3 el. 40m Yagi short boom

40m rotary dipole (7 MHz).
Shortened element with high-Q loading coils PTFE insulated and weatherproof.
Element made from 35 to 12mm tube.
Insulating Guying provided (see below).

40 meter 3 element beam Yagi (7 MHz) short boom.
Shortened element with high-Q loading coils PTFE insulated and weatherproof.
Boom made from 55 and 50mm tube.
Elements made from 35 to 12mm tube.
Insulating Guying provided for boom and elements (longevity more than 25 years): see below.

Introduction

Unlike a standard 3 element Yagi with reflector, driven and director elements, this antenna is based on a different concept. It significantly improves the performance of the aerial, such as forward gain and front-to-back ratio, and in addition considerably increases the bandwidth. DXBeam preferred not use log-cell driven elements which whilst they improve SWR at band edges, do not maintain constant gain and front-to-back ratio throughout the entire 40m band. Note that this concept has nothing to do with a 3 element OWA-Yagi.

This antenna has been used by F2DX since November 2013, for almost exclusively DX trafic. F2DX has worked more than 320 DXCC countries on 40m and uses also, as a comparison antenna, a 4-square with 512 radials. Except for a few contacts, the DXM40-3sb installed at 20 m above ground has always been 1 to 2 points higher than the 4-square.

Specifications

• Forward gain in free space (dBi): 5.7

• F/B ratio (dB): 29

• Frequency coverage (MHz): 7.000 - 7.200 MHz

• Bandwidth @ 1.5 VSWR (kHz): 150

• Feed impedance (ohms): 50

• Power handling (kW): 5

• Longest element (m)/(ft): 13.34/43.8

• Boom length (m)/(ft): 6.50/21.3

• Turning radius (m)/(ft): 7.47/24.5

• Weight (kg)/(lb): 34/75

• Wind survival (km/h)/(mph): 130/80.8

• Standard Mast size (mm)/(inch): 50/2 (55/2.25 or 60/2.50 optional at no extra cost).

Greases supplied

2 kinds of grease are supplied with your antenna:

• Aluminum contact grease: Professional grease containing 30% aluminum particles, recommended for the assembly of aluminum antenna tubes. Prevents binding, corrosion and the formation of aluminum oxide, and allows easy dismantling of antennas after several years.

• Copper conductive grease: Professional conductive grease with a copper base, recommended for all hardware requiring a sound and lasting electrical contact. Prevents oxydisation, damp ingress, and limits chemical reaction between stainless steel and aluminum.

Balun or no Balun ?

• This antenna does not require any balun.

• To avoid having stray current on the braid of a coaxial cable (often the cause of RF and/or TVI/BCI), you can make your own 1:1 choke balun with coaxial cable. Explanations are provided with antenna assembly instructions. (See also our F.A.Q).