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Hi All,


Until recently I thought that all HDTV was broadcast in UHF. I was all set to order a DAT75 antenna but now I am not so sure what is what.


I saw mention that channels below a certain number (14 I believe) are VHF. Is this true for HDTV?


Lets take the example of KWYDT out of Philadelphia. Titantv lists this as channel 26 but also as tuner channel 3-1. So, which would it be 26 on UHF or 3 on VHF?


Thanks in advance for helping clear my muddled mind.
 

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Primarily digital transmission is UHF, except for select markets, like Atlanta where NBC is broadcast on VHF. 28 is UHF but I am willing to bet it's analog counterpart is channel 3-VHF. Generaly they map to the familiar channel number.
 

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The first number on titantv is the actual channel number the station is being transmitted on. If that number is greater or equal to 14, then the station is UHF. The second number (in orange) is the number which the tuner will remap the station to. For example, in Boston, PBS transmits its signal on channel 19 (UHF) but it shows up as channel 2-1 on my tuner.


For antenna selection, only pay attention to the first number.
 

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You can use this site http://100kwatts.tmi.net/listings.html

to find the real channel for your market. There are digital stations in the channel 2-13 area (VHF). There are more in the ch14-69 area (UHF).

As an example we have a VHF analog ch4. Their digital maps to ch4-1 but the real RF channel is 35. Then on the other side we have an analog VHF ch8 with their digital mapped to ch8-1. Their real RF channel for digital is ch9 VHF. Each market is different so ck the above site and make you a cheet sheet to see what your area looks like.

JStigler
 

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Thanks for the info on channel numbers showing up. Now I know why

DT 46 shows up on the display as 13-1, and 9 shows as 8-1, but then,

was doesn't 25 show as 6-1 ??
 

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Its up to the station to enter the mapped channel number into their PSIP info. Some station's don't do it, maybe due to lack of know-how or laziness. I'd actually wish they all used the physical channel number and not the re-mapping, it can cause problems if they enter the wrong number.
 

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Keep in mind as well that after the transition period, the stations may may move back to their original frequency. So, while you might have all UHF now, a couple of years from now you might have a mix of UHF and VHF. Just something to keep in mind for down the road.
 

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Best to get a good UHF antenna, such as Televes Dat75 now..with the CM 7777 pre amp if you need one. The 7777 has 2 inputs; 1 for UHF and 1 for VHF. They are combined inside the amp and come out as combined line. I have left room on the mast for a VHF (only) antenna in the future..when needed. In general, separate UHF and VHF antennas will give better peformance than a combined antenna. It also seems to distribute weight somewhat better on the mast.
 

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One proposal being considered by the FCC would redefine the digital TV spectrum as Ch. 7-51. Besides the great benefit of eliminating the very problematic VHF low band (Ch. 2-6), this would also make TV antennas more compact and wind-resistant. Maximum element width would not exceed 3' - quite an improvement over today's 9' monsters. --- I have noticed that many major TV markets currently have a single VHF digital channel. Examples are WBBM-DT3 here in Chicago and WFAA-DT9 in D/FW. It's quite possible that these FCC VHF channel assignments were experimental - to see how digital TV transmissions on these lower frequencies work out. We early adopters who own digital TVs and OTA tuners in large cities may be FCC guinea-pigs! On the basis of our very problematic experience in Chicago with digital channel 3, it seems that the VHF low band should be eliminated. Would some of you that have local digital VHF channels (2-13) tell us how these are received in your areas in comparison to your UHF digitals?
 

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Quote:
Originally posted by jurassicjockey
Keep in mind as well that after the transition period, the stations may may move back to their original frequency. So, while you might have all UHF now, a couple of years from now you might have a mix of UHF and VHF. Just something to keep in mind for down the road.
This is a good point - and one that has seemingly been somewhat forgotten or brushed aside. Is there an official FCC edict pronouncing what happens at the end of the transition period?


Take the case where a station has been broadcasting an NTSC signal on VHF for a very long time (more than 40 years in many instances) and now is using a UHF channel for their digital/HD signal. Is the FCC to require that such a station relinquish their VHF allocation for their new UHF allocation? Does the station have the choice to relinquish the new UHF allocation and begin broadcasting their digial/HD signal on their old VHF allocation in place of the old NTSC signal?


If such a station were to perform all of their transition testing on a UHF allocation, and then at the end of the transition period relinquish the UHF allocation and begin transmitting their new digital/HD signal on the old VHF allocation, the testing performed on the UHF allocation would be at least somewhat invalidated (due to the different frequencies).


For a given amount of power applied to a transmitter, the resulting reception range and signal strength at a given distance will vary with the transmitter's frequency. This will also affect the station's bottom line as a result of the amount of power required (hence electricity costs - $$) to cover a given market area. With electricity costs in mind, UHF transmission would be preferable (and possibly a big savings for a formerly VHF station).
 

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Originally posted by TopJimmy


For a given amount of power applied to a transmitter, the resulting reception range and signal strength at a given distance will vary with the transmitter's frequency. This will also affect the station's bottom line as a result of the amount of power required (hence electricity costs - $$) to cover a given market area. With electricity costs in mind, UHF transmission would be preferable (and possibly a big savings for a formerly VHF station). ]


Don't the higher frequencies actually require more power for equal coverage? Typical ERP for analog channels has been: 100 KW for VHF low band, 300 KW for VHF high band, 1000-5000 KW (1-5 megawatts) for the UHF band.
 

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There was much discussion with the FCC years ago about recovering VHF channels post-DTV transition. I don't know how it all fell out, but I seem to recall that low-VHF (chans 2-6) are going to be removed from TV broadcast allocation and designated/sold for other communication services.


Gerald C
 

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Magic,

You said you left room for a VHF antenna, exactly how is this done and how do you attach 2 antenna to a mast. I'm trying to visualize ot because that is probably the ideal setup for me.
 

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How about this idea that I have been thinking for sometime......


Why not create a clear channels high power digital TV channels allocated for channel 2 to 6 up and run up to 100 KW or better ERP for long range Transmission covereges?


Only the few stations will get the best covereges if they will broadcast news and weather and sports in the regonal areas or greater via digital clear channels broadcast.


That would be the best way for the if the satellites were knocked off the air and use the back up VHF low band for long ranges covereges "Great for national security EM broadcast system"


By using VHF low band as for vital information and fill in covereges in the rural areas as well for back up EM, transmission.


Let me know what you think?


12-9-02

"73'S N5XZS"

From Timothy C. Johnson

Live Long and Prosper.....
 

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Quote:
Originally posted by N5XZS
Let me know what you think?
Works for me. I wonder if this has been considered by the FCC?
 

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Quote:
Originally posted by N5XZS
How about this idea that I have been thinking for sometime......


Why not create a clear channels high power digital TV channels allocated for channel 2 to 6 up and run up to 100 KW or better ERP for long range Transmission covereges?
It is thought that channels 2-6 are not really conducive to reliable DTV reception due to impulse noise and when the band opens up. As you probably already know, 2-6 gets hammered pretty bad with analog interference when tropo or the E layer cranks up. It is felt that it would completely obliterate a digital signal and this why most large companies have asked to move to higher channels. WBBM DT-3 Chicago is a great example. CBS has tried on SEVERAL occasions to get the FCC to let them change channels only to be turned down all times and if you follow the Chicagoland threads, WBBM DT-3 is having a tough time right now. FOX had WTTG (TV-5) Washington moved from DT-6 to DT-36 because of that very reason.


It is a great idea on paper, but in reality, it is much harder to make work.
 

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gassdoc..


I have a support mast with my rotator (and a support bearing above it) ; I have about a 7 foot mast coming up from the rotator with my TelevesDAT75 antenna at top of this mast. About 2.5 feet down from antenna I have a CM 7777 pre-amp which has 2 inputs..one for UHF and one for VHF with a single combined output. There is room left on mast for a VHF antenna when I need 1 in the future. I will experiment how far to place it from UHF antenna.
 

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I like N5XZS's idea ... even with the Sporadic E and impulse noise interference issues -- Tropo is everywhere on the TV bands. There are some rural areas who can receive OTA signals only on Low-VHF, due to various issues such as distance and severe terrain blockage due to mountains.


Or, Another "more crazy" idea, how about a "Nostalgia NTSC" band on 2-6?


Anyhow, I find it interesting that a number of DTV stations(some relatively recently) have petitioned FCC for an DTV allocation change TO Low band VHF:

http://www.fcc.gov/mb/video/files/dtvchan.html
 

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Originally posted by Nitewatchman


Anyhow, I find it interesting that a number of DTV stations(some relatively recently) have petitioned FCC for an DTV allocation change TO Low band VHF:


This is disturbing and will probably undermine the sentiment to redefine the DTV spectrum as Ch 7-51. The primary motivation here is probably the much lower ERP requirements on the VHF low band, maybe less than 5% of UHF levels for equivalent coverage. This major reduction in power cost can do a lot for a station's bottom line over the years.
 
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