[mythtv-users] VHF, UHF, and digital TV

[Jay Foster]

On 4/30/2015 3:16 PM, dennis wrote:
>
>
> On 04/30/2015 01:27 PM, James Miller wrote:
>> Sort of a general query here, answers to which may aid me in the 
>> future if I will purchase a new antenna. Here is my (admittedly 
>> technically-deficient) understanding of OTA DTV as it relates to 
>> traditional VHF/UHF TV broadcasting in the US. The idea of moving to 
>> DTV is to increase bandwidth availability for other radio frequency 
>> devices like cellular communications and perhaps wifi. So causing TV 
>> broadcasting to switch to digital, which makes transmission of the 
>> signal much more precise and thus has the virtue of freeing up some 
>> bandwidth, was undertaken.
>>
>> As I understand it, the ultimate intention is to get all OTA TV 
>> broadcasting into the UHF range so as, I suppose, to free up the 
>> whole of the VHF band for other radio frequency services. Is that 
>> correct? If so, I was told some time ago that, during initial phases 
>> of DTV implementation, DTV broadcasting will still be done in the VHF 
>> range. Is this also correct? I believe I determined a year ago or so 
>> that, in fact, some OTA DTV broadcasting in my area (upper midwest, 
>> US) is still done in the VHF range.
>>
>> This becomes a question at this point because, during a recent 
>> channel scan, I noted that there are some new OTA stations which are 
>> repetitions of some existing stations. I've been picking up a 10_1, 
>> 10_2, 10_3, and 10_4 (PBS), but now I see there is a 10_11, 10_12, 
>> 10_13, and 10_14 that seem to be the same exact stations. I believe 
>> the 10_1-10_4 stations I've been getting are in the VHF range and I 
>> suspect that the new 10_11-10_14 stations I see may be the new, 
>> UHF-band replacements, and that the two sets of stations may exist 
>> for a time side-by-side, til they phase out VHF-band broadcasting. 
>> Then, all programming for that station will be provided only through 
>> the new, 10_11-10_14 channels. So, do my assumptions about this 
>> matter seem sound?
>>
>> If it is the case that eventually all OTA TV broadcasting will move 
>> to the UHF band, that will influence future decisions about what sort 
>> of antenna I'll need to buy to bring in OTA DTV broadcasting I watch. 
>> Any corrections, clarifications, or modifications on the above 
>> topics/statements will be appreciated. Thanks
>>
>>
> In the Chicago area,  the CBS affiliate ( WBBM-2.1 ) is broadcasting 
> on VHF.    They did move from the VHF-L (2) to VHF-H (12) a couple 
> years ago, but it was  due to interference and lack of coverage, not 
> regulations.    From what I understand, most stations have moved out 
> of the VHF-L (2-6) due to poor reception, but VHF-H is still alive and 
> may be around for a quite awhile. There is talk of extending the FM 
> radio broadcasting into VHF-L frequencies.
>
> I have a UHF/VHF antenna, and expect to continue to need one ( only 
> for CBS ).  It would be nice if they did move everything to UHF, but 
> that not the case where I am at.
>
> Dennis
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In my area, I still have seven VHF digital stations.
The channel numbers that are typically used to tune a station are the 
PSIP (vritual) channel number.  This often differs from the physical 
channel number.  Some TVs/devices allow direct tuning, where you can use 
the PSIP channel number or the physical channel number.  It was somewhat 
typical in the early days to map the PSIP.1 channel to the physical.3 
stream, PSIP.2 to the physical.4 stream, etc.  So if station XYZ was on 
PSIP channel 15.1 (physical 30.3), you could tune it using 15.1 (or 30.3 
if direct tuning is supported).  Some station's PSIP channel major 
number is the same as the corresponding physical channel and some are 
not.  It is all up to the broadcaster.

There was even a time where two stations in my area tried to use the 
same PSIP numbers (different physical channels).  This was great fun.  
Some devices would assign the duplicates to made up PSIP numbers and 
some devices would assign them as duplicates.  A real mess, which has 
fortunately been rectified.

Jay