Digital Antennas (1998)

Discussion in 'Free To Air (FTA) Discussion' started by JosephHolloway1998, Jul 29, 2019.

  1. harshness

    harshness SatelliteGuys Master

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    Back when? TV antennas are TV antennas as has been pointed out many times. Some don't offer full TV band support but they're still TV antennas.

    "Digital" and "HD" were terms glued onto conventional TV antennas to try to generate excitement by suggesting that there was something new inside. In most cases, these were the same old same old that had the artwork on their packaging redone.

    In many cases, UHF-only antennas were marketed heavily as so many of the broadcast stations were UHF. That is changing.

    Channel Master makes several models of full-spectrum TV antennas as does RCA and Winegard. The key terms to look for are coverage of VHF, UHF and especially FM (at the top edge of the VHF-low band).

    Speaking of FM, think of Digital Antennas this way: The marketroids would have you believe that FM stereo requires a more advanced antenna than FM monaural. It doesn't but it certainly sounds important.
     
  2. Titanium

    Titanium AI6US Lifetime Supporter

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    Could someone also list all ice cream flavors available back then at Baskin and Robbins? Vanilla and chocolate flavors were commonly available as was black cherry.

    Were waffle cones a required purchase or could scoops be purchased in a standard cone or paper cup? Did ice creams melt as quickly as sherbert?
     
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  3. FTA4PA

    FTA4PA Satellite Guys Family Lifetime Supporter

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    :D
     
  4. JosephHolloway1998

    JosephHolloway1998 Topic Starter SatelliteGuys Pro

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    to add to that, the stations you receive generally depend on the height of the antenna.
     
    #64 JosephHolloway1998, Aug 26, 2019
    Last edited: Aug 26, 2019
  5. harshness

    harshness SatelliteGuys Master

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    That's a misrepresentation of the facts. Best reception depends pretty much entirely on coming as close as possible to Line-of-Sight (LOS). Height typically helps only if it clears more of the obstacles (man made and natural structures -- both flora and geological) between the broadcast antenna and your receive antenna.

    RF signals in and around the TV band don't "wrap" or bend around things nor do they pass through anything of substance very well. They may bounce and this may be to your advantage (or disadvantage in the case of multipath). This is in accordance with the laws of Physics that are, for all intents and purposes, immutable. As the frequencies get higher (such as with satellite frequencies), LOS becomes an imperative. LOS may be a little misleading because it doesn't include materials that are visually transparent.

    More height can actually hurt reception under some conditions (if it exposes your antenna to multiple channels or reflections of the same RF frequency).
     
  6. Titanium

    Titanium AI6US Lifetime Supporter

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    A high VHF mux at my home arrives over a blocking ridge by "knife edge". Raise the antenna above 10', the signal drops and the channels are lost.

    So much for the "laws of Physics"... :)

     
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  7. N6BY

    N6BY Geek Lifetime Supporter

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    Interesting -- they actually change direction downward due to the 'knife edge' effect. I hadn't heard of this before so I looked it up here: Knife-edge effect - Wikipedia

    So black holes aren't the only thing that can bend electromagnetic waves.
     
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  8. FTA4PA

    FTA4PA Satellite Guys Family Lifetime Supporter

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    Yep, this is how I get our channels from the Wilkes-Barre/Scranton market. There is a large hill between us and the signals 42 and 57 miles away. If our VHF and UHF antennas are pointed level the signal lowers or is lost completely on some channels. When I tilt them upward the signal comes in fine with only an occasional loss on the lowest power channel WSWB. Weird but it works so I'm not complaining! :rolleyes:
     
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  9. harshness

    harshness SatelliteGuys Master

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    This isn't limited to electromagnetic waves. It also works with sound waves and waves in liquids.
     
  10. N6BY

    N6BY Geek Lifetime Supporter

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    The 'knife edge' effect may also explain why I can get SF Bay Area TV stations from 100 miles away. The direct line of slight from my house to the Sutro Tower in San Francisco is blocked by the coast range.

    But I tend to receive them only at night, so maybe something else is going on.
     
  11. Comptech

    Comptech SatelliteGuys Pro

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    Ha ha, I had my VHF high propped up on my front porch, finally put it on a pole two weeks ago not 10 feet were it was but 20 foot higher and lost a bunch of signal. Have to move it again.
     
  12. FTA4PA

    FTA4PA Satellite Guys Family Lifetime Supporter

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    Sounds like tropospheric refraction which can improve reception of not too distant stations at night. Valleys and coastal areas benefit most from this and it can be regular phenomenon unlike tropospheric ducting which will allow reception of distant stations, sometimes 100's of miles away, for a brief time under the right atmospheric conditions. More about it here from a site which no longer exists except for the Wayback Machine. :)

    Tropospheric DX Modes
     
    #72 FTA4PA, Aug 27, 2019
    Last edited: Aug 27, 2019
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  13. Keith Brannen

    Keith Brannen SatelliteGuys Pro

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    Newer version here: Tropospheric DX Modes

    Same site as primestar31 mentioned earlier in the thread which has the Tropospheric Ducting Forecasts.

    A very interesting site.
     
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  14. JosephHolloway1998

    JosephHolloway1998 Topic Starter SatelliteGuys Pro

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    could a lightning arrestor protect UHF/VHF/TV Antennas (RCA, Winegard, Channel Master, Omni-directional antenna, Semi-directional antenna, Off-air antenna) from a lightning strike? many of the antennas could be affected by lightning, tornado or other weather conditions.
     
    #74 JosephHolloway1998, Sep 7, 2019
    Last edited: Sep 7, 2019
  15. Brct203

    Brct203 SatelliteGuys Pro

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    I don't think anything would really help in case of a direct hit, other than unplugging the equipment. I would think that OTA antennas that are mounted on the house are also not as likely to get energized by the dissipation in the ground of a nearby hit, compared to a large dish that is often planted in the ground at a distance from the house (creating a voltage differential with the house ground).

    In my opinion, the biggest threat to antennas is wind and maybe heavy sticky snow, but of course that's not a threat to the indoor equipment.

    when i was a kid, we had antennas about 6 meters above the roof, for a total height of about 16 meters (about 50 ft). The mast was kinda grounded. Back when it was first installed in the early 50's, the local electrician turned TV-specialist had installed a ground wire, but with an interruption of about 1 mm in one spot. The theory was that it would let lightning jump that gap but would avoid "ground interference" on the TV. And one morning in 1978 we got hit by lightning. The top antenna got significantly damaged, one of its reflectors was found in the neighbor's yard across the road. The lightning energy entered our electrical wiring through the antenna preamp and through our old TV (we had unplugged our brand-new color TV a few minutes before the strike). The damage was very strange... A few light bulbs looked intact from the outside but the glass "stem" that holds the filament was shattered. A few other bulbs had holes in them. Also a few random switches got shattered. and 2 of the 3 large service fuses at the service entrance got blown (we had 3-wire service as we had a workshop). Of course the old TV and the antenna preamp were dead. I don't think we had any other significant damage, but was was remarkable was mostly that the damage was very odd and seemingly unpredictable.
     
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  16. harshness

    harshness SatelliteGuys Master

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    No. A lightning arrestor will not protect the antenna nor anything connected to it from a lightning strike. "Lightning arrestor" is really a misnomer as they are designed to dissipate static charge (like the energy that makes your socks stick to your towels out of the dryer) rather than lightning bolts. Like socks in the clothes dryer, this static typically comes from wind blowing across the antenna.

    Lightning is like using a freight train as dental floss. The average lightning bolt is thought to be motivated by a voltage about 1-10 million times that of an automobile starter battery.

    It is perhaps easiest to think of lightning in this way: If the "bolt" has enough "motivation" (voltage) to arc across hundreds of feet of air (a widely recognized insulator), it isn't going to lose interest when presented with anything conducts better than air.
     
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  17. JosephHolloway1998

    JosephHolloway1998 Topic Starter SatelliteGuys Pro

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    well as with the long-range antennas for TV reception, how far do they go?
     
  18. harshness

    harshness SatelliteGuys Master

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    That depends on your surrounding terrain. With line-of-sight and an antenna that doesn't lie about its gain, expect 80 miles (on a good day). Without LOS, expect distances to go down quickly.

    Keep in mind that with long-range antennas, their "beamwidth" tends to be rather narrow and if you're not pointing at a distant station, you probably won't pick it up.

    As pointed out in another thread, tropo doesn't happen often on the Left Coast.

    Finally, since most RF channels are occupied in your area, give serious consideration to a full-range antenna (FM-VHF-UHF) that is as directional as possible if you're going to spend the big money. If the antenna doesn't advertise FM, it probably can't hope to capture VHF-low.
     
  19. navychop

    navychop Member of the Month - July 2014! Pub Member / Supporter Lifetime Supporter

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    I really think anything over 60 is lagniappe.


    Sent from my iPhone using SatelliteGuys App. For now.
     
  20. harshness

    harshness SatelliteGuys Master

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    Everything depends on the environment.

    The area south of the Grapevine is a somewhat hostile environment. I suppose we could toss in the rest of California as well.
     

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