4 el. 40m Yagi
40 meter 4 element beam Yagi (7 MHz) DXBeam (Ref. DXM40-4)
40 meter 4 element beam Yagi (7 MHz).
Shortened element with high-Q loading coils.
Boom made from 60 to 50mm tube.
Elements made from 35 to 12mm tube.
Insulating Guying provided for boom and elements (longevity more than 25 years): see pictures and remarks below.
• Forward gain in free space (dBi): 6.8
• F/B ratio (dB): 20
• Frequency coverage (MHz): 7.000 - 7.200 MHz
• Bandwidth @ 1.5 VSWR (kHz): 195
• Feed impedance (ohms): 50
• Power handling (kW): 5
• Longest element (m)/(ft): 13.40/44.1
• Boom length (m)/(ft): 12.35/40.5
• Turning radius (m)/(ft): 9/29.5
• Weight (kg)/(lb): 47.5/104.7
• Wind survival (km/h)/(mph): 125/77.7
• Standard Mast size (mm)/(inch): 50/2 (55/2.25 or 60/2.50 optional at no extra cost).
This 4 element 40m Yagi is based on the same concept as the 3 element "short boom" version, i.e. without log-periodic cells, but on a boom length of 12.35m (40.5ft), the same length as the existing 40m "long boom" 3-el monobander (DXM40-3) from DXBeam. The computer model for this antenna was devised almost 5 years ago by F6ARC, but prior to marketing, this new model has been successfully used by Gildas, F4HQZ (ex F/TU5KG), since Feb. 2015.
Boom guy set
1 - "Over the boom" guy set with vertical support included : Due to the weight and size of the 4 element 40m beam, an "over the boom" guy set providing vertical support is now included. The set consists of a reinforced tube (1m long, 50mm in diameter and 5mm wall thickness) to which the 7.5mm non-metallic tensioning cable (CU1) attaches. (see pictures above).
Tensioning is done whilst the antenna is at ground level, ie. prior to its installation on the mast/tower.
2 - Lateral guying to the boom recommended : Should you live in a region where wind, snow or ice are common place, we recommend adding lateral guying to the boom. This addition could also be of interest to those who have towers without tower tram systems. It prevents the boom from being subjected to unnecessary mechanical stress during its installation. If you choose to add this diamond shaped guying yourself, be sure to do so using non-metallic cables.
>> Lateral guying to the boom kit
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).