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Best VHF UHF receive antenna?

Discussion in 'VHF/UHF - 50Mhz and Beyond' started by KE7RUX, Oct 1, 2019.

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  1. W5LZ

    W5LZ Ham Member QRZ Page

    It's already been mentioned, but the higher the better. And for the gain part and keeping the omnidirectionality(sp), a 'stacked' vertical array would probably be your best bet. eg: GP-9, etc. Basically it's a "what's it worth to you" thingy.
     
  2. W4EAE

    W4EAE Subscriber QRZ Page

    "The higher the better" is the only thing to be said with absolute certainty in every situation.

    My QTH is at a little of 300ft asl, which is reasonably good relative to the surrounding terrain. I have two VFH/UHF omni antennas. One is a 24ft Diamond vertical with the base at 80ft. The second is a copper pipe slimJim jpole mounted 4ft below the Diamond. Both are fed with LMR-600 (the run to the SlimJim being a few feet shorter).

    Most of the time, the practical difference between these two antennas on receive is negligible. (For information, the transceiver is an IC-9700). On transmit, the Diamond has a slight edge on the fringes of my typical range. This could be accounted for in the fact that the Diamond is radiating at ~15ft higher than the SlimJim.

    More gain vs more height--more height wins every time.
     
  3. KE7RUX

    KE7RUX Ham Member QRZ Page

    Thank you for your input.
    Wouldn't a 1/4λ radiation pattern only improve the ability to receive signals vertically (like airplanes), where a 5/8λ or other high gain antenna have radiation patterns that are specific for horizontal receive, or a tighter pattern as you mentioned, would be better for general use? I'm assuming the unwanted signals different than SWR, having not personally experienced receiving unwanted signals. In my grid, there is only a moderate amount of VHF/UHF activity, and so too many signals has never been an issue.

    In your experience, is a 1/4λ receive antenna better at receiving horizontal signals (also my intended use)?
     
    Last edited: Oct 10, 2019
  4. KE7RUX

    KE7RUX Ham Member QRZ Page

    Thank you for your input.
    What is the band and model of your discone?
    What is your typical gain on those bands?
     
    Last edited: Oct 10, 2019
  5. KE7RUX

    KE7RUX Ham Member QRZ Page

    Thank you for your input.
    In regards to having two antennas by each other, what would you say what horizontal distance and what vertical distance is required in between two TX antennas on the same band (VHF/UHF) to prevent overcrowding (for lack of a better term) the signals?
     
  6. W4EAE

    W4EAE Subscriber QRZ Page

    Both horizontal and vertical distance between antennas to prevent desensing is dependent upon frequency. Mine are not positioned optimally in this regard.

    For near to complete isolation, you would need vertical separation of about 10 wavelengths. Horizontal distance would have to be more than 100 wavelengths for the same.

    Acceptable separation is completely different depending upon the application.
     
  7. KF5FEI

    KF5FEI Ham Member QRZ Page

    If you live in a hilly area with repeaters on hills and your location is down low, the 1/4 wave might work better. Also good for listening to satellites.

    If you have a reasonably straight (horizontal) path to the repeater, the gain antenna would give you more range.

    If you want horizontal polarization, go with the proper antenna.
     
  8. AA7QQ

    AA7QQ Ham Member QRZ Page

    A Discone is similar to a 1/4 wave vertical in gain. But, it had continuous frequency coverage from 85 to 810 MHz. Look them up & you will see how they work.
    I am not sure of the brand, as I bought it used at a ham swap decades ago. It was about 10 years old when I bought it.
    It is great for VHF/UHF ham bands, scanners, FM broadcast & anything between 85MHz & 810 MHz.

    Ed
     
  9. AI3V

    AI3V Ham Member QRZ Page

    Couple points, in no particular order.

    http://aprs.org/LEO-tracking.html


    For true "line of sight" paths, there is nothing to be gained by height.

    But everything to be gained by gain:

    [​IMG]

    Discone antennas:

    [​IMG]

    Have a very wide vswr and gain bandwidth, but pretty mediocre gain and vswr.

    Most terrestrial vhf and above contacts are not "line of sight" but various "scatter" modes, perhaps the most common and usefull is "troposcatter":

    https://duckduckgo.com/?q=troposcatter&t=fpas&ia=about

    Height and gain are key to this mode.

    Rege
     
  10. W4EAE

    W4EAE Subscriber QRZ Page

    ...except an increased distance which can be considered 'line or sight.'

    ...like a roasted mountainside?

    In all seriousness, scatter is where the real action is.

    Troposcatter is fully dependent on neither height nor gain. Sometimes when an opening is there, .5 watts on a rubber duck can sometimes make the trip just as well as 100 watts on a yagi. Increasing your height can certainly increase to number of opening available to you though.
     

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