20/30/40m trapped dipole

One of the aims of SOTA is to walk in the nature.

So, a light backpack it’s a must !

One the first opportunity I bought a Montain Topper Radio, MTR-3B wich is a 3 band HF (20/30/40 m ), which weights 124 gr.

Because the MTR doesn’t have an ATU or a SWR meter and I don’t want to carry anyone of those, I decided to make an antenna that fit the objective: Been light!

The search for such antenna endup with the trapped dipole or the linked dipole.

Well…I would have quick band changing: The trapped dipole is the way to go!

Searching for antenna traps was an easy one: Sotabeams pico traps!

When they arrived it’s clear that they deliver. Easy to build and tune. Very light weight: 5 gr each!

So a traped dipole was made. On one sunny sunday João, CT7ABE helped to make all measurements at the local public park. After that, all the welding was redone and a liquid rubber coating was applied.

Another set of tests confirm: The antenna was ready to go!

I used a 6m fishing pole but the last meter (tip) wasn’t used because it’s too thin and doesn’t stand the weight.

The 10.45m is an arbitrary dimension, recognising that the 45 degree angle at the  apex wouldn’t be achieved

The details are as follow:

 

dipolo_final

Trapped dipole (final)

 

Dimensoes

Dimensions

 

Picotrap_2

Trap (top)

Picotrap_1

Trap (side view)

 

Picotrap_3

Trap (bottom)

 

Centro_dipolo_3

Center dipole

 

Centro_dipolo_2

Center dipole

 

Centro__dipolo_1

Center dipole

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5 comments

  1. Rienus · March 1, 2016

    Hello Pedro, this is exactly the solution I was looking for. The combination 20, 30 and 40 meter are the best choice in my opinion. And no ATU needed..! Tnx for the info and good luck, good SOTA..

    Like

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  4. Hans PA1ALV · February 15

    Hello Pedro, can you tell me what wire you use for your antenna? I have some thin teflon wire, but that’s pretty stiff.
    Sotabeams sells also antenna wire.
    I ordered some toroids and capacitors and some wire to wrap.
    I think this antenna could be a good solution instead of 3x separate resonant dipole’s for 20, 30 and 40 meters.
    73″ Hans, PA1ALV

    Like

    • Pedro, CT1DBS/CU3HF · February 15

      Hi Hans

      I use Sotabeams wire. It’s the best compromise wire that I found, when looking into mechanical resistance, flexibility and wheight.
      the one is at http://www.sotabeams.co.uk/antenna-wire-lightweight-100m/ (yellow).
      This is neat solution. The Sotabeams pico traps are awesome!
      Please note that I use always QRP in SOTA activation.

      This is the antenna that I use when travel abroad, namely to CU2 or CU3 (Azores). This antenna is the one that had used during EUNA/ZL QSO party. With 5 w, 2 QSo with VK, one is a S2S ! 🙂

      Vy 73

      Pedro, CT1DBS/CU3HF

      Like

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