[opendtv] Re: The "real" problem with OFDM in the U.S.
- From: "Dale Kelly" <dalekelly@xxxxxxxxxxx>
- To: <opendtv@xxxxxxxxxxxxx>
- Date: Tue, 15 Mar 2005 14:49:08 -0800
I previously wrote:
>coverage could be significantly improved by using synchronous
>repeaters, distributed transmission or a combination of both.
>In some cases, translators will also be used but they are not the major
>solution. Of course, this is predicated upon the availability of DTV
>receivers with acceptable performance, which the current crop of
>Plug and Play receivers likely will not exhibit.
Clarification:
Translator channels are generally no longer unavailable in most markets
but where we currently use them, they are; a) used to extend a stations
overage into areas where terrain shields the main signal and b) often they
extend the signal to portions of the market that are beyond the station
grade B contours, which in many western markets is a common occurrence*.
In case a.) one could sometimes replace the translator using a simple on
channel repeater but often that won't work due to the fact that a degraded
main signal still exists in that location and will interfere with the
repeater.
In case b.) one is not allowed to use an on channel signal to extend a
stations authorized coverage area, for obvious reasons.
*Example, the San Francisco market is approximately 175 miles in
length and numerous terrain obstructions exist. Los Angeles
exhibits similar problems where distance and topography block stations
signals from many large populations, as happens in many other western and
mid western markets.
----- Original Message -----
From: "Dale Kelly" <dalekelly@xxxxxxxxxxx>
To: <opendtv@xxxxxxxxxxxxx>
Sent: Tuesday, March 15, 2005 12:37 PM
Subject: [opendtv] Re: The "real" problem with OFDM in the U.S.
> Bert wrote:
>> Perhaps Dale can expand on the issue of market overlap in the area he
>> serves - I believe it is Seattle.
>
> You must have me confused with someone else, I'm the retired director of
> engineering for a company that owns twenty TV stations across the country,
> including Los Angeles, San Francisco-Sacramento, Houston, Greensboro,
> Fresno, Omaha, etc, etc.
> Each market has unique coverage issues but in almost every case, coverage
> could be significantly improved by using synchronous repeaters,
> distributed
> transmission or a combination of both. In some cases, translators will
> also
> be used but they are not the major solution. Of course, this is predicated
> upon the availability of DTV receivers with acceptable performance, which
> the current crop of Plug and Play receivers likely will not exhibit.
>
>
>
> ----- Original Message -----
> From: "Craig Birkmaier" <craig@xxxxxxxxx>
> To: <opendtv@xxxxxxxxxxxxx>
> Sent: Tuesday, March 15, 2005 5:41 AM
> Subject: [opendtv] Re: The "real" problem with OFDM in the U.S.
>
>
>> At 1:33 PM -0800 3/8/05, Dale Kelly wrote:
>>>Bert wrote:
>>>> So bottom line, if you have to cover large markets
>>>> while making efficient use of frequencies, big sticks
>>>> are a reasonable approach. Especially if these can be
>>>> assisted by on-channel repeaters, to improve the
>>>> signal level in challenged locations.
>>>
>>>You have it right, in my opinion.
>>>Many large big stick markets have marginal DTV C/N in the more distant or
>>>shielded portions on their market. This condition can impact a
>>>significant
>>>portion of their total coverage area, where significant population
>>>clusters
>>>might exist. Properly designed on channel repeaters, together with
>>>advanced
>>>receivers such as the 5G, can significantly increase useable C/N ratios
>>>to
>>>these locations and greatly simplify the antenna system hardware required
>>>to
>>>achieve reliable service.
>>>Of course, as you say, such a system must be designed without creating
>>>additional interference and that can often be accomplished.
>>
>> I tend to agree with Dale that a big stick with gap fillers would be
>> the appropriate solution for HIS market.
>>
>> Perhaps Dale can expand on the issue of market overlap in the area he
>> serves - I believe it is Seattle.
>>
>> What is the overall size of the market (geographically - not population)?
>>
>> What are the adjacent markets, and the distance to their transmitters?
>>
>> Would his station take advantage of an SFN to deliver sub-market
>> services to the communities within the larger coverage area? This
>> assumes that the repeaters would not simply replicate the big stick
>> signal, but rather, would be on different channels so that local
>> content and commercials could be inserted into the programming
>> originating from the main transmitter, AND that localized content
>> could be delivered on sub-channels of the multiplex.
>>
>> As I continue to explain, each market is unique and the design of the
>> transmission network must be optimized ofr the market conditions.
>>
>> Regards
>> Craig
>>
>>
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>
>
>
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