RF Shorts - June 24, 2010
June 24, 2010
Distributed transmission and repeaters are being suggested as a way to reclaim spectrum from broadcasters. The FCC's Spectrum Analysis: Options for Broadcasting OBI Technical Paper No. 3 mentioned distributed transmission and a cellular architecture but did not consider it in its spectrum reclamation studies. That may have been wise, given the limitations of ATSC receivers in a multipath environment. Charlie Rhodes has an excellent analysis of this in his article “Will SFNs Work in North America?”
Last week I wrote about concerns of major disruptions due to an expected increase in solar activity in “NASA Official Warns of Solar Storm Effects.” For a doomsday scenario of what could happen, see "Could Super Solar Flares Take Us Back to 5000 BC?" on mi2g.com.
The U.S. Army Signal Corps was created in 1860. The Augusta Chronicle has a great look back at the Signal Corps accomplishments in the article “Signal Corps celebrating 150 years of service.” The Signal Corps is headquartered in Fort Gordon and more than a thousand men and women were expected to take part in this week's celebration commemorating the history of the corps at Barton Field and the Signal Corps Museum in Conrad Hall.
Worried about exposure to RF from cell phones and TV towers? Read Fran John's post “Cell phone radiation danger: true or false” for a discussion of the issue from a different angle. “The power of radio waves falls off as the square of the distance. This means one watt an inch from your head (typical for a cell phone) has the same effect as 1 million watts, 1,000 inches from your head. The strongest TV signals on Sutro Tower run 1 million watts. A thousand inches is about 83 feet. Whether putting your head 83 feet from Sutro Tower every time you talk on the phone bothers you, is up to you.”
Finally, if you've been reading about LTE (“Long Term Evolution”) for 4G communications and want to learn more about how it works, I found a detailed on-line tutorial this week on Commsdesign.com. See “An overview of the LTE physical layer – Part I and Part II,” by Fran Rayal from Telesystems Innovations.