“Best” Multi-band HF Antenna ?

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by K2POP, Jul 26, 2011.

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  1. K2POP

    K2POP Ham Member QRZ Page

    "Best" is what ever YOU think is best. I am not looking for recommendations - because you don't know enough about the circumstances. I'm just asking what HF antennas the readers like best - from their own experience, experience of friends, or from their readings and study.

    Thanks for your interest,
    Richard
     
  2. M0GVZ

    M0GVZ Ham Member QRZ Page

    Err, no. A dipole THAT YOU CAN GET UP HIGH ENOUGH will outperform a vertical. However I can't see many people getting up a 40m or 80m dipole and struggling to get a 20m dipole up high enough to beat a properly installed 1/4 wave groundplane vertical in the UK once you get to around the 3000 mile range and even then, it'll only beat the vertical in a total of 60 degrees out of 360 so unless you have a way of rotating this 33,66 or 132ft dipole, the vertical will beat it hands down for 300 out of 360 degrees and for approaching 90 degrees of that by up to a hundredfold.
     
  3. EI4GMB

    EI4GMB Ham Member QRZ Page

    I think what you're basically trying to say is that a vertical is omni-directional and a dipole is bi-directional. Agreed. But it has been proven by EZNEC modelling that a vertical shows no marked improvement in low angle radiation over a dipole installed a half-wavelength above the ground. Furthermore it has been shown that a bi-directional dipole performs better both on DX and NVIS in its favored directions. A dipole also displays substantially more bi-directional gain than a 1/4 wave vertical which displays no gain at all.
    If you want to argue with the findings of EZNEC modelling that's your business. Personally, I never do.

    Best Regards

    Fred EI4GMB
     
    Last edited: Jul 28, 2011
  4. N0AZZ

    N0AZZ Ham Member QRZ Page

    The only thing I can go by is what I have a dipole at 55' and a HyGain HY Tower with a very good radial system I have them on a coax 1/2 switch on my Palstar tuner. I have beam antennas for 2-40m so only use them for low bands and the vertical 90% of the time will out perform the dipole hands down on all Dx contacts on 80m. NVIS is a different all together just the opposite. For a antenna that is used for NA contacts the vertical will let you hear both sides of the QSO.

    I use it alone for QRP with my IC-703+ for all bands running JT65HF and SSB hard to beat.
     
  5. KJ3N

    KJ3N Ham Member QRZ Page

    How many people do you know that can get an 80m dipole 132 feet in the air? How many can get a 160m dipole 265 feet in the air?

    There's what EZNEC shows and then there's reality. In reality, a vertical will trump the typical 160m or 80m dipole (usually not higher than 50 feet) for DX because it will have a lower TOA. Sure, the dipole has gain, but typically at uselessly high TOAs.
     
  6. EI4GMB

    EI4GMB Ham Member QRZ Page

    Guys, there are more bands on HF than 160m/80m! Think of 40m,30m,20m,17m,15m,12m & 10m. Get real!:p

    73,

    Fred EI4GMB
     
  7. M0GVZ

    M0GVZ Ham Member QRZ Page

    If you are wanting an antenna that gives the best performance in an omnidirectional pattern, a dipole is NOT it.

    Lets take a 20m dipole 1/2 wavelength above the ground and modelled using EZNEC.

    At a 15 degree take off angle the dipole running north-south only beats a vertical in east and west directions and then only by 40 degrees either side of east and 40 degrees either side of west. Using a reasonable DX takeoff angle of 15 degrees, the dipole only has 4dBi more gain than a 1/4 wave vertical and to the north and to the south, the vertical antenna is 8dBi better than the dipole and for over 180 degrees of a full circle, the vertical beats a dipole. And thats modelling using EZNEC. As the take off angle is lowered to 10 degrees, the performance gap narrows east/west and the gain of the vertical over the dipole increases north/south
     
  8. KA4DPO

    KA4DPO Platinum Subscriber Platinum Subscriber QRZ Page

    I have read this thread from start to finish and I am amazed that no one has suggested an inverted V. You stated in your original post that you have a wide range tuner. A 30 foot mast will support a 40 meter inverted V and will even support an 80 meter drooping dipole if you have the room to fan the ends. Such an antenna will probably not be a barn burner because of ground proximity.

    The simplest way to go about it is to put up an Inverted V fed with 450 ohm ladder line right to your tuner. Make the antenna elements as long as you have room for as long as they are the same length and terminate them at least a foot above ground. The tuner will do the rest but you may have to play around with the feedline and antenna element lengths to get it to tune up on all bands.

    An inverted V will work about the same as a vertical antenna but without the need for ground radials. Since there are no free lunches the compromise comes about on the bands above 20 meters where the antenna will have many high gain lobes and deep nulls in every direction. This is not necessarily a bad thing since if a station falls under one of the lobes the atenna will have gain over a half wave dipole. If a station is not within one of the lobes you might not hear them or, they will be attenuated.

    So that's my two cents worth for the simplest to build, most inexpensive, and yet probably the easiest to get going multi-band (I don't like all band) antenna. Best of luck with the project and have fun experimenting.
     
  9. KJ3N

    KJ3N Ham Member QRZ Page

    Maybe next time you'll properly qualify your statements. But, I won't hold my breath. :rolleyes:
     
  10. KA4DPO

    KA4DPO Platinum Subscriber Platinum Subscriber QRZ Page

    Looks like you started quite a fire here Richard. There are no magic antennas but there are trick antennas. All multiband antennas have tradeoffs. A roof mounted vertical with tuned radials will work great but looks really ugly.. A single end fed wire can be very stealthy but requires a very good RF ground system and can present RF feedback problems under some conditions. A fan, or whisker dipole combines resonant dipoles for each band and can be fed by coax but even one with 40 meters as the lowest band is heavy and needs to be up at least 30 feet to work halfway decent.

    Once again a lot depends on the bands you want to work. If you want to operate on 160 you will need enough realestate to put up either a dipole, a sloper, or an inverted L. The inverted L takes the least amount of space but like all end fed antennas requires an exceptionally good RF ground in order to be effective. Also, 160 meter antennas do not usually make good "all band" antennas for several reasons.

    Stay away from no radial verticals unless you just want to heat up the coax, they are not very efficient radiators. Also, very short loaded antennas are also not very efficient and are normally very narrow banded, that is they will only operate on a very narrow segment of each band. Trap verticals fall into this category, they work well but are very narrow banded on the lower bands like 20 meters through 80.

    The two easiest all band (multi-band) antennas are a dipole (straight or inverted V) fed with balanced line connected to an appropriate tuner. Or, a random length (not quite true) end fed wire with a good RF ground system connected directly to the wire port on a good tuner. Because you have a tuner, these antennas will tune the entire band for any band they will reasonably load up. I left out the fan dipole, not because it isn't a good antenna but because it is more difficult to build and get working. A dipole that is center fed with ladder line (that includes the Inverted V) is the easiest to get working and will work as well as any multi-band antenna that I have ever used, and that is a lot of antennas.
     
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