[opendtv] Re: KKTV Requests Move from VHF to UHF
- From: "Manfredi, Albert E" <albert.e.manfredi@xxxxxxxxxx>
- To: <opendtv@xxxxxxxxxxxxx>
- Date: Mon, 6 Jul 2009 18:15:57 -0400
Dan Grimes wrote:
>>FM radio works, right?"
>
> Not always and very dependent on inside vs. outside and even which
> radio (some are definitely more sensitive than others). Also
> needs a long antenna. And one can't use a directional antenna
> (for fixed locations) because stations are located around the city.
All the more reason not to expect miracles when attempting to transmit
36 times as much bandwidth at roughly the same power levels as FM! Or
even lower power levels than FM.
I was intrigued a white paper, written by the company Doug Lung
mentioned: Axcera. The paper gives results of a straightforward A/110
SFN implemented near State College, PA, and then adds a new twist. It's
a few years old, though.
In the new twist, they use two tiers of repeaters. The main transmitter
is on Ch A. The first tier of repeaters, essentially arranged in a
circle around the main transmitter, on Ch B. The second tier, a circle
beyond the first tier, is on Ch A again. This would be to avoid having
to have a dedicated link between the main studio and all the
synchronized repeaters. This would allow the first stage of repeaters,
for example, to feed the second stage.
http://www.axcera.com/downloads/technotes-whitepapers/hershberger_white_
paper.pdf
The Pennsylvania test of the basic A/110 SFN showed that 4th gen
receivers (which I think refers to the Lynx design) worked well, but
what they call "pre-1st gen receivers" would not lock into the signal
consistently.
Bert
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