Reception of Over-The -Air Digital TV

[patric]

quote:Originally posted by Wrinkle



Isn't there supposed to be something else involved on a UHF antenna if it's connected in series with a VHF antenna on the same line?

You can "multiplex" (combine) separate UHF and VHF antennas so that they only require one cable down to the receiver.


An 'active' combiner amplifies the signals beforehand, and is usually mounted at the antenna.  Most Radio Shack stores can show you what this looks like, but odds are you may get a combination UHF-VHF antenna and not have to worry about this at all.

Most TV tuners built within the past two decades (that have a threaded coaxial connector for antenna input) can deal with the combined signals.  

quote:I also get pretty good over air reception, if I can keep DirecTV from interfering with my air signal (mostly at prime time, diagonal lines).
I don't have locals on my DirecTV.

Sounds like the connection between the DirecTV box and your TV is "leaky".  The modulator in your satellite receiver transmits a weak TV signal on channel 3 or 4, which could "beat" against your over-the-air signal (if it leaks out) and create the noise pattern you are seeing.  The fix may involve tightening or re-installing the cable between the DirecTV box and your TV, swapping the cable with one not damaged or defective, or removing any splices or other devices in the cable that may be allowing your DirecTV signal to escape.  Better yet, eliminate the RF (radio frequency) connection and use a Multimedia Cable instead.  

Multimedia cables are actually a set of three cables with color-coded RCA connectors at each end: Yellow for video, and Red and Black(or white) for left-and-right audio.


(newer sets have what's known as an 'S-Video' connection in place of the yellow video plug, and the newest TV's use a connection known as HDMI, but im getting ahead of myself...)


As for local channels on DirecTV, you need at least a 3-LNB dish to "see" the particular satellite with Tulsa's locals, but a lot of people are OK with just using an antenna.

[Porky]

Antennas are actually the best reception for HDTV.

Just be sure you have at least 10-12 dbls with your antenna or you won't be able to pick up the UHF stations very well in digital. It'll be marked on the box the antenna comes with what dbls it is rated at.

I also suggest getting the tube HDTV over the LCD. I have both and you can get a much better picture with the tube at a much better price. Samsung is the only one I know that sales the tube type and it is awesome. Best Buy carries the Samsung tube line in Tulsa. I paid less than $500 for my 27 inch.

[patric]

ATSC (Advanced Television Systems Committee) the international digital television (DTV) standard adopted by the U.S., Canada, South Korea, Taiwan and Argentina, is Broadcast over the air (terrestrial), via satellite or cable.
ATSC transmits in a 6MHz channel and uses MPEG-2 video compression and Dolby Digital audio compression. ATSC was adopted by the FCC in 1996.

[Wrinkle]

Patric,
I am multiplexed now, but still don't get UHF like I should with the big antenna (dedicated UHF) in the attic (tied to a large VHF antenna).

It's that series connection UHF to VHF antenna that I think is messed up, not the multplexed cable from there down. I never quite understood the differences between 75-Ohm and 300-Ohm stuff, but the 300-Ohm (flat two-wire brown ribbon cable) on the UHF connects to the VHF with an adaptor with screws on one side and a coax connector on the other side (75-300 Ohm).

Oddly, the new HD satellite (D10) will require un-multiplexing the coax to receive local channels since the Local Satellite HD will overlap the multiplexed UHF/VHF signal, as I understand things.

IOW, separate run all the way to receiver for OTA UHF/VHF.

In the meantime, I've picked up an H20 Receiver which includes ATSC (OTA HD) not available on the current generation of Receivers (H21/HR21). Even then, the H20 requires BBC Modules on both inputs (SD/HD) to work properly.

I also ran into this: Level 3 to Help Support DirecTV

...which may explain my recent improvement in reception all around. The 'backbone' is local around here.

[Wrinkle]

quote:Originally posted by Porky

Antennas are actually the best reception for HDTV.

Just be sure you have at least 10-12 dbls with your antenna or you won't be able to pick up the UHF stations very well in digital. It'll be marked on the box the antenna comes with what dbls it is rated at.

I also suggest getting the tube HDTV over the LCD. I have both and you can get a much better picture with the tube at a much better price. Samsung is the only one I know that sales the tube type and it is awesome. Best Buy carries the Samsung tube line in Tulsa. I paid less than $500 for my 27 inch.

I have a Samsung 27" and am getting a pretty awesome picture. Can't imagine much better. But, I guess I'm not understanding what you're saying. Is this tube different, or are you speaking of all tube type TV's as compared to LCD?

[patric]

quote:Originally posted by Wrinkle

It's that series connection UHF to VHF antenna that I think is messed up, not the multplexed cable from there down. I never quite understood the differences between 75-Ohm and 300-Ohm stuff, but the 300-Ohm (flat two-wire brown ribbon cable) on the UHF connects to the VHF with an adaptor with screws on one side and a coax connector on the other side (75-300 Ohm).

If I understand you, you're describing something that looks like this?


It's a passive splitter (or combiner if you have it at the antenna).  Being passive, It has no amplification and is very "lossy" (eats up a lot of signal), and used when people have separate UHF and VHF antennas but dont want to run separate coax downstairs for each (the better option).  They connect the antennas in Parallel using a  resistor/capacitor network to match each's impedance.  About $2.

quote:Oddly, the new HD satellite (D10) will require un-multiplexing the coax to receive local channels since the Local Satellite HD will overlap the multiplexed UHF/VHF signal, as I understand things.

IOW, separate run all the way to receiver for OTA UHF/VHF.

Sounds like you've already figured your best bet is a separate coax for each antenna, which is one reason why many people opt for combination UHF/VHF antennas that are one antenna (with one coax connection) that have elements for both UHF and VHF.

[Wrinkle]

Yeah, my UHF to VHF connector looks similar to the one you show.

Since the UHF antenna has the Twinlead wire (flat brown ribbon), seems one of these adaptors will always be required to convert to coax, right? So, should one consider an amplified one there due to loss you state?

I guess I'll run a dedicated UHF coax down to the receiver, parallel to the DirecTV coax, and all in R6 coax. As I understand things, everything available on VHF is now duplicated on UHF or UHF HD at this point, so if I drop the VHF altogether, no loss, right?
At least, if I have an ATSC receiver like the H20.

[patric]

quote:Originally posted by Wrinkle

Since the UHF antenna has the Twinlead wire (flat brown ribbon), seems one of these adaptors will always be required to convert to coax, right? So, should one consider an amplified one there due to loss you state?

If it's not too inconvenient, try it without an amplifier first, just to see.

At the antenna, you need to convert the older-style flat (300 Ohm) to Coax (75 Ohm) with a Matching Transformer (sometimes called a Balun).
Looks like this:

Newer antennas dont need these, and connect directly to coax. You will want to waterproof this part once you install it; silicone caulk works best.

Sometimes, just that will be enough for one TV unless you have a really long cable run, but if you find later you need some amplification the best place to do it is at the antenna.
Here is one Radio Shack sells.  The cylinder is the amplifier that screws into your RG-6 coax at the antenna, while the rectangular box is it's power supply that plugs in downstairs near your TV.

quote:I guess I'll run a dedicated UHF coax down to the receiver, parallel to the DirecTV coax, and all in R6 coax. As I understand things, everything available on VHF is now duplicated on UHF or UHF HD at this point, so if I drop the VHF altogether, no loss, right?

Its both UHF and VHF.  For instance, KTUL-DT is on VHF channel 10, but has to limit their signal (for now) to keep from interfering with other cities that currently broadcast on Ch. 10 until the switchover.

Here's the Tulsa lineup:

NBC   56   KJRH-DT
CBS   55   KOTV-DT
FOX   22   KOKI-DT
ABC   10   KTUL-DT
PBS    38   KOED-DT
UPN   42   KTFO-DT
IND   49   KGEB-DT
IND   48   KWHB-DT
WB   55-2   KWBT-DT
PAX   28   KTPX-DT