Yes, the absorption is frequency specific. However this specifics shows up at the frequencies of tens of GHz. It is irrelevant to microwave ovens.
Huh? Microwave ovens have nominal frequency of 2450MHz (actually they generate a pretty wideband splash). This is the same ISM band that used by WiFi, Bluetooth and such.
Vladimir Vassilevsky
DSP and Mixed Signal Design Consultant
Hmmm. There is no frequency data on the nameplate of my kitchen unit, so i did some searching. And there they are at 2450 MHz right on top of 802.11g channel 9. The 2160 came from the nameplate data of the last microwave oven that i saw that had a frequency specified.
-- JosephKK Gegen dummheit kampfen die Gotter Selbst, vergebens. --Schiller
antenna
FYI, alt.internet.wireless discusses this topic often.
I prefer the biquad antenna, which you can augment with a dish. I have a short-cut method to build this antenna. With a combination of these photographs and this link, you should be able to figure it out.
Note you don't need to make the loop a square. Use a circle of the same circumference.
There is a disadvantage to using the helix. It will receive both horizontal and vertical polarization. Most sites just send in one polarization. In busy areas, the same channel will be used in different sites with different polarity. Now if you use the helix to illuminate a dish, then the circular polarization is fine and perhaps desirable. That is, you could sniff out signals without the attenuation associated with having the wrong polarization.
That's in the 2110 - 2170 range that is allocated to the downlink signal of UMTS (3G) mobile phones in many countries. Those frequencies were sold for a price that people found surprisingly expensive at the time.
Chris
antenna
Thanks Miso, I'll start lurking there.
martin
It's also plop in the middle of S-band, which is loaded with military radars, and there's an ionospheric window there so there's a lot of demand for uplink/downlink channels.
Cheers! Rich
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