Vertical dual band, what's best?

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by W0PWN, Jun 2, 2021.

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  1. W0PWN

    W0PWN Ham Member QRZ Page

    I realize that's somewhat of a tricky question. I lack the space for what some might call a proper vhf/uhf antenna. And I'm new to the ham world so I'm wondering if verticals like those from Diamond and Comet are better performing than say a J-pole (copper or twinlead cable)?
    Also.. am I right or wrong in thinking the biggest difference is gain?

  2. N8TGQ

    N8TGQ Ham Member QRZ Page

    No matter how much gain you have, VHF & UHF will only go a little beyond the horizon. Heighth is the easiest way to go farther.
  3. VA3QY

    VA3QY Ham Member QRZ Page

    Personally, i prefer Slim-Jim. Field use and use in airfields where we are using it show a clear advantage. People may disagree. But between j-pole and slimjim; i would opt for 2nd.
  4. W0PWN

    W0PWN Ham Member QRZ Page

    And (correct me if Im wrong) but by slim-jim you mean the j-pole style that has the longer portion wrapping back down towards the shorter arm, right? Also if you are looking at a base station, would you use pipe or wire?
    VA3QY likes this.
  5. W0PWN

    W0PWN Ham Member QRZ Page

    Thanks for this... I am planning on going a bit higher.
  6. AK5B

    AK5B Ham Member QRZ Page

    Apples and rotten oranges. Diamond and Comet and many others manufacture collinear VHF/UHF antennas with real gain (they are stacked 5/8th wave lengths that compress the pattern in the vertical plane), whereas j-poles are fraught with common-mode currents on the coax (part of how they radiate, essentially).

    I suggest starting out with an ordinary 1/4 wave ground plane that you can make yourself with 5 pieces of wire and a SO-239 panel mount connector. Get that together and up in the air fed with good low-loss coax (LMR-400, RG-8/U, DXEMax400, etc) and see how well it performs---you might not need all the gain the commercial offerings can provide anyway.


    W0PWN likes this.
  7. KI8DJ

    KI8DJ Ham Member QRZ Page

    Tram 1480 is a good performing antenna 2 5/8 waves on 2m and 4 on 70 cm. Nearly the same construction as the Diamond and Comet but considerably cheaper. About 8 feet long has 19 inch radials.
    AK5B likes this.
  8. WB8NQW

    WB8NQW Ham Member QRZ Page

    I have a Diamond 510 antenna at 60' fed with 100' of 1.25" heliax. The antenna has about 8db gain at VHF and 11db gain at UHF. The feed line loss is .6db at 450MHZ. It opened up a whole new world for VHF/UHF communications.
    KB2SMS and AK5B like this.
  9. W4EAE

    W4EAE XML Subscriber QRZ Page

    With VHF/UHF verticals, gain can be important; but not as important as the lower radiation angle that gain gives you.

    Two stacked 5/8 waves will give you a significantly lower radiation angle than a 1/4 ground plane will. This can matter a lot if you are on relatively flat terrain, can mount it high enough, and wish to reach stations/repeaters more than 30 or 40 miles away. I have had both types on antenna at the top of my 50ft mast, and the performance difference is substantial.

    If the antenna is relatively low (less than 20ft), then you are likely not to reaching that far no matter the antenna. At my house, the stacked 5/8ths now reside at the top of the 50ft mast; and the 1/4 wave ground plane is on the roof of my single floor home.

    As far as performance goes, I have no reason to think that the Tram antennas are lesser than the Comet or Diamond antennas. Just from the appearance of quality straight out of the package, I would say that Comet is the best, with Diamond a little bit ahead of Tram.
    AK5B likes this.
  10. K1LH

    K1LH XML Subscriber QRZ Page

    A J-pole including the 1/4 matching stub is near 5ft long.

    A Comet GP-1 is 4'2"
    A Comet GP-3 or Diamond X50 (they pretty much the same thing) is 5'11" and 5.6ft respectively per their websites

    I'd recommend getting a GP-3 or X50, I've had an X50 for years, it just works and works well.

    At the same time, nothing wrong with building your own J-pole, they do benefit from a second decoupling stub - , but that adds more length making them over 6ft long in total.
    Last edited: Jun 2, 2021
    AK5B likes this.

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