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Thread: rhombic antenna for 80 meter band

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  1. #1
    Join Date
    Jan 2000
    Location
    orlando fl USA
    Posts
    55

    Talking rhombic antenna for 80 meter band

    hi
    i am looking for a rhombic antenna desingn, i got over 2 acres of land to get this one working, if any got info on this one i appreciate, thanks.
    Last edited by WP4IFO; 01-19-2010 at 03:47 AM.

  2. #2

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    A rhombic is normally at least a few wavelengths long, and to achieve maximum gain is terminated and directional.

    A few wavelengths at 80m is about 800 feet on 80m. 2 acres is about 88000 square feet, or if it were "square," about 300 feet on a side.

    That normally would not be enough real estate for an 80m rhombic, but try it and let us know what happens!

  3. #3
    Join Date
    May 2006
    Location
    SeaTac, WA
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    502

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    For a standard 3 wavelength design:

    831 feet each side
    1512 feet long
    736 feet wide.

    For bidirectional just feed it with 600 ohm open wire line... for unidirectional you would need to build a 600 ohm termninating resistor and put it at one end.

    Make sure you get it up at least 140 feet.

    Should get you 10dbd gain on lower end of 80.

    Let me know when it's done and I will give a listen for it.

  4. #4
    Join Date
    Apr 2002
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    the beautiful tree lined banks of the ruisseau de merde
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    2 acres might get you a ten meter rhombic if they were right next to each other, 208'x416'.

    an 80 meter rhombic would require better than 20 acres!

    a "20" is 660 feet wide by 1320 feet long!
    ALBA GU BRA

    SAMUEL FINLEY BREESE MORSE
    BORN APRIL 27, 1791,DIED APRIL 2, 1872
    INVENTOR OF THE ''MORSE''CODE, THE WORLD'S FIRST TRULY LONG RANGE COMMUNICATIONS SYSTEM

    eat more moose. 10,000 wolves can't be wrong !

    THE SECOND AMENDMENT OF THE U.S CONSTITUTION
    IS AMERICAS ORIGINAL HOMELAND SECURITY SYSTEM !

  5. #5
    Join Date
    Apr 2002
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    the beautiful tree lined banks of the ruisseau de merde
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    2 acres might get you a ten meter rhombic if they were right next to each other, 208'x416'.

    an 80 meter rhombic would require better than 20 acres!

    a "20" is 660 feet wide by 1320 feet long!
    ALBA GU BRA

    SAMUEL FINLEY BREESE MORSE
    BORN APRIL 27, 1791,DIED APRIL 2, 1872
    INVENTOR OF THE ''MORSE''CODE, THE WORLD'S FIRST TRULY LONG RANGE COMMUNICATIONS SYSTEM

    eat more moose. 10,000 wolves can't be wrong !

    THE SECOND AMENDMENT OF THE U.S CONSTITUTION
    IS AMERICAS ORIGINAL HOMELAND SECURITY SYSTEM !

  6. #6
    Join Date
    Apr 2002
    Location
    the beautiful tree lined banks of the ruisseau de merde
    Posts
    5,285

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    oops! my foot slipped again!
    ALBA GU BRA

    SAMUEL FINLEY BREESE MORSE
    BORN APRIL 27, 1791,DIED APRIL 2, 1872
    INVENTOR OF THE ''MORSE''CODE, THE WORLD'S FIRST TRULY LONG RANGE COMMUNICATIONS SYSTEM

    eat more moose. 10,000 wolves can't be wrong !

    THE SECOND AMENDMENT OF THE U.S CONSTITUTION
    IS AMERICAS ORIGINAL HOMELAND SECURITY SYSTEM !

  7. #7
    Join Date
    May 2002
    Location
    Kaluga, Russia
    Posts
    16

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    Reminds me of a story about two amateurs.
    One sais:
    - Hey man I bought a peace of land next to my property to set a 500 meter beverage.
    - Oh! That must have cost you a fortune!
    - Not at all! It is 500 meters long and 10 centimeters wide!

    Well to the question:
    Have a look at the diagram. L is only one leg of four. So the length of the antenna is going to be a bit shorter then double L. And as you can see the diagram shows figures for 10 Mhz.
    So if I were you Id start thinking about either vertical or switchable 2 el Delta loop like this:
    http://dl2kq.de/mmana/4-3-37.htm - very last one remeasured to 80 meters.
    Attached Images Attached Images
    Serge, RX3XX,
    Kaluga, Russia.

  8. #8

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    The late ZL2BE had 3-wire rhombic antennas (3 wires on each leg instead of the more common single wire) that were 20 wavelengths on a side at the lowest frequency. Since rhombic antennas operate on "powers of 2" in terms of frequency he had to have separate rhombics for 15 meters. His "main" rhombics were for 160, 80, 40, 20, and 10 meters (1, 2, 4, 8, and 16 times the frequency). Since the 15 meter band is 12 times the 160 meter frequency an antenna "cut" for 160 meters would not work.

    These rhombics were installed on wooden poles that were 90 feet above ground. Needless to say, he had an excellent signal. Back in the "AM Days" the 15 meter band would appear to be completely "dead". However, as you tuned across the band your "S" meter would suddenly be "pinned" and there was ZL2BE. No other stations could be copied but he was definitely "armchair copy".

    Now he was one of the largest, if not "the" largest, sheep ranchers in New Zealand and could definitely afford the very extensive antenna system that he had.

    Glen, K9STH

  9. #9
    Join Date
    May 2007
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    Etna PA
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    Quote Originally Posted by K9STH View Post
    The late ZL2BE had 3-wire rhombic antennas (3 wires on each leg instead of the more common single wire)
    Every rhombic antenna I ever worked on professionally was a 3 wire design. The 1 wire design is a amateur "get by", for when you don't have the $$ to do it right.

    that were 20 wavelengths on a side at the lowest frequency. Since rhombic antennas operate on "powers of 2" in terms of frequency he had to have separate rhombics for 15 meters. His "main" rhombics were for 160, 80, 40, 20, and 10 meters (1, 2, 4, 8, and 16 times the frequency). Since the 15 meter band is 12 times the 160 meter frequency an antenna "cut" for 160 meters would not work.
    Powers of 2? HUH? often the pros will "nest" 2 rhombics inside one another, you can get 2 antennas on the same patch of ground, obviously, the larger one will have a greater gain especially at lower frequency's. It's simply a way to get 2 antennas for the (land) price of 1.

    These rhombics were installed on wooden poles that were 90 feet above ground. Needless to say, he had an excellent signal. Back in the "AM Days" the 15 meter band would appear to be completely "dead". However, as you tuned across the band your "S" meter would suddenly be "pinned" and there was ZL2BE. No other stations could be copied but he was definitely "armchair copy".
    That's not how it works at all.

    Double the size of a rhombic and you get 3 DB more gain.

    A VERY LARGE rhombic antenna might give you 20DBd of gain in the upper HF bands, about 3-4 s-units over a dipole. figuring about 60-80 db range between "dead" and "pinned", You would need a rhombic about the size of New Zealand to do this mythical signal.

    Now he was one of the largest, if not "the" largest, sheep ranchers in New Zealand and could definitely afford the very extensive antenna system that he had.

    Glen, K9STH
    Rhombics CAN produce significant gain. They take HUGH amounts of real estate to do it, dozens, or even the better part of hundreds of acres depending on the frequency.

    They also cover a enormous frequency range, and are VERY useful to "ride the MUF" (Maximum usable frequency) for point-to-point service.

    I maintained 8 dual nested rhombic antenna arrays on Diego Garcia. (4 rx,4 tx)They were pointed at Alice Springs Australia, and Asmara Ethiopia. They had a peak gain of just about 20DBd in the upper HF band.

    The antennas were over 1000 feet long. And about 100' up

    Because of the nulls in the radiated beam, they were POOR antennas for communicating with the fleet underway, as a few hundred nautical miles difference in the ships position on the 1st hop would easily put you from the +20DBd lobe into the -20 DBd null BETWEEN the lobes.

    They were about 2 s-units louder, on average, than a 3 el 20M Yagi @ 50 ft. Hardly a signal that would pin the s-meter when nothing else was getting thru.

    Rege
    Now my mistakes travel at the speed of light!:cool:

  10. #10

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    3V:

    Actually, when I was hearing/working ZL2BE I didn't even have an "S" meter! Like a good number of amateur radio operators during the late 1950s and into the 1960s we used our "ears" to determine signal strength. Frankly, my Hallicrafters S-85 didn't have an "S" meter although its slightly bigger brother, the SX-99, did have one.

    However, the signal from ZL2BE often was the only signal heard on the 15 meter band, especially during the evening hours CST, and he was always strong. I understand that he had a very strong signal on 20 meters as well. But, since my antenna, at the time, was a "true" Zepp cut for 160 meters and I didn't have a yagi on 20 meters, I generally didn't work much phone on the band. However, my 15 meter 2-element yagi did a pretty good job. By the way, my transmitter was a Heath DX-100.

    Glen, K9STH

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