Maximum transmitter angular difference for OTA TV reception

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Old 12-12-14, 05:11 PM
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Maximum transmitter angular difference for OTA TV reception

What is the widest angle between transmitters my stone-aged TV antenna is liable to be able to cope with?



I ask because when I first connected it (this morning), I was able to get stations with transmission towers as far apart as 30. Then I did some rearranging (including re-aiming the antenna) because the image on a couple of the stations was pixelated, and they intermittently were cutting out (losing 'capture'?). And my boy scout compass told me the antenna was pointed too far south, so I turned it north to sort of split the difference. Before I waste my time running up and down the ladder to the roof incrementally tweaking the antenna, I thought I'd ask here if there's even any point.

Back in the analog days, we got all the stations at once, but like I say, that was in the analog days. This is my first experience with broadcast digital.


If that is too broad a span, is it possible to add extra jury-rigged elements (from one of those YouTube D-I-Y videos) to the same mast, pointed in a different direction from the main antenna, then combine the signals?
 
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Old 12-12-14, 05:42 PM
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I think this antenna could probably just go away - if you look at the design of OTA digital antennas, you'll notice how much smaller they are. For best performance, the size of the elements should be optimized to match the wavelength of the signals being received.

You can do multiple antennas for different directions, you'll either need an appropriate switcher to switch the TV input between the different antennas, an an antenna combiner (aka antenna joiner), that you can feed to multiple lines into, and spit out one signal for the TV.

Or get one with a rotator so you can re-aim the antenna from the ground, as required for different stations... something like this: http://overtheair.saveandreplay.com/OTA_Products.asp
 
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Old 12-12-14, 05:56 PM
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The single biggest problem with HD signals is that they are transmitted with very low power. Aim is critical to reception as well as height. You could raise or lower the antenna a foot and get all the stations.

I live a stones throw from NY city. There is a mountain range between me and the city. When the signals came from the Twin Towers I could get reception with rabbit ears. Now the signals are coming from the Empire State building. I get very sporadic reception and I have a large beam on the roof. I'm hoping now that the new Tower is up... the stations will move back.

I do get several stations from around NJ crystal clear but they are shopping and religious channels.
 
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Old 12-12-14, 06:27 PM
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That antenna has a fair number of elements. Generally, the more elements the better the reception of distant stations. The trade off is a narrower reception "width". To get the best results, you will need a rotor. Just F.Y.I., since most stations these days are on the uhf frequencies, most of the reception work is being done by the front portion of your antenna.
 
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Old 12-13-14, 01:50 AM
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As stated most of the new digital stations are on UHF and they are definitely worse for reception over longer distances than the VHF stations. Yes, about 30[SUP]o[/SUP] is the maximum angle to get a useable signal, especially with UHF digital. Wind and rain also will decrease the signal, more so on the UHF channels as will almost anything (read tree branches and leaves) between the antenna and the transmitter.

Both horizontal and vertical positioning is important. If I move my antenna closer to the house I lose channels and since my mast was bent during the windstorm of Thursday night I have lowered the antenna about three feet and totally lost the local PBS station.
 
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Old 12-15-14, 06:01 PM
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Sunday I re-aimed the antenna far enough south to confirm it will not get decent signal from ABC (in the south) and any other station simultaneously. So I'm definitely in for an added VHF element.

There's still two mystery stations I have yet to find. Antennapoint says one, the PBS affiliate, is exactly co-located with the ABC tower (same tower?) but is a very low-powered signal. so that one might be a lost cause.

The real mystery is the other one, the NBC affiliate. It's about 12 north of the ABC/PBS tower, and 18 south of CBS, so the antenna swept past it going from CBS to ABC, but there wasn't a glimmer of it. It isn't massively powerful, ~50 kW, but it has substantially more horsepower than the PBS station. I'm thinking it could be it's going to require an antenna with elements tuned specifically to its frequency, and aimed very precisely, to bring it in.

Being as it's a VHF station, would a tapered loop antenna be a better choice than a bowtie? And if yes, is it possible to D-I-Y a tapered loop? I ask because I haven't seen such a design on offer in my searches.
 
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Old 12-15-14, 09:27 PM
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A modified Yagi is best for VHF stations. Neither of the other two antennas are very good with VHF.

In my case I have to elevate my antenna to pick up the PBS (VHF) station. We has a moderate windstorm last week and it bent my mast among other things so I lowered the antenna to about ten feet above the ground and it is pointing a bit towards the ground because of the bent mast. I can still receive all my other stations reasonably well but I cannot even find the PBS station. All from lowering the antenna about four feet.
 
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Old 12-16-14, 05:23 AM
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Make sure it is a VHF station and not a "virtual" channel that is actually transmitting in the much higher UHF bands.

TV stations have spent the past 70 years developing their brands as Channel 2, Action 4 News, etc. They maintain this branding by remapping and virtualizing the channel plan. When you press 7.1 on your remote, the TV could actually be tuning to a UHF frequency. Check Antennaweb.

In the digital world reflections cause issues. Two antennas aimed in different directions can receive the same signal at different times. The delay can adversely affect picture quality.

You can, but shouldn't, combine two or more antennas unless you plan to also install bandpass and channel elimination filters so they don't interfere with each other. This can get really complicated and really expensive in a hurry. It's much more economical to install a rotor.
 
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Old 12-16-14, 05:30 AM
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By the way, I got rid of the old VHF/UHF mast and made a coat hanger antenna like the one in the photo below. Mine has 2x the elements and picks up stations as far away as 33 miles. It is in the attic about 18 feet above grade.

[ATTACH=CONFIG]43319[/ATTACH]
Photo courtesy Combobulate com
 
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Old 12-16-14, 03:42 PM
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Rick, thanks for the advice about the virtual stations. Turens out the ABC usin

Rick, thanks for the virtual channel tip. The NBC (which I don't get a glimmer of) and CBS affiliates are on virtual channels, but their actual channel still is VHF (<14). PBS (which I also see no sign of) is the only one with a virtual channel matching its original VFH channel. ABC's actual channel is UHF but its virtual channel is VHF.

So of the four, I don't see squat of two. Both are transmitting on VHF.

NBC (which is AWOL) is 15% further away than CBS (which is 5x5) but transmits with 4x as much power. So go figure.

I hate the thought of resorting to a rotor because that will mean one family member gets to control which stations are available. Could get ugly. I hadn't counted on gunplay when I ditched the dish.
 
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Old 12-16-14, 07:42 PM
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Hey All,

I've cut the cord with all pay TV and have been happy with what I've done. I have spent a few hundred dollars on antennas and rotators tho', and now I've run across an antenna with built in rotator and adjustable amplifier up to 36 db in UHF and 32 db in VHF. No need to run new coax if you have existing because the rotator and amplifier power goes through the cable. This all just sounds wonderful. I'm sure that if you have splitters between where you're going to power this system and the antenna, you'll need to replace them with ones that will pass power to the amp and rotator. It's made by Lava and supposed to be good for 150 miles. I think the model is #2650.

I'm thinking of buying one and am wondering if anyone has tried this system? It's very reasonably priced, far less than I've payed for individual components.

Curious,
Lonnie
 
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Old 12-16-14, 07:49 PM
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I've worked with similar antennas that were only functional for short distances. Not the exceptional distances that were advertised.

That Lava looks to be in about the same class. I wouldn't expect too much for $50.
I think you meant the #2605.
hdtv-antenna-review.top ten reviews/lava-hd2605-review.html
 
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Old 12-16-14, 08:55 PM
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I agree PJmax, that's why I asked. Like I said, I've spent some bucks on antennas, rotators and amps. All do what they claim to do but the antenna. Since most stations have gone UHF, it's hard to receive them unless you are close. I was just curious if someone had tried this antenna. It sounds great for the price.

What I have is working where I am now. It took some tuning and tweeking but, it's doing fine and I've just gotten a new station that I like a lot. "Grit" is great!
 
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Old 12-24-14, 03:50 PM
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Would I be doing myself any favors as concerns picking up the missing channels or spanning the angular difference between the stations if I bought a new antenna? And if so, what (cost-conscious) design or model would you recommend?
 
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