Inverted L vs Double Bazooka 40 Meters WSPR 24-hours

Discussion in 'Amateur Radio News' started by W3GTR, Nov 18, 2020.

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  1. W3GTR

    W3GTR Platinum Subscriber Platinum Subscriber QRZ Page

    Over the past two days I have been running 24-hour periods of WSPR on both my Inverted L and Double Bazooka antennas on 40 meters. I realize there may be differences in propagation between two days, so it’s not a perfect comparison but it’s the best I can offer. Both antennas performed extremely well transmitting 200 milliwatts of power. WSPR Report.jpg
     
  2. W6NEL

    W6NEL Premium Subscriber QRZ Page

    Great timing, I was waffling on buying the 40m Double Bazooka
     
    W3GTR likes this.
  3. W3GTR

    W3GTR Platinum Subscriber Platinum Subscriber QRZ Page

    Worked well on 40 of course. :)
     
  4. K3XR

    K3XR Ham Member QRZ Page

    Been using WSPR the past few days on 30 meters into a vertical quad loop with good results. Antarctica, Japan, Australia, and So. Africa and of course lots of US and European stations. Have not used it to compare different antennas but that should make for some interesting results.
     
  5. KM1H

    KM1H Ham Member QRZ Page

    Save the waffles for your stomach.
    The DB works with some loss over a dipole that most wont be able to notice. It also costs more for no extra benefit. It also deteriorates over time.

    Trying to compare a DB to an Inverted L is like comparing apples to pears. Different polarizations are involved. Try comparing to a simple dipole at the same height and orientation and at the same time. Anything else is a waste of forum space.
     
    K2XT likes this.
  6. N1FM

    N1FM Premium Subscriber QRZ Page

    Interesting, I don't know what the difference was, propagation-wise, between the two periods, but I wonder if the lower noise level on the Bazooka allowed you to work more Africans, ZL stations, and the FR5ZX station?
     
  7. K2XT

    K2XT Premium Subscriber QRZ Page

    There is no lower noise level. That is one of the myths about this antenna. It is merely a dipole made out of coax, with a useless quarter wave shorted stub on each side that does absolutely nothing to enhance performance. In this case the exact same results would have been obtained with a simple horizontal dipole.
    For some reason hams have this crazy idea that if the feedpoint has a dc short across it it lowers the noise. Not so, but if it was true the benefit could be obtained with an rf choke or simply a resistor.
     
  8. N1FM

    N1FM Premium Subscriber QRZ Page

    I was referring to the noise difference between an Inverted L and a Dipole -- not the difference between a 'double bazooka' and a simple horizontal dipole. I'm not sure there is a difference between a dipole and a double bazooka, although some users swear the bazooka is quieter, but that's not at issue in my question.

    Many hams live in close proximity to low angle noise from their neighbor's noisy apparatus, of all kinds, and local noise from power lines.

    An inverted L is an end fed vertical antenna, which is more susceptible to close-proximity, vertically oriented noise sources, because the angle of incidence is lower than a dipole in both transmission and reception.

    Higher angle antennas, like dipoles / double bazookas, hear man-made noise at the first hop, and from unique directions on the azimuth. We can prove this by rotating a dipole, to null noise. This noise comes from father away, at higher angles of incidence, but the inverse square law reduces this noise considerably as opposed to noise heard by a vertical. The inverse square law states that the magnitude of one's exposure drops dramatically, proportionally to the square of one's distance from the source. Conversely, the magnitude of one's exposure also increases dramatically with proximity. This is true of SAR and radio reception in general.

    That's why people using an inverted L often use a receive antenna, like a Flag, K9AY loop, and a coaxial choke near the radio location, and an UNUN, at the base of the vertical / Inverted L. These reception-helpers reduce the local noise reception characteristics of verticals and inverted L antennas. If you live in the sticks, noise is not as much of a problem, as the locally generated noise is less because there are fewer neighbors and noise sources, but in the city and suburbs, local noise is a bear, and much worse than a dipole or double bazooka, when using an inverted L or standard vertical antenna.

    Here are some tools low band ops use to reduce local noise reception on vertical antennas:

    https://palomar-engineers.com/tech-support/tech-topics/vertical-antennas
     

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