Outdoor Antenna Performace Calcs

Discussion in 'Tuners' started by Whitehall, Jan 20, 2006.

  1. Whitehall

    Whitehall Super Member

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    Location:
    Silicon Valley, CA
    Outdoor Antenna Performance Calcs

    Mr. Beezley has a site with extensive FM circuit and antenna information ( http://users.tns.net/~bb ). He's modeled a number of commercial and special construction FM antennas and has provided detailed comparison of the relative performances.

    I've borrowed two of his performance charts and attached them for AKers.

    The first one is for forward gain of the antenna - how much boost does it give a signal in the direction it's pointing over the standard dipole. This is a figure of merit that is simple to understand - the higher the gain, the stronger the signal at your tuner. The horizontal axis is frequency with 88 MHz on the left increasing to 108 MHz on the right.

    The second is the front-to-back ratio over the same frequency band but using the worst case since antennas have back lobes that aren't always directly behind the pointed direction. This is important for the antenna's ability to reject multipath signals. Again, the higher the better. Both vertical scales are in dB.

    For both charts, special-built antennae outperform commercially available units. They are special built because there is no market at the price points necessary to cover the construction and shipping costs.

    More useful are the comparisons of the APS-13 and the Winegard HD6065P. Also on the charts is the Channel Master Probe 9 but it's no longer mentioned on their website so one can assume it is no longer offered although one might come across a NOS unit.

    My reading of the charts is that frontal gain of the APS-13 is just a little better than the Winegard - maybe 1 dB over the band. Where the APS-13 shines is in front-to-back rejection - there it is 10 to 18 dB better, depending on frequency. If you're in a valley or a city with lots of multipath reflections, this might make it worth the 2.5X price difference.
     

    Attached Files:

  2. OvenMaster

    OvenMaster Pompous Windbag Subscriber

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    What a magnificent site, Whitehall!! Thank you for that!:thmbsp: I'll be bookmarking and studying THIS one for sure!
    Tom
     
  3. Phil H

    Phil H Active Member

    Messages:
    353
    Thanks Whitehall,
    This will help me decide what antenna to get. (right now I am playing around with the inexpensive Radio Shack antenna) I wish he included the APS-9B in the chart. I live in an area with extreme multipath. I don't want to to deal with the the 200" long APS-13. But, the APS website says the APS-9B f/b ratio of 28.8dB compared to the APS-12's 30dB. I was considering the HD6065P. It looks like I will be better of spending the extra money for the APS-9B with a much better f/b ratio.
     
  4. EddyR

    EddyR Well-Known Member

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    682
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    I could not get the link to work.Is it still working?
    Ed
     
  5. hifi_nut

    hifi_nut Vintage? I´m vintage!

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    Neither could I, and I´m really interested.
    Jorge
     
  6. theodoric

    theodoric 101° Rx = + /_\

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    http://users.tns.net/~bb/

    You have to take the trailing parenthesis off the path.
     
  7. hifi_nut

    hifi_nut Vintage? I´m vintage!

    Messages:
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    Whitehall - What a great link. Forever grateful.

    Theodoric - Thanks for helping out a middle aged bumb ass.

    Jorge
     
  8. Whitehall

    Whitehall Super Member

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    Please note that I used the word "calc" in the title. Antenna design and analysis is not a completely nailed down technology. Even test methods are a bit sketchy I understand and may not really be applicable to your situation.

    Bottom line is that you should treat these numbers as a best guess. Also they are for right-cicular polarized transmissions only. Beezley claims that almost all commercial FM stations use that form. Maybe he's correct.

    Did anyone checkout the homebuilt that looked like a piece of DNA? It's made from PVC and refrigerator tubing - high gain and great f/b. Your house would like Dr. Frankenstein's castle with that on your roof.
     
  9. Whitehall

    Whitehall Super Member

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    2,157
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    Omagosh! I just realized that I misspelled "performance" in the thread title.
     
  10. 4yanx

    4yanx Active Member

    Messages:
    159
    Anyone more experienced than me (re: anyone), want to take a general stab at picking the best ones given particular applications?
     
  11. Whitehall

    Whitehall Super Member

    Messages:
    2,157
    Location:
    Silicon Valley, CA
    For commercial units, ranking the top three in terms of price-to-performance (total installed price) it would have to be:

    1) APS-13 $215 but at 200 inches long, more support strength and room needed

    2) Winegard HD6065 - at $85 and 120 inches long, a reasonable compromise - this is the one I have

    3) APS-9B - $100 and 100 inches long - maybe a bit better than the Winegard in high multipath areas and shorter but more expensive and a tad off the Winegard in straight-ahead gain.

    So the absolute top-of-the-line commercial FM antenna rig is an APS-13, a rotator and stout mounting hardware, Belden RG-6 cable, and a GaAs FET signal amp.

    Antenna $215
    Mounting Hardware $100 (ballpark)
    Rotator $80
    RG-6 cable $60
    GaAsFET signal amp - $160

    Total - $615 (more or less)

    The question then becomes, where do you put your money - antenna or tuner?
     
  12. onepixel

    onepixel .

    Messages:
    32,015
    Thanks Whitehall. I was considering getting an antenna. All the tat technical stuff is over my head. I'm going to have to do some homework.

    I have a question, would I be able to hook my out door TV antenna to bring in FM?
     
  13. CarlV

    CarlV AK Subscriber Subscriber

    Messages:
    22,360
    Location:
    SF east bay
    Yes, FM is between channels 6 and 7 IIRC.

    Here is a thread I started when I was picking out an antenna.
    I am very happy with my APS-9 with Channel Master rotor. :)


    Carl
     
  14. CruzBay

    CruzBay Well-Known Member

    Messages:
    582
    Location:
    Springfield, VA
    I've got a few frequency specific antennas that where I work that were used to set up a primitive cable TV system, would it be worthwhile to grab the Yagi that pulled in channel 7 and use this one? Might the antenna be too frequency specific and reject FM? Missapplication of a Yagi?

    I'm going to be in Spotsylvania county, Virginia, using an MR-78.

    Speculation is fine; I'm getting the antenna(s) for free. If a new thread's called for, let me know, or PM me.

    Thanks!

    Mike
     
    Last edited: Aug 17, 2006
  15. Harvey/ Ga

    Harvey/ Ga AK Subscriber Subscriber

    Messages:
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    Location:
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    I have a large, multi-element TV antenna on the roof...7 angled VHF elements and probably an equal number of UHF elements with multi-elements in a Vee above and below.

    My question is whether to just strip the co-ax coming from it and attach it to my CR-820 or the SX-3800 or get a band splitter from Radio Shack that will separate the FM signal from the TV signal (and probably convert it to 300 ohms)
     
  16. Whitehall

    Whitehall Super Member

    Messages:
    2,157
    Location:
    Silicon Valley, CA
    Mike,

    Breezley has a yagi example that is spec'ed just for the lower FM band - 88 to 92 MHz. Yagis are generally not big enough for the whole FM band so a channel 7 yagi would probably not work very well. One TV channel has the same bandwidth as the whole US FM bandwith allotment.

    Harvey,

    Most tuners have a bandpass front end that rejects most frequencies outside the FM band so bringing in a wide bandwidth TV antenna signal might work. However, if RadioShack sells a bandpass filter, it is probably for a good reason. I'd play it safe if the filter is not big bucks and install it if on the roof. If at the tuner, I'd see how it works without it first. If you're next to a TV transmitter or other high energy RF source, then it might make a difference.

    Also, some TV antenna manufacturers filter out FM at the antenna so not all TV 'tenas will deliver an FM signal.
     
  17. Tullman

    Tullman Well-Known Member

    Messages:
    565
    I live in the city and I have an APS13 which performs very well.

    I had mine professionally installed. The total was about $600. I don't think you will need the signal amp.

    I know $600. is a lot of money but the benefits are huge. This was a very worthwhile investment. If you have a house and can mount an antenna, go for it.
     
  18. Jygesq

    Jygesq Well-Known Member

    Messages:
    600
    without a good outside antenna best tuner will

    not perform better . Spend the money on the antenna. I also have the winegard , its great..
     
  19. outlawmws

    outlawmws On the Run

    Messages:
    4,779
    Location:
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    I'm curious, how do the Radio shack FM antenna's stack up in such a test? Is it a knock-off of one of the tested ones?
     
  20. jcmusic

    jcmusic Well-Known Member

    Messages:
    624
    Location:
    New Orleans, La.
    What is that noise I hear when I have a very strong signal, sounds like static? Is this multipath, how do I get rid of it?

    Jay
     

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