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Re: [RFI] RFI in the news

To: rfi@contesting.com
Subject: Re: [RFI] RFI in the news
From: Charles Coldwell <coldwell@gmail.com>
Date: Fri, 6 Dec 2013 21:26:41 -0500
List-post: <rfi@contesting.com">mailto:rfi@contesting.com>
On Dec 6, 2013, at 7:14 PM, "W5JR.Mike" <w5jr.mike@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 

"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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