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Antenna Project Success!

Discussion in 'Home Brew' started by T23, Nov 17, 2010.

  1. T23

    T23 Active Member

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  2. Highlander_821

    Highlander_821 Amour d'Ecosse

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    So what did you end up doing for a counterpoise / ground plane? You can usually adjust the angle between any radial elements and the driven element to get the impedance closer to 50 ohms. You might also need to do some trimming/adding of length, mainly to the radiator.
     
  3. Robb

    Robb Yup

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    Congrats!

    If you could take a full-size picture and post it, you can get some ideas to really dial it in.
     
  4. 15minigrass

    15minigrass Active Member

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    You will also need the extra 6 inches to make it 108" long. What I also did was wrap some stiff wires to the top of the 102". and yes you do need the ground plain to bring down your SWR.

    Hereʻs how I have mines.... Yes only 1 ground plane is enough. Iʻll get some close ups of the box.
    [​IMG]

    [​IMG]

    This is before w/2 GP
    [​IMG]
     
  5. 15minigrass

    15minigrass Active Member

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    It works. I have talked to AUS and Stateʻs with this and my P/T Cobra 146GTL!!!
     
  6. T23

    T23 Active Member

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    I had to make some adjustments already to it before I finished, like for example I had to isolate the two radiator clamps that hold the PVC pipe up from the all-thread by wrapping it with electrical tape, The all-thread is isolated from the ground plain with rubber washers and the center wire of the coax is soldered to a washer that is bolted to the all-thread, the wire I am using for the actual antenna is thick copper wire, it connects to the all-thread by being set between two washers and 2 nuts on the all-thread, I had originally planned to use plumbers tape to isolate the all-thread from its base but found it was unnecessary... My receive GREATLY improved, I think the old roberts rcb-11's audio amp is dieing... When I was testing the antenna for the first time I used this radio and my audio keep getting quieter and quieter and going in and out, but when I connected my other test/mobile rig my receive audio was great.


    I'll see if I can get some pics up soon.

    Its nothing to drool over by no means:laugh::LOL:

    T23
     
  7. Robb

    Robb Yup

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    Have you got the SWR down below 2? Should be tunable to 1.5; I would shoot for that. I wouldn't even talk on it until it was 2 or lower. Could damage the radio with too much power being reflected back into the final transistors by heating them up.

    Is that aluminum foil around the center box; or duct tape?
    Hope it's duct tape . . .

    I would take the tape off and just put a cover on the box.
    TO get the SWR lower; the radials should be at a 45 degree angle.
    Then use the SWR meter to find out which channel has the lowest SWR. Check it at ch 1, 20, and 40. If it is low on ch 1 and high on channel 40; then the vertical radiator is too long. If it is low on ch 40 and high on ch 1; then it is too short. Ch 20 is the preferred spot to get the lowest SWR for the regular 40 ch CB radio. If you have that; you are good to go.
     
  8. T23

    T23 Active Member

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    :LOL:

    Yes, I was aiming for 1.5, I think my ground plain is too small...But I don't know, hey just for laughs my very fist antenna (or antenna attempt I should say :laugh: ) I built a dipole antenna outa garbage... and the SWR reading was off the meter!


    T23
     
  9. Robb

    Robb Yup

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    I'm not laughing at you or your antenna effort. It's just fine. Getting what you have to be functional is only a few steps away. Keep workin at it. Remember, that the vertical and the radials should be 102 in in length. Once the radials are at a 45 degree downslope; then tune the vertical for fine tune 1.5 SWR.
    (y)
     
  10. Moleculo

    Moleculo Administrator
    Staff Member

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    Try sloping the radials down more toward 45 degrees and see what that does to your SWR readings. It should help quite a bit.
     
  11. i found these links to be very helpful when trying to understand what a proper ground plane for a 1/4 WGP is .

    Antenna Notes

    Antenna Notes

    Antenna Notes

    dont forget a coax choke ;)
     
  12. Robb

    Robb Yup

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    Can you remember how you did it?
     
  13. 15minigrass

    15minigrass Active Member

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    Hey T23 parts list.

    -Electric square outlet(conduit) type box like I have(metal)
    -Gumball Mount
    -1 SS 102" whip w/PB Spring
    -Another 102 whip for the ground radials
    -1 steel conduit fitting(Ones used to run the wires to the box) or another Gumball mount but ground the middle terminal to the housing

    http://www.custom-counter.com/resim...%20fixture%20%BB%20pictures%20photos%20images
     
  14. mackmobile43

    mackmobile43 Jock Supporter

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    Sorry but I would not recommend a gumball mount to my worst enemy, they have a history of failure when a long or heavy wind load antenna is used.
     
  15. T23

    T23 Active Member

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    What I have used is:

    Half inch PVC pipe.

    A camera tripod ( the first one failed, the threded hole where the camera mount would go stripped out.... ) But I found another one, I am thinking about ditching the tripod and mounting it on the roof later when I am finished.

    A '5 piece of metric all-thread.

    Two rubber washers.

    About a 5' in diameter disk, ( groundplane )

    Four metal washers.

    Three nuts ( not the kind you eat:D )

    Two radiator clamps ( the ones you tighten a screw to clamp )

    Some yellow electrical tape ( to isolate the radiator clamps from the all-thread.

    A piece of un-insulated heavy grade house electrical wire.


    T23
     

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