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Thread: 10/20/40 Trap Dipole

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  1. #1
    Join Date
    Jun 2011
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    Default 10/20/40 Trap Dipole

    I am only interested in the 10, 20, and 40 meter bands and want to make a dipole for the 3 bands. I know I need traps but looking for either a design or design software to accomplish my goal. Anyone know where I can find either a design or software that runs on Win-7.

  2. #2

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    What about a multi-band or "fan" dipole? I am using one now for 15-10m and have had no problems.

  3. #3
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    It's not so much about "design software" as you will require a grid dip meter to check the resonant
    frequency of the trap. Software will usually only get you in the ballpark of things.

    However this design might be of interest.





    "To delete 80 meters, simply omit the 40 meter traps and everything after them, placing the end insulators where the 40 meter traps used to be, and you'll have a 10/15/20/30/40 antenna. The dimensions of the remainder of the antenna will be unaffected except that the 40 meter segment lengths might need to be lengthened slightly due to the removal of the end loading provided by the 40 meter traps.

    Similarly, to delete both 80 and 40 meters simply omit the 30 meter traps and everything after them, placing the end insulators where the 30 meter traps used to be, and you'll have a 10/15/20/30 antenna. The dimensions of the remainder of the antenna will be unaffected except that the 30 meter segment lengths might need to be lengthened slightly due to the removal of the end loading provided by the 30 meter traps. "


    The complete article is here: http://degood.org/coaxtrap/
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    73 de Charles - KC8VWM
    North American QRP CW Club #3159, SKCC# 5752

  4. #4
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  5. #5

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    Building traps can be an educational excersize that's fun and results in a working antenna; but I just buy them from Unadilla because I can buy them cheaper than making them.

    And since I'm cheap, I always go for that if I can. The Unadilla 10m and 20m traps work fine, are very strong, and have been around about as long as I have (a long time), and they can handle legal limit power. Some coaxial traps cannot unless they're made of the right coax and done well.

    Sorry, should have included a link to the Unadilla-Reyco traps: http://www.unadilla.com/?cat=8
    What if soy milk is just regular milk introducing itself in Spanish?

  6. #6
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    Quote Originally Posted by WB2WIK View Post
    Building traps can be an educational excersize that's fun and results in a working antenna; but I just buy them from Unadilla because I can buy them cheaper than making them.
    Well thanks for the link and tip. I did check the link and $50 for a trap seems pretty steep.

  7. #7
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    Quote Originally Posted by N4ERZ View Post
    What about a multi-band or "fan" dipole? I am using one now for 15-10m and have had no problems.
    Actually I am seriously considering just that. Have not read anything negative about fan dipoles.

  8. #8

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    Quote Originally Posted by KF5LJW View Post
    Actually I am seriously considering just that. Have not read anything negative about fan dipoles.
    A couple insulators, a bunch of wire (take your pick) and a few homemade PVC spacers and you will be set. Rather inexpensive and not too tough to build

  9. #9
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    OK let me ask this. Can they be on an Inverted V config, so the 10 meter would have the greatest angle downward, and 40 meter the least?

    I plan to mount a mast on my home chimney and anchor the wires to the ridge line of the roof.

  10. #10
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    I have built several sets of traps over the years. They are not hard to build and have worked well for me. One thoughts are keep them light. I have used pvc. The ones I liked the best were made of 1 inch thin wall pvc. The type used for the drain on a kitchen sink with no caps on the ends. I simply drilled a hole in the ends and used a stainless steel 10-32 nut and bolt to attach the coil winding and antenna wire. I used no.14 stranded spaced with a braided nylon cord. I am planning on building some in the near future that uses no. 12 or 14 solid house wire with the insulation on to provide spacing and insulation.
    The nicest looking used schedule 40 2 inch PVC with caps and eye bolts. They weighed A LOT cost more than the simpler ones and I just never liked them as much as the simpler, lighter ones.
    If you choose not to use store bought capacitors. I used duel sided PCB. The capacitance can be tested or found on line. Some I just bought tested out to be 18Pf/ square inch. It has a high dielectric and if you etch the edge back a bit it can handle legal limit. I have used coax as a capacitor but found it to be less stable in changing weather conditions.
    I used the radio transmitter with a dummy load and a watt meter to determine resonance. Turn your output as low as possible and wind or unwind the coil until you have your trap in tune.
    I think you will have a lot of fun building your own and when you are finished it always made me happy to look up at the antenna.
    Joe

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