Doug Lung /
07.25.2013 03:50 PM
RF Shorts for July 26, 2013
A review of RF-related news during the past week
IEEE Spectrum Magazine Examines Mobile TV
Stephen Cass describes his experience with Escort's $100 MobileTV dongle on a high-speed Acela train trip from Boston to New York City in Review: MobileTV – Watching broadcast TV on your iPhone in a July 22 posting on spectrum.ieee.org. As appropriate for a technical publication, Cass takes time to explain the challenges of mobile DTV, and rather than just complain about the lack of available channels, he says, “Developed in the early to mid-’90s, these standards [8-VSB transmission] assumed that television sets would remain in one place when in use. Consequently, phenomena such as Doppler shifting of the broadcast signal can disrupt reception when the receiver moves around. In 2009, a mobile-friendly version of the U.S. digital TV standard was released. However, deployment has been slow, because it requires equipment upgrades that many broadcasters were reluctant to make so soon after the major expense of switching from analog to digital transmissions.”

Regarding the train trip, Cass writes, “I tested the MobileTV during a train ride on the Acela Express service between Boston and New York City. This train can reach speeds of up to 240 kilometers per hour. Not surprisingly, reception suffered when the train went through ¬culverts or tunnels, but it appeared ¬unaffected by the movement of the train itself, with good picture and sound quality. The signals faded completely a little beyond 23 km from Boston’s city center. As there are no upgraded stations between Boston and New York, it wasn’t until I drew close to the Big Apple that I could begin to watch television again, this time about 50 km away from the city center.”

His review is positive and he concludes with “The ability to watch broadcasts while out and about during times such as the a¬ftermath of an explosion or power failure, instead of trying to glean information byte by byte via a smartphone ¬browser, is an appealing one indeed.”

HAARP Temporarily Silenced
Alaska Public Media reported last week HAARP Facility Shuts Down. It said, “The High Frequency Active Auroral Research Program, or HAARP facility, shut down last month. The official in charge of the military research facility near Glennallen isn’t talking, but the closure appears to be short term.”

TheRepublic.com has more details in an Associated Press article Ionospheric research program shut down, not clear how long closure will last. It and other Websites note the shutdown may be due to a change of contractors.

The facility's website, http://www.haarp.alaska.edu/ appears to have been shut down as well. HAARP is funded by the University of Alaska, the U.S. Air Force, the U.S. Navy, and the Defense Advanced Research Projects Agency (DARPA). It used high power, high frequency RF to excite the ionosphere. The unusual facility and its military funding led to some wild conspiracy theories as to what those scientists were really up to. Alaska Dispatch has a nice summary of HAARP conspiracies: Guide to most far-out theories behind government research in Alaska, including creation of earthquakes, hurricanes and even mind control.

As I was wrapping up this week's RF Report Brian Dodson at gizmag.com reported HAARP ionospheric research program set to continue, that, “According to HAARP program manager James Keeney, the facility is only temporarily off the air while operating contractors are changed.”

Dodson provides an excellent, detailed description of HAARP, with illustrations. He explains, “The transmitter is roughly as powerful as the largest military radars, generating up to 3.6 MW of RF power in the 2.8 to 10 MHz band. HAARP is restricted to operations only at specified frequencies in this band. The power isn't what makes HAARP different. The credit for that goes to HAARP's phased array antenna. Consisting of 180 individual dipole antennas placed in a field roughly 13 hectares (33 acres) in size, this array acts as a highly directional antenna, with a beamwidth of about five degrees. By the time the RF energy reaches the ionosphere (say, at an altitude of 200 km /124 mi just for this example), the size of the radiated spot is about 18 km (11 mi) in diameter, and the power density is roughly 14 milliwatts per square meter. As the ionosphere is opaque in HAARP's frequency band, it absorbs nearly all of the incident power.”

Comments and RF related news items are welcome. Email me at dlung@transmitter.com.


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