[opendtv] Re: Tired of the Silver Sensor?
- From: Richard Hollandsworth <holl_ands@xxxxxxxxx>
- To: opendtv@xxxxxxxxxxxxx
- Date: Fri, 19 May 2006 23:17:52 -0700 (PDT)
Some additional answers embedded...
holl_ands
Cliff Benham <cbenham@xxxxxxxxxxx> wrote: OK, once again it's time for me to
ask the questions I've posed to this
list for 6 years and which, to the best of my recollection NO ONE
has, will or wants? to answer.
1. How good is ATSC reception going to be once the analog cut-off date is past
[whenever that may be] AND after all the "temporary" channels have been given
back AND when many of the OTA DTV stations are then transmitting on VHF
frequencies?
A1: VHF has advantage of longer range and "bends" around obstacles better. As
stated already, demise of NTSC means elimination of its "peaky" interference.
DTV tolerates co-channel and adjacent channel DTV quite well. Lower VHF band
has higher impulse noise, but ATSC is much more tolerant to impulse noise than
COFDM.
2. How many of the DTV stations now operating on UHF channels will
ultimately end up on VHFs at the real end of the transition?
A2: Results of First Round Channel Election were reported in TV Technology (and
has only slightly changed since then):
http://www.tvtechnology.com/features/On-RF/F_Lung-04.06.05.shtml
Very few CH2-6, but quite a few CH7-13.
3. How much of the testing for DTV has been done at VHF frequencies or was all
of it done at UHF?
A3: The various reported tests nearly all included VHF and UHF
channels....although most were done at very low power.
a. www.atsc.org lists numerous reports incl. fol. dated Dec 2000:
http://www.atsc.org/news_information/papers/2000_vsb_comparison_report/VSB_COFDM_Project_Comparison.pdf
b. Brazil 2000 Test Report: ATSC vs DVB-T (119 pgs):
http://www.anatel.gov.br/english_site/publications/public_consultation/tvd_ranalises_ing.pdf
c. Australia 1998 Test Report: ATSC vs DVB-T (dtbfield.doc) (30 pgs):
http://happy.emu.id.au/lab/info/digtv/files/
d. Summary of DVB-T (et. al.) Field Trials Around the World:
http://www.bjpace.com.cn/data/tec/tec-DVB/DVB%20Publications/DVB-T%20Field%20Trials%20Around%20the%20World.pdf
e. Zenith 2003: Excellent Summary of Commercial Broadcasters On-Air Tests (19
pgs):
http://www.zenith.com/digitalbroadcast/downloads/ATSC%20Field%20Test%20Results.pdf
f. Zenith 2003: ATSC Seminar--See on-air test summary towards end (265 pgs):
http://www.zenith.com/digitalbroadcast/downloads/Seminar%20Slides.pdf
[Everything you ever wanted to know about ATSC, but were afraid to ask....]
4. Did the VHF tests, if any were done, reveal any problems with VHF DTV
reception that were not seen in the UHF tests?
A4: Hard to say, most were not at full power....
5. What happens relative to consumers [after the scenario in question 1
comes to pass] when all the cute little indoor or roof mounted outdoor UHF
antennas that people installed specifically to watch OTA DTV with no longer
receive all the stations because some are now operating on VHF channels?
5. Will people rush right out and buy more 65 inch rabbit ears for the
top of their 65 inch flat panel TVs or huge Zig-A-Log rooftop antennas
so they can once again tune in the suddenly missing DTV programs that are now
on channels 2 through 13?
A5: Depends....many will find that their "UHF" antenna also works "good enough"
for VHF channels...perhaps even lower VHF...
Most DMA don't need much of an "antenna" for VHF....it's not just a joke that
Kerry Cozad started with a coat hanger in his antenna measurement test....and
newer receivers are much more tolerant of multipath than NTSC.
6. Was all of this ever really thought out or even discussed or
considered by the ATSC, the FCC or the NAB with the future of OTA DTV for the
consumer in mind?
A6: WHAT, didn't you get the MEMO re need for VHF and UHF antennas??? You were
ASSUMED to be already using your 30-year old, roof-mounted VHF antenna....
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