10m – 20m Trap Dipole

Want to operate on 10 and 20 meters in limited space?  Build yourself a 10m – 20m trap dipole antenna.  The antenna requires about 25’ of horizontal space and works well at heights as low as 20’.  My friend Barry, KI4PMI, and I  built one of these antennas and it performed well.  This is a good FIELD DAY antenna that can be used with tripod mounts and push-up masts.

If you are interested in the tripod mounts, contact John Baranosky for details.

BARANS SURPLUS
(570) 693-1795

Email: BARANOSKYBUNCH@AOL.COM

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An EZNEC model of the antenna is available at the link below.

10m – 20m trap dipole EZNEC model

Note:  Take a look at the article on modeling coax traps.

Figure-1

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Use the free coax trap design tool (courtesy of VE6YP) to get the specs for winding the traps.  To minimize trap losses, pick a resonant frequency just below the 10m band (~28.0 MHz). You will probably want to use either RG-58 or RG-59 to wind the traps.  Schedule 40 PVC pipe is relatively inexpensive and makes a good form for the traps. 

Note:  Tune the 10m portion of the antenna first.  Attach the traps and adjust the radiator lengths for the best SWR curve.  Then attach the 20m sections and tune the 20m band by adjusting the radiator lengths for the best SWR curve.

The model predicted SWR curve and the measured  SWR curve for the 10m band are included below.  An AIM-4170C was used to analyze the antenna.  The measured 10m SWR curve was much better than the predicted SWR curve.

Graph-1imageGraph-2 

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The model predicted SWR curve and the measured  SWR curve for the 20m band are included below.  The measured 20m SWR curve was approximately the same as the predicted SWR curve.

Graph-3

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Graph-4

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The EZNEC predicted radiation patterns for the 10m and 20m bands are included below.  The predictions indicate good performance for both bands.

Graph-5

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Graph-6

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