[opendtv] Re: White spaces and 700MHz D Block could be part of new US spectrum plan

  • From: "John Shutt" <shuttj@xxxxxxxxx>
  • To: <opendtv@xxxxxxxxxxxxx>
  • Date: Tue, 29 Sep 2009 13:38:14 -0400

What if this gizmo is working fine, but the user turned it on at 1 AM, after I turned off my transmitter for the night? (Not all stations broadcast 24/7.)


John

----- Original Message ----- From: "Manfredi, Albert E" <albert.e.manfredi@xxxxxxxxxx>
To: <opendtv@xxxxxxxxxxxxx>
Sent: Tuesday, September 29, 2009 12:32 PM
Subject: [opendtv] Re: White spaces and 700MHz D Block could be part of new US spectrum plan


Let's add another part to the question:

The broadcaster uses a mesh of , say, three medium power sticks,
say 10 KW ERP, and the closest to you is 10 miles away. Your
neighbor has a handheld, auto-detecting gizmo that is in a poor
signal reception part of his apartment, so it doesn't detect
that transmitter. So, from a distance of 10 feet of your receiver,
he starts blasting away at a "mere" 100 mW (white space devices
can go a high as 1 watt, by the way).

Make this easy, biased towards your intended result: assume only
free space losses.

By how many dB will he swamp your desired TV signal?

Now let's assume the gizmo works fine, detects a truly free channel, and begins using that channel. And let's assume that there's a broadcast station operating at any of N +/- 1, N +/- 2, N + 7, N - 6 (or whatever were the more vulnerable adjacencies the FCC found in actual receivers), or a combination of these.

At the power levels given above, will the TV be swamped by interference, if the device is trying to use one of those more vulnerable frequency channels?

Are there any other likely problems, given the prevalence of single-conversion receivers, with IM3 products being created by the additional RF emissions?

Bert


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