40 80 Double Bazooka

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by G0CSK, May 17, 2019.

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  1. G0CSK

    G0CSK Ham Member QRZ Page

    Can anyone give me any info how to make one of these Antennas, I have made monoband Bazookers but I think the 40 80 has traps”IE” 40mtr coax wound ones, but I can’t get any info on the measurements to the traps and any measurements after the traps? I know all measurements for a monoband 40 and also a 80 monoband antenna. I have seen the cameral 40 80 Double Bazooka is 103 ft overall So if anyone can help with the measurements or drawings for a 40 80 duel bander, I will be very grateful de G0CSK Peter
     
    Last edited: May 17, 2019
  2. KA0HCP

    KA0HCP XML Subscriber QRZ Page

    The ARRL Handbook and Antenna Book have had directions for decades (1970's on).
     
  3. AA5CT

    AA5CT Ham Member QRZ Page

    How do you put 'trap' a bazooka antenna? I'm not aware of a dual-band bazooka, but, maybe someone has worked out those details.

    Better yet, just make up a trapped dipole, using the coax shield as the conductors.
     
  4. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    I've never seen a trapped Double Bazooka, either.
     
  5. G0CSK

    G0CSK Ham Member QRZ Page

    ULTIMAX company makes them they are American just have a look on their web site or put it in google
    ULTIMAX8040 DUAL BAND TRAP DOBLE BAZOOKA
    Peter
     
  6. G0CSK

    G0CSK Ham Member QRZ Page

    I have made lots of trapped dipoles in the past. But the Double Bazooka is for quieter on receive and is wider banded and everyone I have made the VSWR has been flat throughout the band, Peter
     
  7. WA7ARK

    WA7ARK Ham Member QRZ Page

    Both statements also apply to my Bird Dummy load.
     
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  8. VE3EKJ

    VE3EKJ Ham Member QRZ Page

    I have a hard time seeing how such a bazooka would work. The stubs would be a dead short at the feedpoint for the second harmonic, which means an 80 meter bazooka would show a dead short at the feedpoint for 40 meters.

    Sometimes this is useful. Back a hundred years ago when I was a young lad and cable tv was not even imagined I couldn't use 10 meters because of TVI on tv channel 2, which is where the second harmonic fell. So I put up a 10 meter bazooka, hoping the second harmonic feedpoint short would be enough. It worked great! I logged lots of 10 meter DX contacts with ZERO second harmonic TVI!

    Bill VE3EKJ
     
  9. K4SAV

    K4SAV Ham Member QRZ Page

    Here is a video demonstrating the SWR of an 80 / 40 double bazooka. Notice that the SWR is less than 1.5 to 1 from 3.5 to 3.7 MHz. Also the SWR on 40 is less than 1.1 to 1 from 7.0 to 7.2. His antenna is very low, 20 ft at the center and 11 ft on the ends, but low to the ground does not account for the low SWR. Neither does being a bazooka. There is obviously a large amount of loss in the antenna somewhere. A trap dipole, using traps of Q = 180 and at the same heights as his antenna, but no feedline, would have SWR excursions above 6 to 1 over the 80 meter frequency range he measured.


    A typical single band double bazooka in free space would have an SWR max of about 3 to 1 over a 200 kHz bandwidth on 80 meters, with a power loss of about 10%. The crossed double bazooka would have an SWR max of about 2 to 1 over the same bandwidth, at the expense of 30% loss in power.

    Even with the crossed double bazooka, to get down to a max SWR of 1.5, you need some extra loss on top of that 30%.

    Many people continue to think that low SWR is the only important performance parameter. Many people also continue to erroneously think that an antenna that has a lower S meter reading on noise is a quieter antenna. That's why antennas like this sell.

    Jerry, K4SAV
     
    Last edited: May 18, 2019
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  10. VE3EKJ

    VE3EKJ Ham Member QRZ Page

    Well, that is a good explanation of a too-good-to-be-true SWR on 40 for this antenna, Jerry!

    Somebody is selling snake oil here. Reminds me of how back in the 70's during the CB craze I saw commercial microphone units claiming to fine tune your modulation. They were just a metal box with input and output jacks and a potentiometer inside between them.

    Bill VE3EKJ
     
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