1. You can now help support WorldwideDX when you shop on Amazon at no additional cost to you! Simply follow this Shop on Amazon link first and a portion of any purchase is sent to WorldwideDX to help with site costs.

half wave antennas not needing ground elements?

Discussion in 'CB Antennas' started by BOOTY MONSTER, Aug 24, 2010.

  1. BOOTY MONSTER

    BOOTY MONSTER
    Expand Collapse
    Guest

    there's been a few post here saying that a half wave base antenna doesn't need ground elements . i just want some clarification on that . does a half wave not benefit at all or just minimally from ground elements ? or is it just that a half wave will tune and work fairly to pretty well without ground elements ?


     

  2. sp5it

    sp5it
    Expand Collapse
    Master of puppets

    Joined:
    Jul 9, 2009
    Messages:
    796
    Likes Received:
    322
    1/2 wave antenna does not need ground plane.
    Mike
     
  3. BOOTY MONSTER

    BOOTY MONSTER
    Expand Collapse
    Guest

    thanks 5 . do you think that it doesn't benefit from ground elements , or just that it will still be pretty effective without them ?
     
  4. Beetle

    Beetle
    Expand Collapse
    Sr. Member

    Joined:
    Dec 7, 2005
    Messages:
    2,839
    Likes Received:
    676
    A half-wave dipole (horizontally installed) doesn't need any ground plane or counterpoise.

    As for other variations on the "half wave" theme, try it with and without. See what works better for loading, for signal reports, etc. Many antennas that technically don't NEED a ground plane or counterpoise do work better with it.
     
  5. BOOTY MONSTER

    BOOTY MONSTER
    Expand Collapse
    Guest

    thanks beetle . i was thinking in terms of a 1/2 wave vertical , like a Ringo . a dipole has a ground element . whats going on is the guy i rent from was ok with me putting up a cb antenna , but i guess hes only seen antrons and imax antennas . he wasn't impressed with my four full length ground elements on my big home brewed 5/8 . since a 5/8 wont work effectively without ground elements (except for the imax) im thinking of just shortening the vertical of the 5/8 down to 18 feet and taking off the ground elements if i can still get pretty good performance that way ..... and keep the landlord happy . i could use the mast as a ground element , but i typically isolate the antenna from the mast and earth ground . i always use a coax coke .
     
  6. Shockwave

    Shockwave
    Expand Collapse
    Sr. Member

    Joined:
    Sep 19, 2009
    Messages:
    2,540
    Likes Received:
    760
    Your idea of converting the 5/8 wave to 1/2 wave should work. If you can't find a good match by moving the tap point on the current matching loop, I think the end fed half wave requires less inductance due to a lower drive impedance then the 5/8 wave. The loop length may need adjustment. Most likely shortening it although it may have enough adjustment to provide a good VSWR as it is.
     
  7. BOOTY MONSTER

    BOOTY MONSTER
    Expand Collapse
    Guest

    thanks Shockwave . the ringo has a 10 inch tuning ring on it , my current 5/8 has a 17 1/4 inch tuning ring on it . if i cant get to 1.5 vswr or lower across the chicken band then i guess ill have to try a 10 inch ring . what are your thoughts on isolating the antenna from the mast ? it'll be on 30 feet of 1 1/2 inch conduit about 2 feet in the ground and bracketed to the fascia on a very shallow pitched roof at about 22-23 feet from the ground , so the mast will extend about about 5-6 feet beyond the support point with the antenna on top of it . the entire antenna will be above the peak of the roof line .
     
  8. CDX-007

    CDX-007
    Expand Collapse
    Transducer Fanatic

    Joined:
    Jan 26, 2006
    Messages:
    707
    Likes Received:
    11
    Bummer if you have to switch to a ½ wave. I've compared a Ringo to my Penetrator and my buddy Phil sees 9-10dB less on the ringo, on his IC-756 Pro3 meter at a mere 10 miles.
    I'm not about debating theory, db loss / gain or anything else, just reporting what I've seen far too many times when trying out a ½ wave.

    Why not try guy-wire radials down to insulators and keep your 5/8 / .64?

    I'd definitely go to an Imax before I'd go to a ½ wave.
     
  9. W5LZ

    W5LZ
    Expand Collapse
    Crotchety Old Bastard

    Joined:
    Apr 8, 2005
    Messages:
    6,832
    Likes Received:
    748
    Booty',
    You are talking two different things here. One is the radiation pattern's shape with different lengths of radiators (1/4, 1/2, 5/8, etc.), or where that particular 'length' will put a signal. The second is the input impedance of the antenna, which varies depending on 'where' it's being fed, and the 'length' of the radiator used.
    Something else, or maybe just a different way of looking at it, it that all antennas have to have two 'terminals', a '+' and '-', 'hot' and 'ground', otherwise, no current flows. The typical '+' or 'hot' terminal is usually thought of as the 'whip' part of a vertical antenna, the '-' or 'ground' as radials, vehicle's body, the feed line, or some other 'thing' as the 'other half' of that antenna. (And since RF is AC, those two thingys swap around every half cycle! Fun thought, huh? And them radials DO radiate!)

    It sounds like your landlord thinks the 5/8 wave 'sticks out' too much, and would enjoy not seeing such a large antenna? Which usually means that a shorter antenna would be more desirable as far as he's concerned. That means you have the option of finding a shorter antenna that will satisfy both the landlord and the 'performance' requirement. Those two criteria are not always compatible, unfortunately. Different lengths of antennas mean different radiation patterns, where the radiated signal will end up. So, 'performance' just ain't gonna be the same between any two antenna lengths. Use whatever comes the closest to whatever you 'have' to have. And then you get to match input impedances (matching method/device) and make that 'length' resonant (load the thing). Pick a length/shape that will 'fit', then make the radio 'like' it. That's always a compromise, so pick the 'tastiest' compromise you can find.
    - 'Doc

    "You want fries with that?"
     
  10. Robb

    Robb
    Expand Collapse
    Yup

    Joined:
    Dec 18, 2008
    Messages:
    10,378
    Likes Received:
    2,134
    BootyMon:

    Since your landlord doesn't like the radial thingie goin on at the apartment; maybe it is time to improvise, adapt, and overcome? Since you have more ingenuity than duckets; perhaps you can keep the antenna length and make a loading coil that would work like the IMAX. Cheaper to make a coil than build a smaller antenna and lose efficiency - right?

    24 ft of radiator and uses the mast as a quasi-ground plane - with the right coil build is how they work - right? Copper solid strand 12 ga on the right form diameter. The only problem is - is there a formula or web page to give you the info to set you in the right direction? Sure would be an interesting project. The benefits would be comparable performance to your first 5/8 wave and keeping the landlord happy. The cost of the wire and form seem to be very small too...

    "Necessity is the mother of invention" -Plato
     
  11. Robb

    Robb
    Expand Collapse
    Yup

    Joined:
    Dec 18, 2008
    Messages:
    10,378
    Likes Received:
    2,134
    BootyMon:

    Since your landlord doesn't like the radial thingie goin on at the apartment; maybe it is time to improvise, adapt, and overcome? Since you have more ingenuity than duckets; perhaps you can keep the antenna length and make a loading coil that would work like the IMAX. Cheaper to make a coil than build a smaller antenna and lose efficiency - right?

    24 ft of radiator and uses the mast as a quasi-ground plane - with the right coil build is how they work - right? Copper solid strand 12 ga on the right form diameter. The only problem is - is there a formula or web page to give you the info to set you in the right direction? Sure would be an interesting project. The benefits would be comparable performance to your first 5/8 wave and keeping the landlord happy. The cost of the wire and form seem to be very small too...

    "Necessity is the mother of invention" -Plato
     
  12. BOOTY MONSTER

    BOOTY MONSTER
    Expand Collapse
    Guest

    damn 007 , that's very discouraging !! :(
    the height isnt whats getting his attention the most , its the ground plane elements that'll be stretching across the house . as much as i hate to say this ....... the imax 2000 may be my best option .. or the new sirio gain master . ive really enjoyed the compliments i get on my home brews performance when i had it up .ill just have to take the ground elements off and shorten it to a 1/2wgp and see if itll tune good enough 10 feet off the ground and if it will still be kind of effective......keeping in mind it will do much better at 30 feet . if it doesn't than i guess ill look for a used imax locally :( . i could still tinker with the real antenna in the back yard .... btw , guy wires would look worse than ground elements since they would be much longer . i guess another option might be to cut my four 1/4 wave elements in half and use eight 1/8 wave ground elements ..... seems to work on the sirio 2008 ..... or just four of them . that would cut its spread in half . ill ask him if that will make him happy .

    robb im not very confident in my ability to duplicate the matching network on a imax . it seems to be a coil inside a coil and apparently a lot of engineers arnt really sure whats going on with it . the new sirio antenna is (AFAIK) the first/only 5/8 11 cb antenna to hit the market without ground elements . time will tell if its as good or better or lesser performing than the imax . but yea , the less money i have to spend the better .
    thanks guys ;)
     
    #12 BOOTY MONSTER, Aug 25, 2010
    Last edited by a moderator: Aug 25, 2010
  13. Highlander_821

    Highlander_821
    Expand Collapse
    Amour d'Ecosse

    Joined:
    Apr 2, 2005
    Messages:
    1,090
    Likes Received:
    20
    I think I would put up an Imax rather than butcher your 5/8 homebrew., That would be a shame, especially if you couldn't get it to work. The Imax might be a little step down from the homebrew, but I think it will do quite a bit better than the 1/2 wave hack that you're thinking about doing.
     
  14. HomerBB

    HomerBB
    Expand Collapse
    Sr. Member

    Joined:
    Jan 4, 2009
    Messages:
    2,868
    Likes Received:
    625
    What Robb is saying is to forget about the GP radials altogether. Try a loading coil at the base of the antenna, and instead of a GP radial system, use the metal mast the antenna is mounted to for your counterpoise. This you would do by loading the antenna at the point where the mast and antenna meet through a coil made of 12 or 10 gauge wire.

    I suggest a coil of about 1 1/2" inside diameter with around 9 - 10 wraps. the coils having a space between them of the same distance as the diameter of the wire itself. Top of the coil to the upper aerial, bottom of the coil to the mast. Coax shield to the mast, and the coax center conductor tapped to the coil for best match (probably around the second to fourth coil from the bottom). Mind you, this is only an experiment as suggested, and anyone who knows more than I do can correct anything I've suggested. It may turn into a solution. shrug

    (BTW, a coil of the dimensions I suggested has worked successfully for me on at least two 5/8 homebrew antennas.)
     
    1 person likes this.
  15. BOOTY MONSTER

    BOOTY MONSTER
    Expand Collapse
    Guest

    thanks highlander and homer . i wouldn't really be butchering the 5/8 , just cutting the ground elements in half and most likely retuning the antenna .

    homer , so you're saying the coil you're describing would work better than my 17 inch diameter maco type ring for tuning when just using the mast for a counter poise /ground element ? when you used your described coil on your home brews did you try it as youre suggesting with just the mast as a ground element ?

    you got the hamster in my head spinning its wheel now ;)
     

Share This Page