[opendtv] Re: Wireles to DTV Inteference
- From: "Dale Kelly" <dalekelly@xxxxxxxxxxx>
- To: <opendtv@xxxxxxxxxxxxx>
- Date: Sat, 03 Sep 2005 08:34:55 -0700
You have as much info as I. The report, while lacking technical detail,
provides
a summary of test results that corroborate the recent CRC study predicting
such
interference. I personally predicted the potential for such interference
when the
service was announced but rather than using test data I simply used an
old farts intuition based upon past experiences, for what that's worth, and
I'm clearly not surprised.
Remember, you are dealing with "unlicensed" services and devices. I wouldn't
be so optimistic that everything will work as advertised. Do you recall the
CB radio service's problems and also the more recent unlicensed 2 GHz Spread
Spectrum
microwave service, that is an interferer to the licensed Broadcast
Auxiliary services
due to the "creative" use of HPA devices and high gain antennas?
.
-----Original Message-----
From: opendtv-bounce@xxxxxxxxxxxxx [mailto:opendtv-bounce@xxxxxxxxxxxxx]
On Behalf Of Craig Birkmaier
Sent: Saturday, September 03, 2005 4:31 AM
To: opendtv@xxxxxxxxxxxxx
Subject: [opendtv] Re: Wireles to DTV Inteference
Dale
Enquiring minds want to know.
Does the test scenario used by MSTV even come close to matching the
real world applications for sharing broadcast spectrum that the FCC
is "authorizing?"
I was under the impression that the service would most likely involve
some form of competition for broadband access, with service providers
operating agile radios to deliver the bits to agile receivers. These
transmitters would require proper filtering and would be required to
detect higher priority use of the channels and move to other channels
if there is any chance of causing interference. I have never heard
that this spectrum would be used for in-home wireless routers.
Do you have any more info on this?
Regards
Craig
P.S. Just for the record, broadcasters ALWAYS come up with tests that
prove there will be interference, as we saw with low power FM and the
terrestrial sharing of DBS spectrum. And dare I mention the MSTV
tests of ATSC and COFDM?
At 10:10 AM -0700 9/2/05, Dale Kelly wrote:
>As predicted...
>MSTV video shows "Neighbor's Static" interferes with DTV reception
>
>Sep 2, 2005 8:00 AM
>RF Update e-newsletter
>If a picture is worth a thousand words, then a video recently posted on the
>Association for Maximum Service Television speaks volumes about the likely
>interference unlicensed radio devices, such as wireless Internet enabled
>laptops, operating on "vacant" broadcast channels will cause to DTV
>reception.
>The video, "Your Neighbor's Static," shows significant real-world
>interference to reception of DTV transmissions in a two-story Washington,
>D.C. townhouse. It starts with a test device emitting control signals below
>the strength of the FCC proposed limit of 200 microvolts/meter being turned
>on in the same room as a new DTV set tuned to the over-the-air DTV
>transmissions of several area channels. The test device simulates
>out-of-band spill over interference generated by a high power unlicensed
>device operating on a "vacant" TV channel in a band envisioned for such
>devices at the FCC and in Congress.
>The effect of the interference from the test device varied from DTV channel
>to DTV channel, but in all instances it was noticeable and unacceptable.
>Sometimes, the audio portion of a DTV program cut in and out. On other
>channels, pictures broke up or froze.
>Throughout the video, the transmitter and antenna are moved farther away
>from the DTV set - first into the next room over, then two rooms away, next
>upstairs into a bedroom and finally to into an adjacent home. In all
>instances, the interference remained.
>The video corroborates research by the Communications Research Center in
>Canada which found that higher power unlicensed wireless devices
>"desensitize TV tuners over a wide area." According to the video, the
>research center found interference to DTV receivers up to 78ft from such a
>device.
>The video also shows the same test device generating interference to
>reception of analog TV transmissions.
>According to MSTV president David Donovan, the video was prepared to remind
>members of Congress and policymakers that a spectrum allocation for
>unlicensed wireless devices that results in more interference in the
>broadcast band would have a significant detrimental impact on digital sets
>and a negative effect on the sale of digital-to-analog converter boxes that
>Congress is relying on to advance the shutoff of analog TV service.
>In a worst case scenario, consumers experience interference from such
>unlicensed devices would think there was a problem with their newly
>purchased DTV sets, return them to retailers and retard the transition
>process.
>To view the video, visit www.mstv.org <http://www.mstv.org> .
>
>
>
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>
>
>
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