[RFI] RFI in the news

Charles Coldwell coldwell at gmail.com
Fri Dec 6 21:26:41 EST 2013

On Dec 6, 2013, at 7:14 PM, "W5JR.Mike" <w5jr.mike at gmail.com> wrote:

> This is the great "TV White Spaces" project.

I noticed that; the article says "Those channels are transmitting on the same 700MHz spectrum also used by Verizon …."

Quoting Wikipedia (http://en.wikipedia.org/wiki/United_States_2008_wireless_spectrum_auction):

"The 700 MHz spectrum was previously used for analog television broadcasting, specifically UHF channels 52 through 69.  The FCC has ruled that the digital television transition has made these frequencies no longer necessary for broadcasters, due to the improved spectral efficiency of digital broadcasts.[3] Thus, all broadcasters will be required to move to channels 2 through 51 as part of the digital TV transition."

> And again, the traditional cable TV plant, while using DTV like signaling, still utilizes the same channel assignments as over the air broadcasts. So, more interaction between a wireless phone/tablet and a cable system is on the horizon. 

A little digging around on Wikipedia finds that the WRAL Raleigh OTA broadcasts are at 674-680 MHz (digital channel 48).  The interference seems to suggest that Time Warner Cable must use a different frequency on their plant; as you and W5JR have both pointed out, cable companies are still using the 698-806 MHz frequencies that were reallocated from UHF channels 52-69 to Part 90 Land Mobile Radio Service.

I also notice that ATSC channels occupy 6 MHz of bandwidth, whereas DTV (DVB-T) channels use 8 MHz -- I don't which bandwidth the 64/256-QAM signals on the cable plant use.

This probably belongs on the tower talk reflector, but WRAL was once before notorious in the news a couple of decades back:


Charles M. Coldwell, W1CMC
"Turn on, log in, tune out"
Belmont, Massachusetts, New England (FN42jj)

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