Basic ½ Wave Dipole Antenna

Presentation By: Rodney Davis W3LDR and Chris Mabry KF5QIS

Lubbock Amateur Radio Club

The ½ WaveDipole Antenna

Benefits:

Easy to build

2.1 dBi Gain Typical

Direct Coax Feed

Portable or Fixed Location Use

Great for State Side and DX Contacts

Dipole Fundamentals

A dipole is an Antenna composed of a single radiating element split into 2 sections. Not necessarily equal lengths. (However for Our Build it WILL Be)

The RF power is feed into the split

Radiators DO NOT Have to be Straight

The ½ Wave Dipole

The length is approximately ½ wave

Self impedance is 40-70 ohms (Considered a good match to coax)

Directivity 2.1 dBi

SWR Bandwidth is approx 5% of tuned Frequency

½ Wave Dipole Typical OAL

Length per Band

How to Calculate Length of Antenna

Simply Divide 468/Frequency = Total Wire Length

Total Wire Length / 2 = Each Dipole Leg Length

468 / 7.190mHz = 65.09ft 65.09 / 2= 32.55ft

Add 1ft Extra wire to Each Leg for Tuning approx 331/2 ft

Wire Considerations

Solid vs. Stranded

Solid Can and Usually will BREAK due to winds and movement. Subject to Corrosion.

Stranded More Forgiving and Last MUCH Longer

Most Popular wire size is 12-14 ga. Insulated Stranded

SuggestedBuild Materials

14ga Insulated Stranded Wire

2 – Insulators (PVC, Plastic, Ceramic or Glass)

Dacron or Quality UV Resistant Rope

Suggested Build Materials for

CenterSO 239 Bulkhead Connector and Small Piece of Coax

2” PVC 4-6” Long (Longer if Building Choke Balun)

2” PVC Cap

2” PVC Plug

2” PVC Coupler

¼” Stainless Eye Bolt x 3

#8 Stainless Machine Screws x2 1 ½” Long, 2 - #8 Nuts, 4 - #8 Washers and 2 - #8 wing nuts (All Stainless)

Dipole InstallationA Dipole may be erected between 2 supports or with 1 support

A Dipole using one support is known as an Inverted-V

The legs of the Dipole may also be bent to form a Inverted U. The bend should be at least half way to the end of the wire.

NOW

WITH THE BUILD