Exploring Antennas

Van Warren

AE5CC

Exploring Antennas: Pattern

• D esign

• S imulate

• M easure

• R efine

Exploring Antennas: Rule 1

• Don’t reinvent the wheel.

Explore and understand successful designs before

inventing new ones.

Exploring Antennas: 2m

Middle of band is 146 MHz

Middle of CW band is 144.05 MHz

Single Most Important Parameter:

Wavelength

Exploring Antennas: 2m

Middle of band is 146 MHz

146 MHz = 2.053 meters = 6.7 feet = 80.83 inches

Full Wavelength

Exploring Antennas: 2mGeneral Purpose 2m Antenna in free space.

Exploring Antennas: 2mGeneral Purpose 2m Antenna with Ground Plane (-5 Hz shift)

Exploring Antennas: 2mGeneral Purpose Ground Plane Antenna.

Exploring Antennas: 2mGeneral Purpose Antenna at 144 MHz In Free Space

Exploring Antennas: 2mGeneral Purpose Antenna with Ground Plane at 144 MHz

Exploring Antennas: 2mSame Antenna at 900 MHz (33 cm band).

Exploring Antennas: Loops

•Now duplicate argument using tetrahedral geometry reasoning from the simplex argument and minimal materials and tesselation of sphere for balloon borne 2m antenna. Also reduce to ¼ wave and compare gain with full wavelength cases.

Exploring Antennas: Loops

• Design Antenna

• Simulate Antenna

• Measure Antenna

• Improve

Design Antenna: Requirements

• Use 42 AWG • DX: 1 – 1000 MHz• TX: 80 – 2m 50 watts• Aesthetic, preferably invisible• Low Lightning Hazard• Low Structural Hazard• Easily Relocated• Inexpensive

Design First Pass: Wire Loop

• Materials 42 AWG • DX: 1 – 1000 MHz• TX: 80 – 2m

• Aesthetic, preferably invisible • Low Lightning Hazard • Low Structural Hazard • Easily Relocated • Inexpensive

0.0025 in diameter

Design Pass: Vary Parameters

Observe Effects of:

• Wire Diameter Variation

• Frequency Variation

• Loop Geometry Variation– add recursive elements– in plane/out of plane elements

- Start: 42 AWG - 0.00125” radius

- 160, 80, 40, 20, 10, 6, 2, 0.7, 0.3 meters- 1.9, 3.5, 7, 14, 28, 50, 144, 420, 902 MHz

Total gain @ 20 MHz

Results suggest a wire loopCan be “aimed” by simplyChanging the feed point.

Suggests a new radar antenna.Stationary loop, moving feed point.

What is radiative efficiency?

“Large” Circular loop has relativelyflat frequency response,but surprisingly, high directionality!(front/side ratio)This borders on discovery!

Compare with microphone gain patternsand yagi’s or “beam” antennas.

Need a program that will let me preprogram a series of mouse positions, clicks and key presses, to create animations of the gain patterns of these loop antennas.

These are necessary and wonderful animations.