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Directional 11 meter for SSB to europe

Discussion in 'CB Antennas' started by mb91w126, Jul 29, 2014.

  1. GnG8d

    GnG8d Well-Known Member

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    That's going to be a little different than a small homebrew on a pushup pole. You'll need to concrete in a base and erect a tower for anything that big.

    Over earth (ground gain) the dipole will show ~7dBi, and the moxon ~10dBi. To get into 15-20dBi territory you are talking at least a 5 element yagi.

     

  2. GnG8d

    GnG8d Well-Known Member

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    The lobes are broadside to the long axis of the dipole no matter the configuration. The pattern shape changes slightly in that the deep nulls are lessened on either of the V configurations, but the radiated lobe direction remains the same. In other words, if you took an inverted V and simply let it fall over horizontal, the directionality wouldn't change.
     
  3. mb91w126

    mb91w126 Active Member

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    Thanks for all the info. What I like about this forum is that not only do you get direct answers but on topic side conversations that are educational.

    I'm still up in the air about which direction to go.
     
  4. Mudfoot

    Mudfoot Elmer

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    Thought you wanted to beam Europe.
     
  5. GnG8d

    GnG8d Well-Known Member

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    The most important thing to do is get something, anything in the air before this solar cycle peters out!
     
  6. jazzsinger

    jazzsinger Bullshit Buster

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    Try any 3 element beam with 5/8 wave a few feet above, best all round compromise and most cheap rotators will handle it, i ran a 3 ele and mighty magnum 3 on a 10ft pole to rotator strapped to chimney and 6 ft pole above rotator with beam halfway and magnum above at top, almost no noticeable interaction and could pick off usa at will on either antenna.

    3 element beam lacks gain of bigger antenna, but has bigger beamwidth giving you more chance of hitting your desired target even when not on exact bearing, i did general listening on vertical, once i knew where long range paths were set beam on that heading and battered in with ease, a pdl 2 is another fantastic choice if you can source one.

    Sirio do the sy-3 at reasonable price but you can get better build quality and optomised versions, but in all honesty for the extra gain or strength probably isn't worth the extra outlay,

    you can also mount it on a 20ft 50mm aluminium or steel pole to rotator and 6 foot pole above it, the 6 ft pole i'd go for 10 gauge for 2 antennas, when wind gets so strong its going to snap antennas, not much will stop it, cheaper to replace cheap antennas than dear ones. I might just use a standard 16 gauge 6 ft mast 1.5-2" diameter, as much better/cheaper to replace a broken mast than broken antenna.

    hopefully if i can get permission, i plan to do exactly this, with a Hy Gain 533 CB3 beam and CLR2, but if I didn't have them I'd use a Sirio sy-3 and Sirio 827 or tornado 27 (i have that too),

    I wouldn't expect to see much if any performance difference from either setup, just Hy gains are slightly stronger, but in winds that break antennas that ain't gonna cut a lot of ice.

    And we have no shortage of winds like that, so may even consider a telescoping 10 gauge mast made from 5m sections with 1m overlap to rotator and a 6ft 16 gauge mast that hopefully breaks before antennas on it.

    chimney mounting is another option as is T and K brackets with top one mounted just below gutter. I've never found a tower essential for small 11m beams or verticals, as long as you use strong masts with a slightly weaker top section, things should be good, a strong top section with no give puts all windload on antenna/s,

    I've seen the outcome too many times, smashed up yagi's and verticals that usually snap within a foot or two from mounting bracket, much cheaper and easier to source a new mast part than antenna part/s.

    That way I can drop it in bad weather and use building to shield it as building would be between antenna and prevalent westerly winds we get off Atlantic. :)

    I'm near Glasgow in Scotland and consider the East coast of N.America a rig check, either homebase or mobile, you shouldn't find it hard in the right conditions,

    if wanting to know if UK propagation is runing, monitor 27.555 usb or 27.78125 Ch19 ukfm, some high power stations on those frequencies will be first to show, just as we monitor superbowl for early signs of US skip.
     
  7. jazzsinger

    jazzsinger Bullshit Buster

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    2 points,

    Firstly achieving 3db gain is not as easy as it sounds, needs good ground and correct spacing conditions.

    Secondly you can't just use two equal lengths of 75 ohm coax, they must be exactly a 1/4 wave allowing for velocity factor or odd multiples of a 1/4 wave, ie 1/4, 3/4, 1 1/4, 1 3/4 or it won't work properly.

    the technical name is an impedance inverter, it will step antenna impedance up to 100 ohms and when you do it to both you can parallel 2 x 100 ohms to get 50 ohms.

    on rg58 rg213/u a 1/4 wave is approx 6ft, due to .66 velocity factor so 6ft, 18ft, 30ft, lengths of 75 ohm .66 vel factor coax would all do same job, rg59 would do it, but rg11 would do it with less losses. you can use any velocity factor coax, you just multiply the free space 1/4 wave for your centre frequency times the velocity factor for a 1/4 wave multiple length.

    Free space 1/4 wave can be found by dividing 300/27.xxx/4, answer will be in metres, to convert to feet multiply by 3.28, to convert feet to inches multiply by 12.

    once you have your 1/4 wavelength you can multiply it by any velocity factor, as long as you do this and stick to 75 ohm coax you should do ok, although i'd be very surprised if you get full 3db gain.

    to swr it, attach a 50 ohm dummy load at one antenna side whilst you adjust the other and vice versa, lie the other antenna flat on ground as you tune alternate side for lowest swr, once you've tuned both for lowest swr put both antennas on vehicle or masts and you should still have a low swr on both.

    Personally i think its a waste of effort, money and not worth the hassle when a 3 ele is 360 degree capable and not much dearer with more gain on a vehicle its pointless too as you very rarely have the necessary distance to achieve the gain, an omni pattern from a centrally mounted antenna is a better bet :)
     
  8. The DB

    The DB Sr. Member

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    3 dB gain in two directions over what? It won't be 3 dB in gain over a single 1/4 wave whip, so what will it be 3 dB in gain over?

    The RG-59, or any 75 ohm feedline, needs to be an odd multiple of 1/4 electrical wavelength or you will have all kinds of problems tuning it, if tuning it will even be possible. Further, they need to be the same length.

    Near 1/4 wavelength between the antennas as described will net you about 1.1 dB over a single antenna of that type in two directions. If you want 3 dB in gain in those two directions you need to be close to about twice that separation. Further increasing the separation to 5/8 wavelengths will maximize the gain.

    This same separations can work with other antennas, say you had two Penetrators, the same gain over a single antenna of the type used would still be present in two directions.

    If it were me, I would build a small beam. A well designed two or three element yagi or quad will take up far less space and get good gain in one direction, with good rejection in all others.


    The DB
     
  9. mb91w126

    mb91w126 Active Member

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    As a short term compromise I chose a maco y-quad. While poking around antenna design tools, I discovered http://www.ve3sqb.com had a q yagi and s quad designer.

    I enter 27.375 into both and the spacing between driver and reflector are remarkably longer than the 68" in the y-quad instructions.

    are the modeling programs trying to tell me something or should they be discounted and I should just blindly follow the manufactures' crappy assembly instructions?

    your thoughts
     
  10. mb91w126

    mb91w126 Active Member

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    the yquad is up. I pointed it toward Boston and made contact w/ LA area. go figure.
     
  11. Mudfoot

    Mudfoot Elmer

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    You like it?
     
  12. Dipole

    Dipole Active Member

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    Horizontal wire center fed dipole with a 4:1 balun 20-30 ft up runing N>S will radiate E>W. Works for me just fine.
     
  13. vkrules

    vkrules Sr. Member

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    Just when you think you have the direction sorted ,you encounter "longpath" and "backscatter" hope the beam is working for you.
     
  14. mb91w126

    mb91w126 Active Member

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    yeah , no kidding.. so now I have to go learn about those two "characteristics".
    so I rotated it to ssw. no easy feat as it's encumbered by tree limbs. Now I'm listing to lot on AL and GA. So when I call cq I receive responses from 90* from SSW.

    When it was directed to NE, I could hear one sided conversations from Florida to NH. I could hear Florida but not NH.?? Not to mention contacting CA.

    In my very limited experience, it seems to receive like a directional and transmit like a dipole. But, it's just 2 hrs on a single day, so we'll let it settle for a while.

    most enlightening was swapping the mk3 with a dx-949. the 949 was worthless compared to the mk3.

    learning as we go.....
     
  15. nosepc

    nosepc On Vacation

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    MY EXISTING ANTENNA 11 meters. It is a picture just "cubes quad" fed into the vertical side for a lower irradiation angle. After installed as square, I reformed by changing the form to get an even lower angle, making trapezoidal. This is optimal, and have made many DX to Europe, Central America, USA; with only 12 watts. I live in Argentina, Gualeguaychu.[​IMG] [​IMG]
     

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