Slashdot is powered by your submissions, so send in your scoop

 



Forgot your password?
typodupeerror

Comment Re:Physics puts enormous limits on using 30-300GHz (Score 1) 33

Indeed. In that paper I linked to they specifically mention 60 GHz as a great re-use candidate exactly because the attenuation due to atmospheric gases/water is so horrendous.

I don't think your assertion that "2.4 GHz was opened up because of its high absorption by water molecules" is entirely true. It's a fact that water does absorb some power from 2.4GHz RF, but the reason microwave ovens are there is because it's dead center in an ISM band where things like that are allowed. There is no absorption peak for water at 2.45 GHz. The caption for figure 1 in the second link sums it up nicely: "The frequency for maximum dielectric loss lies higher than the 2.45 GHz (wavenumber 0.0817 cm-1, wavelength 12.24 cm) produced by most microwave ovens. This is so that the radiation is not totally adsorbed by the first layer of water it encounters and may penetrate further into the foodstuff, heating it more evenly; unabsorbed radiation passing through is mostly reflected back, due to the design of the microwave oven, and absorbed on later passes." If there were a peak at 2.45GHz, you'd boil the water off the first few mm of food and progressively leatherize the food all the way to the center.

Comment Re:Physics puts enormous limits on using 30-300GHz (Score 1) 33

Too cool! I visited the VLBA radio telescope on St. Croix when I was there and had a long, interesting chat with the tech on duty. I love how all the LNAs are liquid helium cooled in the broiling heat of the tropics. He did mention that they didn't bother with 96 GHz (I think it was) due to the extreme absorption there.

Comment Physics puts enormous limits on using 30-300GHz (Score 4, Informative) 33

The FCC has a publication on the behavior of RF in the 30-300GHZ range, and the outlook is not rosy. Atmospheric gases, water vapor, rain drops, foliage, and other attenuation and noise sources make these frequencies problematic for medium- to long-range, high speed comms.

Using 60 GHz is interesting because it's attenuation is so high it can be reused every 4 km.

Slashdot Top Deals

Old programmers never die, they just branch to a new address.

Working...