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  1. #1
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    Default Excellent link with antenna comparisons with spectrum analyzer

    Nice shootout between several commercial antennas! Very interesting results!

    HDTV Antenna Comparisons

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    That is fantastic IDRICK! Thanks for sharing. Of note, the real world tests are different than the computer models at the HDTVprimer....which have the Winegard HD 8800 killing everthing on lower UHF Net Gain.

    I have the HD 4400 and it is unimpressive against the old CM 4221 and especially the AntennaCraft G1483...not to mention the Kosmic SuperQuad which beats all those handily.

    Computer models will only get you so far. NEC2 optimization isnt the last word in antennas, nor is NEC4. Optimizing antennas to those models will produce good results however they arent the ultimate arbiter of antennas.

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    EV, I agree, fascinating data that clearly demonstrates real world data is needed, rather than strictly modeling data. I thought it was interesting that the old and new DB-8's were essentially similar and that XG-91 won across the range when compared to the Winegard 8800. Nist's modeling suggests advantages for the 8800 with UHF channels 14 to ~35.

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    Interesting, for certain. And if anyone's wondering, the listed channels would imply the location for the testing was in the Reno market.

    - Trip
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    Comments are my own and not that of the FCC (my employer) or anyone else.

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  5. #5

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    Great post. It's funny how such different antenna designs get pretty close to the same performance. I'd like to see the same setup done on another spectrum analyzer, or are all spectrum analyzer's pretty accurate?

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    There probably are differences between spectrum analyzers that would result in somewhat different results. The original author stated that he is only making relative comparisons though... IMO, We need more independent testing under a variety of settings plus testing of the urban and mid range antennas.

  7. #7

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    Quote Originally Posted by IDRick View Post
    Nist's modeling suggests advantages for the 8800 with UHF channels 14 to ~35.
    Yes, I feel Nists modeling on both the 91-XG/8800 & the YA-1713 don't hold true under real world conditions. The 91-XG is a stellar performer on the lower UHF channels, & the channel 13 deficiency noted on the YA-1713 is unfounded.

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    Default Spectrum analyzer calibration

    Quote Originally Posted by IDRick View Post
    There probably are differences between spectrum analyzers that would result in somewhat different results. The original author stated that he is only making relative comparisons though... IMO, We need more independent testing under a variety of settings plus testing of the urban and mid range antennas.
    Spectrum analyzers need to be calibrated to a certain standard, and the use of that standard assures that calibrated analyzers from different manufacturers are as accurate as the next one up to the allowed tolerance of the standard itself.

    Age and heat cycles can change the characteristics of electronic devices over time, and this factor makes calibration on a given time frame a must in order to ensure the continued accuracy of that device. In some instances, depending on its use, the FCC requires calibration, and certification of the calibration in order for it to be used in a "Proof of Performance" test of a TV, or other type of FCC regulated transmitter such as an FM transmitter.

    A "Proof of Performance" diagnosis of a TV transmitter is normally done on a somewhat regular basis in order to ensure compliance with FCC regulations, and to ensure that you are within FCC specs, and not causing interference with other broadcasters.

    This is much more important than it was with analog, since adjacent channels are sometimes used in the same market, and the devices used to do this testing must be calibrated and certified by the calibration service as complying with a given standard that relates to its intended use.
    Last edited by FOX TV; 12-01-2009 at 06:56 PM.
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  9. #9

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    I read somewhere on that site that his analyzer is old and doesn't have a current cal sticker. To me that says we just can't count on his absolute levels being dead on accurate. He's doing relative measurements though so that shouldn't matter too much. I'd expect most of the error would be due to antenna placement & pointing, connecting & re-connecting cables and natural signal variation in the off-air signal environment rather than errors in the analyzer itself.

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    Quote Originally Posted by No Static At All View Post
    Yes, I feel Nists modeling on.... the channel 13 deficiency noted on the YA-1713 is unfounded.
    I agree completely. I have a pair of YA-1713's stacked vertically by 40 inches for what I found by experimentation for the middle of the band.

    I have them aimed at Jacksonville, FL, at 61 miles. There is a 7, 10 and 13, nearly perfect to see the antenna across the band. My stacked array clearly works very very well on Channel 13.

    I never bought into Nist's arguement and would have to re-read his comments where I think he eludes he is not sure it's true (guess I or someone could look again).

    But the point is traditional TV antenna design and used on both the YA1713 and the Y10-7-13 is to make the directors tuned to the highest channel and the reflector tuned to the lowest channel. Then use either a log type feed (Winegard) or a folded dipole (AntennaCraft) to match across the band.

    Hence from my experience playing with yagis on 10, 2 and 1.25 meter ham bands the reflector bigger than needed has only a small effect, but the directors length are more critical. So with that, then either antenna should preform very well on Channel 13, Winegard or AntennaCraft.

    If you have not followed my trials and tribulations with stacking my YA-1713s a quick thumbnail of my trials. First, no test equipment except a receiver.

    Tried 60 inches, not any difference from a single yagi. Then 50 inches, very slightly better, but not worth the trouble. 40 inches, WOW! Signals that I only saw during strong band openings from Jacksonville (61 miles and 2 edge) suddenly where there 90% of the time (actually most of the time but killed by co-channel off the back from Tampa).

    I asked Hans at Winegard what he thought and he said 42 inches was the center of the band for his antennas. So I was very close by experimenting.

    As an aside, I also have a channel 9 (WNBW) that is LOS. I only see a slight increase in gain toward it. But the 2 edge signals from Jacksonville I see a tremendous increase in signal. I can't measure it, but it goes from 15 to 25 on my quality meter to 50 between one antenna and the two.

    I guessed at this because years ago I played a lot on 2 meter SSB which uses horizontally polarized antennas. The stations with vertically stacked yagis out performed other stations even when they were 100 miles away and only 20 ft in the air. I believe it's akin to pointing a UHF at a close by knife edge hill by maximizing reception where it's needed for VHF, right at the horizon.

    I knew those hams that stacked them were on to something. As their signals from 20 to 30 ft off the ground were as strong or stronger than those with a single long boom yagi up twice as high.
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    Quote Originally Posted by FOX TV View Post
    Spectrum analyzers need to be calibrated to a certain standard, and the use of that standard assures that calibrated analyzers from different manufacturers are as accurate as the next one up to the allowed tolerance of the standard itself.

    Quote Originally Posted by JER View Post
    I read somewhere on that site that his analyzer is old and doesn't have a current cal sticker. To me that says we just can't count on his absolute levels being dead on accurate. He's doing relative measurements though so that shouldn't matter too much. I'd expect most of the error would be due to antenna placement & pointing, connecting & re-connecting cables and natural signal variation in the off-air signal environment rather than errors in the analyzer itself.
    I agree that you need a calibration sticker to give calibrated results.

    However a calibration sticker is a comparison itself to a calibrated source.

    Thus if you use the same meter to compare two antennas you are doing the same thing and the results are accurate.

    One antenna becomes the calibrated source, then the second antenna becomes the measured quantity.

    So yes, I agree this doesn't mean you can say his results show antenna A to have exactly x amount of db on a given channel. But it will show which antenna is stronger.

    So yes, you can't be sure without calibration how much better or worse one is against the other, but still it will show a relative difference across the two antennas.

    So I don't consider the fact and he admits it's not calibrated to be any way a reason to discount or consider his work moot.
    The more I understand, the less I know.

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    Quote Originally Posted by IDRick View Post
    EV, I agree, fascinating data that clearly demonstrates real world data is needed, rather than strictly modeling data. I thought it was interesting that the old and new DB-8's were essentially similar and that XG-91 won across the range when compared to the Winegard 8800. Nist's modeling suggests advantages for the 8800 with UHF channels 14 to ~35.
    Well this is some evidence that my input without test equipment and the suggestions of Cowboy on using a YA-1713 with an XG91 as being the best systems a great deal of credence.

    A few known conflicting data to Nist (though I love his work, so Ken if you read this thank you for your work and publishing) are the YA-1713 and the 7698P. I know numerous people that have used both antennas without finding the weak bandwidth of limitation of some channels Ken's modeling suggests.

    This goes back to reading about early modeling software in the 1980s, though I am sure current modeling software if far superior but the same thing holds true about an antenna. The early users of computer modeling all said you often had to "tweak" the computer model to get it optimized in the real word.

    It still comes down doing real world tests.
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    I heard someone claim stacked Winegard 6000s were better than the AntennaCraft FM6. The 6000s have half the boomlength, about 1/4 wave at FM frequencies, of the FM-6 which is about 1/2 wave. These are properly distanced of course.

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    There are some more potential fantastic spectrum analyzer shootouts on the horizon....from the same fellow that brought you the ones in the post by IDRick!

    Check out the pregame planning here. About halfway down page 2... tballister, the AntennaHacks website guru....joins the discussion.

  15. #15

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    Hello All:

    I'd just like to say thank you to those who did read the caveats about the HP8590B Spectrum Analyzer being used, who understood the significance of being calibrated or not, and who expanded on the relevance of precise calibration.

    Sigh. I guess I should revisit my own remarks and try to do a better job, or move those caveats up front in bolder letters.

    I've tried carefully on the site to indicate that nothing presented intends to state any absolute signal levels. To the contrary all presentations indicate relative results.

    Its a little bit like buying the cheapest Radio Shack (no offense) Volt-Ohm Meter and asking the question "Which of these two batteries has a higher voltage?". You don't care what the voltage is, you just wanna see if the meter will move higher for one than the other. The only requirement is that the instrument has enough resolution to let you see the differences your interested in.

    To FOX TV and others who discuss "Proof of Performance" and related calibration-critical concepts: You are absolutely right and I agree with most everything you said. I held an FCC Radio Telephone First Class License for many years, and am still involved in broadcasting. So I like to think I'm pretty sensitive to the activity you are discussing.

    But to be clear, the "Proof of Performance" activity is precisely what I've tried to be clear I am not engaging in, claiming I'm engaging in, or intending to be engaging in.

    I just wanted to know which battery had more juice in it ... :-)

    Best Wishes,
    t
    Last edited by tballister; 12-28-2009 at 10:20 AM.

  16. #16
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    Quote Originally Posted by tballister View Post
    Hello All:

    ........ts a little bit like buying the cheapest Radio Shack (no offense) Volt-Ohm Meter and asking the question "Which of these two batteries has a higher voltage?". You don't care what the voltage is, you just wanna see if the meter will move higher for one than the other. The only requirement is that the instrument has enough resolution to let you see the differences your interested in........

    .......I just wanted to know which battery had more juice in it ... :-)

    Best Wishes,
    t

    Welcome to the forum.

    What a great website. I really love what you did on the Y10-7-13's reflector. I commented and you probably read I had a 2 meter Cushcraft "Boomer" series that had 3 reflectors, one in the plane then one above and below it slightly more to the rear (if mounted for horizontal polarization).

    I have a pair of YA-1713's stacked 40 inches vertically. It works well for my stations out of Jax (probably read all about this) but Tampa has the same stations about 20 degrees off the rear of my stack and they eat up Jax during tropo. Funny that at one point remembering my old Cushcraft 2 meter beams I thought about that for my stack and was elated you actually did it.

    As far as relative measurements I completely understood your point. I can't afford a calibrated SA ether and even used to own a nice one, but they are just too expensive or were to keep around for the occasional measurement. So I am plenty happy to read about your relative observations.

    A story of my own. Back in the day, being a poor college student I could not afford a power meter or swr bridge. I rebuilt stuff out of the 50's in the 70's to use on the ham bands. Someone gave me a cheap Radio Shack SWR meter meant for use on 11 meters. I took it home and tested my antennas. Then I had another ham with a nice Bird and the right slugs to test behind me. Sure enough I had lowered the SWR on my wire antennas (HF Band) as low as they would go. That cheap little meter served me for about 4 years until I became gainfully employed and bought a Bird Watt Meter. It was a simple diode detector and was wildly sensitive up on 2 meters my highest band at the time but it worked. It's only scaling was relative even for the 11 meter band. Of course I never operated with it as it's diode detector probably poured out harmonics. Point being relative was good enough to do what I needed to do. I probably learned more about antenna during that period of time than any other in my life with only a cheap little CB band SWR meter and watching my plate current!

    Dude, keep up the good work. You should PM the guy here Winegard. He works for them and might possibly ask him to sample some antennas to you.
    The more I understand, the less I know.

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  17. #17
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    Quote Originally Posted by EscapeVelocity View Post
    I heard someone claim stacked Winegard 6000s were better than the AntennaCraft FM6. The 6000s have half the boomlength, about 1/4 wave at FM frequencies, of the FM-6 which is about 1/2 wave. These are properly distanced of course.
    We OT but you brought up something I like to play with. Do you remember where or why the shorter Winegards stacked better?

    The FM6 as we have discussed a lot is a very old but proven design. Is the author you read claiming the Winegard even half the length are that much better?

    From pure theory, since twice the boom length is normally 3 db as would be stacking but no combiner loss on doubling the boom, normally a longer yagi is better than 2 short ones stacked (unless there are other things you are trying for beside raw gain).

    I can repeat what I posted somewhere else today. My experience and those of a lot of guys I used to play with on 2 meter (144.1 MHz) SSB found that stacking vertically gave them more range than a long boom yagi when they were restricted to no more than roof top mounting (not on a 50 ft tower, etc). We always assumed it pointed more of the signal at the horizon, which my stacked YA-1713's appear to prove out as well pointed at Jacksonville. I do wish my YA-1713's though were about twice as long.
    Last edited by Piggie; 12-28-2009 at 11:34 AM.
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  18. #18

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    Quote Originally Posted by Piggie View Post
    I have a pair of YA-1713's stacked 40 inches vertically.
    ... and ...
    A story of my own.
    I did read with interest your description of the stacked Y10-7-13's. Its a respectable piece of empirical work and I appreciate the contribution. Gives me a little pause about my own plans for my modified unit. I've been pondering spatial diversity a lot lately. I never really needed the gain; I needed better directivity and that was the original motivation. However, (I've begun to theorize) multiple units may perhaps have a small advantage. The following is a comment I left at the highdefforum related to UHF receptioin.
    ---------------------------------------------------
    I've often pondered the notion that where reflections are a significant contributor to quality (or lack of), the 8-Bay designs in general might provide better long term performance. There is a little bit of a concept of spatial diversity involved. A Yagi design, like the 91XG, concentrates energy along a single axis. On the other hand, an N-Bay design aggregates signals received along N different axes. At UHF wavelengths the separations between active elements approaches several wavelengths. It is easily imaginable that if you could independently observe the waveform levels and quality (I, mean "flatness"; absence of serrations), of each contributing element, there is some non-zero probability that at one point in time one element might produce the most optimal signal, while at other times some completely different element would be the better contributor.
    ---------------------------------------------------
    I'd invite comment on that concept! (Note that it ignores level, focusing instead on flatness).

    By the way I also appreciated your anecdote about the VSWR meter of your youth! Its that necessity being the mother of invention thing. I've been there!

    Best Regards,
    t

  19. #19
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    Do you remember where or why the shorter Winegards stacked better?
    I think he was saying that he stacked 2 Winegard 6000's and they perform better than a single FM-6.

    Im not familiar enough with either antenna to speculate much. The Winegard's are 4 element with 2 driven elements in the center in a log yagi configuration that Winegard likes to use.

    The FM-6 I dont know much about except that it has 6 elements and is a 1/2 wave boomlength.

    The Winegard is about 33" which is right around a quarter wave at FM transmission frequencies.

    I think the Winegard 6000 is a gem, and have marked it on my FM Antenna Guide that I have been neglecting of late, as a Best Buy.

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