## Re: [HDTV-in-SFbay] Re: after the apocalypse

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• Free space path loss (in air or vacuum) is: Loss in dB = 36.6 + 20 log f (in MHz) + 20 log d (in miles) or Loss in dB = 32.4 + 20 log f (in MHz) + 20 log d (in
Message 1 of 20 , Feb 1, 2006
Free space path loss (in air or vacuum) is:

Loss in dB = 36.6 + 20 log f (in MHz) + 20 log d (in miles)

or

Loss in dB = 32.4 + 20 log f (in MHz) + 20 log d (in kilometers)

For KGO-DT, the free space loss at channel 24 (533 MHz) is 9.6 dB
greater than at channel 7 (177 MHz). Assuming they run 316 kW when
they move their digital transmitter back to channel 7, they will have a 7.1
dB advantage over their current 561 kW transmitter on channel 24. In
other words, their signal at 316 kW on channel 7 would be equivilant to
a 3 Megawatt transmitter on channel 24.

Ron

Richard Swank wrote:

> I would guess if you receive KNTV-DT on channel 12 (Rf) you will receive
> KGO-DT on channel 7 (Rf) or KQED ch-9 without a problem. VHF
> propagation is
> better than UHF as the wavelength is quite a bit longer and therefore it
> takes larger objects to reflect it or attenuate it. Just the atmospheric
> air attenuation of Rf signals is a function of the wavelength,
> basically the
> Rf strenght of the transmitted signal attenuates to 1/2 at every
> wavelength
> it travels from the antenna source. Ch-12 wavelength is around 33 inches.
> So by a little over 5' from our antenna the signal strength is 1/4th
> of the
> 101.3KW we are transmitting and every 33" from there on it is 1/2 again.
> Ch-40 wavelength is less than 10" so this attenuation occurs much
> faster as
> it travels through space.
>
> This is why the FCC maximum NTSC power for a High band VHF transmitter
> at a
> height under or equal 2000' is 316KW and at the same time that
> "EQUIVALENT"
> UHF power is 5000KW. DTV power levels are average power and about 1/5
> those
> of these peak NTSC power levels. So DTV power maximums for UHF are
> currently 1000KW but interference maxification studies can modify this
> some.
>
> For instance KNTV did DTV maximization studies prior to our move to Mt.
> Bruno and although our NTSC is operating at an E.R.P. (Effective radiated
> Power) of the 316KW we were able to obtain a license for the DTV
> transmission to be an ERP of 101.3KW. This means our equivalent DTV
> signal
> strength is somewhat larger than our NTSC signal strength in most
> locations.
>
> My assumption is that KGO-DT will also maximize power levels based on
> interference to other broadcasters and since they have owned ch-7
> since day
> one they will likely be able to operate at higher than the 1/5th NTSC
> power
> level.
>
> Since these transmitters operate at about 35-40% efficiency levels at best
> you can probably figure that propagation improvement is not the only
> advantage to being a high band VHF. Monthly PG&E charges are also much
> lower. DTV transmitters in the high band VHF operations will usually be
> solid state instead of tube as well. More reliable and considerably less
> expensive to maintain.
>
> Yes, low band VHF (ch 2-6) propagation is even better than high band VHF,
> for the same reasons, but since bit error rate is "very" critical to DTV
> reception low band VHF to this point hasn't proven very good. This is
> mostly due to things like ignition noise. DTV viewers certainly wouldn't
> like their picture to pixelate and go black every time a truck or car
> drives
> by or the neighbor mows his lawn or runs his blender. If receiver
> manufactures could resolve the error problem most current NTSC VHF
> stations
> would remain on their NTSC channel when DTV takes over.
>
> I do believe that broadcasters will be forced to kill NTSC and make the
> magic switch to their new DTV channels at 00:01 on Feb 17th, 2009. During
> the preceding weeks to this it may mean that neither the NTSC or DTV
> reception between 1:30am and 4:30am will be any good on these channels
> that
> conflict as the stations perform required FCC testing but that is the cost
> of progress so to speak.
>
> Most older high band VHF NTSC antennas and transmitters are not flat
> enough
> (=gain over the 6 megahertz channel band) for good DTV transmission. They
> would probably cause an effective built in error rate to be transmitted by
> the broadcaster. This in turn would make the viewer reception much more
> difficult and cause undue problems to the station. I would therefore
> expect
> most broadcasters like KGO to replace their antennas between now and 2009.
> NTSC works just fine on a DTV antenna so except for the couple of days the
> actual installation of the new antenna takes nobody will notice the
> change.
> NTSC broadcasters pre-distort our signals to compensate for antenna and
> transmitter non-linearity. This works very well in the analog world but
> this trick is not an option for DTV.
>
> I can forsee "new" local DTV channels coming on-line once the current
> double
> locals channels are not in exsistance. Maybe not in SF as there is so
> many
> stations already but there will be freed up UHF channels so it's possible.
> Not all the channels being freed up are above the ch-50 maximum. Of
> course
> the FCC plans on auctioning these off for other services and for big
> \$\$\$\$\$\$\$.
>
> So I wouldn't call Feb 17th 2009 an apocalypse. It will be an interesting
> time for viewers and broadcasters alike however.
>
• Same here, I can get all the SF channels, but no 11 since the X-mtr left SJ. Strange thing is I can get the digital for KSBW is the conditions are right. ...
Message 2 of 20 , Feb 1, 2006
Same here, I can get all the SF channels, but no 11 since the X-mtr
left SJ. Strange thing is I can get the digital for KSBW is the
conditions are right.

--- In HDTV-in-SFbay@yahoogroups.com, "Michael Portuesi"
<mportuesi@...> wrote:
>
> --- In HDTV-in-SFbay@yahoogroups.com, "Richard Swank" <rswank@p...>
wrote:
> >
> > I would guess if you receive KNTV-DT on channel 12 (Rf) you will
> > KGO-DT on channel 7 (Rf) or KQED ch-9 without a problem.
>
>
>
> Considering I don't receive KNTV-DT at all from my location, I'm not
> optimistic about KGO-DT's move to VHF after the analog shutdown.
>
> To be fair, KNTV is on Mt. San Bruno and that's my real problem with
> receiving it. But it really would be nicer if all the local stations
> were broadcasting UHF. It would make it a lot easier for us to receive
> all the stations if UHF were all we had to focus on receiving.
>
> I have a partner who is very adamant about not having a rooftop
> antenna. While I might be able to sell one fairly small UHF outdoor
> antenna, having to install two antennas (or one honking huge combo
> antenna) is a big issue for me. Likewise, I currently use a Silver
> Sensor indoors, and it only receives UHF.
>
> I do wish the broadcasters would think about the viewers when they
> make their channel allocation decisions. Having two frequency bands
> rather than one is a pain.
>
> Michael Portuesi
>
• Where do you live? ... From: thekatdude [mailto:thekatdude@yahoo.com] Sent: Wednesday, February 01, 2006 11:41 PM To: HDTV-in-SFbay@yahoogroups.com Subject:
Message 3 of 20 , Feb 2, 2006
Where do you live?
-----Original Message-----
From: thekatdude [mailto:thekatdude@...]
Sent: Wednesday, February 01, 2006 11:41 PM
To: HDTV-in-SFbay@yahoogroups.com
Subject: [HDTV-in-SFbay] Re: after the apocalypse

Same here, I can get all the SF channels, but no 11 since the X-mtr
left SJ.  Strange thing is I can get the digital for KSBW is the
conditions are right.

--- In HDTV-in-SFbay@yahoogroups.com, "Michael Portuesi"
<mportuesi@...> wrote:
>
> --- In HDTV-in-SFbay@yahoogroups.com, "Richard Swank" <rswank@p...>
wrote:
> >
> > I would guess if you receive KNTV-DT on channel 12 (Rf) you will
> > KGO-DT on channel 7 (Rf) or KQED ch-9 without a problem.
>
>
>
> Considering I don't receive KNTV-DT at all from my location, I'm not
> optimistic about KGO-DT's move to VHF after the analog shutdown.
>
> To be fair, KNTV is on Mt. San Bruno and that's my real problem with
> receiving it. But it really would be nicer if all the local stations
> were broadcasting UHF. It would make it a lot easier for us to receive
> all the stations if UHF were all we had to focus on receiving.
>
> I have a partner who is very adamant about not having a rooftop
> antenna.  While I might be able to sell one fairly small UHF outdoor
> antenna,  having to install two antennas (or one honking huge combo
> antenna) is a big issue for me.  Likewise, I currently use a Silver
> Sensor indoors, and it only receives UHF.
>
> I do wish the broadcasters would think about the viewers when they
> make their channel allocation decisions.  Having two frequency bands
> rather than one is a pain.
>
> Michael Portuesi
>

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