielding. Antenna characteristics and the dispersion of the RF signal are not symmetric, so it is likely that you will get different readings in different locations, but I'm not sure what conclusion that leads us to. Even the position you hold the meter can introduce differences. It also has an antenna and the position relative to your cellphone can introduce variables. A cell phone with an obvious external antenna versus one of the slim, popular smart phones with an internal antenna will likely read differently. The experiment also suggests trying a different model phone and comparing results. I can't help you on explaining those differences either. Phones are likely to be somewhat different.

You might want to create your own experiment and hypothesis around on of the phenomena I mentioned, that is the measured power of the cell phone when you are moving from strong signal areas to weak signal areas. The phone may show an interesting ability to increase power in weak signal areas and reduce power in strong signal areas. I don't know what the measured effect would be - maybe that's why they call it an experiment. Do a little more background reading on cell phones, cell towers and you might get some other good ideas. Good luck.

Rick Marz