Curious

Discussion in 'VHF/UHF - 50Mhz and Beyond' started by W9EAM, Aug 26, 2021.

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  1. W9EAM

    W9EAM Ham Member QRZ Page

    Can you co-phase to dishes?
     
  2. K3EO

    K3EO Ham Member QRZ Page

    Certainly! Radio astronomers make use of radio interferometers usually on very large scales. Several smaller dishes are combined together to give the same performance as one large dish. For example the Very Large Array in New Mexico takes advantage of this technique. See link: https://www.britannica.com/topic/Very-Large-Array

    From an amateur astronomer or ham radio standpoint, you can co-phase a couple of Direct-TV dishes together. The beam width will be narrower and the pointing of the dishes will be more critical, but the gain and resolution will be improved.
     
    K0UO likes this.
  3. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    "Co phase" is a weird expression, but putting antennas in phase and aimed in the same direction works.

    And it's "two."

    But anyway, of course you can. The trick with dish antennas is to be effective (have substantial gain) they are extremely directional with very narrow beamwidth, so finding the correct way to phase them for added gain takes complex mathematics and a really good understanding of each dish's aperture, which is directly related to its gain.
     
    Last edited: Aug 27, 2021
  4. WA2CWA

    WA2CWA Ham Member QRZ Page

    "Co-Phased Antennas" was the catch phrase back in the 70's. Truckers loved their co-phased "Big Mommas" on the mirrors of their trucks. Co-Phase antennas even had a draw for home use

    [​IMG]
     
  5. WG7X

    WG7X Platinum Subscriber Platinum Subscriber QRZ Page

    Gosh, I just love this tech-talk! Can we discuss SWAR's next? Huh? Can we?
     
    KA0HCP likes this.
  6. KM1H

    KM1H Ham Member QRZ Page

    A pair of similar dishes still has the ~ 3dB gain of a pair of dipoles.

    Carl
     
  7. W2EV

    W2EV Ham Member QRZ Page

    I wonder what drives you to ask this question? Understanding your goal may allow us to provide you with guidance that you may not have considered.

    For example, combining two dish antennas will provide 3dB of gain in a perfect world, however in practical terms...at microwave frequencies you are likely to lose at least 1 dB (and probably more) in the harness that you would use.

    On the other hand, you will get a true 3dB simply by using a dish that is 50% larger. You get 6dB by using a dish that is 2x in size. Both will be significantly less complex than "phasing" two independent dish antennas.
     
    KA0HCP likes this.
  8. W6KCS

    W6KCS Ham Member QRZ Page

    I can't think of any reason to do this except maybe EME. I used to work in point to point long haul microwave and have never heard of it being done. Usually any microwave path has enough "fade margin" that 3 dB either way isn't much of a factor. What's the application? In theory I don't see any reason it wouldn't work if the waves at the receiving end are in phase. I guess I can think of a few applications, like hooking up two similar 2.4 or 5.8 antennas for a slightly better path, but I think the benefit would be marginal. I agree with W2EV.
     
    W2EV likes this.
  9. W7HV

    W7HV Ham Member QRZ Page

    Phased array.
     
  10. K8JD

    K8JD Ham Member QRZ Page

    I stacked and split 6M Squaloes using the RG9 coax to rematch the Z of two ants to one coax feedline. .Got 3dB Omnidirectional gain :D
     
    K3RW likes this.

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