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Pierrefonds, QC

2 edits
reply to leibold

Re: Hopeless or possible? HDTV OTA

said by cdru:

An antenna 30' off the ground has LOS to an antenna 85 miles away if the far antenna is approximately 3000' tall.

Considering the direction of the stations, as per tvfool.com, it seems to point at the adirondaks. I'm betting the transmitters are on top of the mountains. The website does say I have LOS and it does mention that other closer stations aren't in LOS, so I think they are correct.

edit: Yup, mountain top (all of them). Check these coordinates on google maps 44.525607 -72.815679 (according to some google API, that mountain top is 3000 feet up )

said by leibold:

That is the wrong antenna for long distance UHF only stations. Most of the receiving elements on that antenna are for VHF which won't do you any good at all. The fact that is also doubles as an FM radio antenna might even be harmful for your purpose.

What you need is a multi-element directional UHF antenna such as the 8 element Channel Master CM-4228HD or Winegard HD-8800.

Those multi-element antennas (if properly aligned) combine the weak signal from distant transmitters.

1 - There are a couple of local stations that are VHF-Hi that i'd like to get (I'd get a motor to orient it if I watch those channels). Though I guess i could get a second smaller cheaper antenna for the local stations.

2 - The far away stations are all in the exact same azimuth, wouldn't a yagi get more distance if perfectly aligned?

Sunnyvale, CA

The purpose of an antenna is not to "get distance". Its purpose is to get as much as possible of the transmitted signal while ignoring as much noise as possible.

I'm not an HF expert but I very much doubt that a single yagi antenna will get anywhere near the same amount of useful signal as these multi-element antennas.

The yagi while directional isn't as sensitive to direction and a slight deviation from optimal will probably still get you a good signal (provided it is strong or close). However in order to get the same gain as a multi-element UHF antenna you would have to combine several yagi antennas. This is not easy but it is possible and if you search on the Internet (look for vertical and horizontal stacking of antennas) there are reports from people who have done that. If you do that you have the same gains but also the same requirement for proper alignment as with a multi-element antenna.

The multi-element antenna is more challenging. Any deviation from the correct alignment will cause the signal to arrive phase shifted on some of the dipoles. That phase shift will cause the signals to partially cancel each other out (instead of the signals being combined to a much stronger signal).
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