HDTV Forum

Strange question:

I have an HD receiver (from VirginMedia in the UK)

I am going to buy an HD Television.

I know this sounds nuts, but what would happen if I connected them with the normal analogue coax cable?

The signal has to change to analogue at the last minute anyway (within the TV) so would making this change at the stage before make a difference?

I know the difference would be minimal with audio - what about an HD video signal? Can the coax cable handle it anyway? Would my box downgrade the signal to the coax output anyway?

Thanks

If you connect a coax from your HD tuner to your new HDTV - why? To connect a coax to a HDTV means most likely that your HDTV has a HD tuner built in. To get HD to your HDTV, all you need is a good antenna connected by coax to your HD tuner in your HDTV. I have used this connection in my HDTV for almost a year, using a 30 year old antenna in my attic. Free HD looks great.
The only other way to get HD in your new TV is by using a cable or satellite service and connect to your HDTV by a component or HDMI connection. Last week I had Verizon FIOS hook me up with HD over their fiber optic network. I wanted ESPN and other sports in HD -- WOW! Well.....there is one other way that I am using to get HD. I have a HD tuner in my PC in my office and I record HD over-the-air to the hard drive. I also have another PC's video connected to the DVI connection in my HDTV. I can play back the recorded HD over my home network in full widescreen as clear as the original broadcast. Another WOW!
OneNetTech

To answer the question - the only way your HDTV can receive a HDTV signal over coax is via ATSC (usually with an OTA antenna). This means your HD Receiver would have to receive the HD signal (I assume via digital cable) and retransmit it over the coax as an ATSC signal on a specific UHF or VHF channel. No such feature exists on any HD receiver AFAIK.

Thanks - I thought as much. I wonder how good/bad it would look if it were possible. I bet it would look pretty much as good as going digitally.

Assuming it used the full bandwidth of the coax, it would look just as good as the original picture in the HD receiver - no better, no worse. I think you're confused about coax though. In this case you'd be sending a digital signal on the coax just like the digital ATSC signal you get OTA.

Unless you're talking about component video which uses 3 coax but is video only - no audio.

Sicone,

I believe your question requires a little more of "why I want to do that", and the responses could then be more specific to your need.

The function of any external tuner box (cable or otherwise) is to tune and convert the signal to a number of outputs to allow connectivity (and resolution matching) without having to retune again at the other end, the TV.

When HD is tuned by the box it is usually sent as HD to component analog, BNC, VGA D-sub 15, HDMI or DVI. And to coax as SD analog, to connect to a regular TV tuning channel 3 or 4 for backward compatibility with millions of legacy TVs.

In other words, the tuned HD signal is downconverted to about 9 times its resolution (quality of NTSC 480x450, from 1080x1920 HD), converted to analog, radio frequency re-tuned to channel 3 or 4, sent out via the coax, and the TV is expected to tune with RF to that channel 3 or 4 to get the signal out of that analog carrier, take the video and audio out of it, and process for display and sound, regarless if that display is analog or digital TV.

On the HDTV end, to receive HD from an external tuner box (cable or otherwise) the TV has to have component analog, BNC, VGA D-sub 15, HDMI or DVI. The TV is not tuning anything in that case, the tuner box does.

If you connect the coax from that tuner box to the TV, regargless that the coax is perfectly capable to handle a high-bandwidth HD signal (remember it comes that way from the cable company to your home with dozens of other HD channels within the same coax), you will not get a bad signal but it will only be SD analog, which certainly would not as good as HD, but is expected to be better than the old analog NTSC/QAM channel because it was transmitted digitally.

The TV in turn would upconvert that SD analog signal to its native 720P or 1080p for display adding thousands of calculated pixels (way over 1.5 million in the case of 1080p TV), but all the newer pixels and lines are just calculated by the internal video processor to fill the image, they were not obtained from the original signal (which HD quality was already severed on the tuner box when downgrading 9 times to NTSC for that kind of coax output).

Regarding OTA (ATSC over the air) tuning via UHF/VHF antenna, you can use the coax input specified as DTV on the back of your TV and its internal tuner would do the tuning in digital to that particular channel (not just 3 or 4 as when coming from the cable box in analog).

No external box is needed for that type of tuning, and the service is free. If the TV has a CableCARD or in-the-clear QAM cable tuner, it will do a similar job from a coax coming from the wall with the digital cable signal, but that is not what you asked.

In other words, the cable TV box does not output over its coax an ATSC version of the tuned cable HD channel, for the TV to tune in HD from it.

Best Regards,

Rodolfo La Maestra

we live in a rural area, no cable. current antenna for ota analog recieves about 15 stations, some really good, others snowy but watchable. We want to upgrade to a hdtv for movies and games. Will our reception via analog be about the same as with our old analog tv?

"Will our reception via analog be about the same as with our old analog tv?"

Most likely the analog display will be about the same (only bigger). When you get a HDTV get one with an ATSC (HD) and a NTSC (Analog) tuner. Since you have a lot of stations that have a good signal, you may be able to get OTA HD, depending where the transmitters are located.
My HDTV receives both HD and Analog on one coax connection from the antenna in the attic to the TV.
You could opt for a satellite service if you

thanks 1net - did I mention we are restraining ourselves from going satelite until the kids are out of the house? (two years, 4 months, 10 days...) Hard enough getting them to do homework.

btw, we get so many channels because we are within 40 miles of Vancouver BC. I realize they follow different regs, but today I noticed the black bands on some of their broadcasts which I assume means that some are already broadcasting HD. thanks again for the quick feedback.

Great Forum!

Remember that the local stations use different channels to broadcast their DTV signals so your reception will vary depending on the channel, tower location (may or may not be the same as the analog channel) and transmitter power. e.g. in Atlanta our local channel 2 use channel 37 (or 39 - I forget) for their DTV signal. When they cease analog in 2009 I think it's up to the station which channel they continue to use for DTV.

Also - you don't need a NTSC tuner in your TV. Just use an old VCR if you need to tune in NTSC channels.