[mythtv-users] Comcast just made things worse

[Brian Wood]

On Saturday 08 May 2010 12:53:45 pm Douglas Peale wrote:


> 
> VHF Low (2-6) is uncommon. The FCC is discoraging its use for major
>  stations.

The OP mentioned the situation with channel 6 in Philadelphia, a bad situation 
that I am unsure about how it came to pass.

Philly has always had an unusual broadcast situation. One of the only 2 
stations east of the Mississippi with a "K" call sign (the other is KDKA in 
Pittsburg), and the musical chairs network affiliations a few years ago (similar 
to what happened in Denver, and for similar reasons (ownership changes and 
agreements)).

>  VHF High (7-13) is still being used (though I wish it weren't).

I agree. There were certainly enough UHF assignments available to eliminate 
any need for VHF, not sure why it happened. Perhaps broadcasters lobbied for 
VHF assignments due to lower power costs and/or legacy thinking that VHF is 
"better"?

Power cost for a UHF station is much higher than for a VHF. Not a big factor 
for the major broadcasters, but significant to some of the smaller market 
operators, who sometimes asked for and received authority to run at reduced 
power due to "economic hardship" (This happened in Kingston NY for example).

Reduced power was mandated or allowed for other reasons, for example channel 
31 in NYC, to prevent the radiation levels on the public observation platform 
at the WTC from exceeding allowable limits (not a factor now).

>  VHF High + UHF antennas are about half the size of full range antennas,
>  but UHF only antennas could be much smaller.

I hadn't seen any of these, good to hear that they are available, since as you 
say they can be made much smaller than full-band VHF antennas.

> 
> In my area, channels 7, 8, and 12 are in use.

Unusual to have adjacent channels in use in the same market. This was never 
done with analog assignments. Perhaps you are picking up stations from 2 
different ADIs?

(Cable TV systems can get away with using adjacent channels by reducing the 
power of the aural carrier to 15-17 db. below the visual, as opposed to 10 db. 
down used by OTA analog stations).

The FCC also mandated +/- 10 Khz. frequency offsets to prevent inter-market 
interference with adjacent channels 2 or more markets away, and sometimes 
approved reduced aural carrier power for similar reasons.

Note that 4 and 5 are not adjacent, nor are 6 and 7, due to the frequency 
allocations., so you would sometimes see those combinations approved.