Add-On 40m Dipole Option (1000 W.)


NOW Available, Assembled or Kit Form



Spiderbeam's  NEW  Add-On 40m Dipole for its family of hf Yagi's.

Source:  Spiderbeam GmbH


In the drawing above:

  • Everything in BLUE is part of the original Yagi.  
  • Everything in RED is part of the 40m Add-On Dipole.  
    • The second balun is optional (see below).



Sorry, it is nearly impossible to obtain a good photo from the ground.  I have highlighted the 40m Add-On bits.  The photo above shows the option of having a second balun.  Here the dipole is below the boom.   When you use only one balun, the dipole is above the boom.


The drawings (below) show the Vertical-Plane and Horizontal-Plane of the Dipole's Radiation Pattern:

Source: Spiderbeam GmbH


The graph above shows the SWR curve across the 40m band.


The dipole is rotated 90 degrees to avoid interaction with the higher bands.

  • The two tiny loading coils weigh just 40g (1.4 oz.) each and are rated at 1000w SSB/CW.
  • The extensions to the boom are made of segment no. 12 of the Spiderbeam 12m telescoping fiberglass pole and have an average diameter of 10mm (~3/8").
  • The dipole wire is CQ-532, the same wire as used in the wire elements of the Yagi.
  • The capacity-hat wires off the tips of the extensions is made of CQ-534 wire which is much thinner. This is no problem because very little current is flowing in that part of the antenna and this helps reduce the weight on the outer ends of the boom.
  • The entire dipole weighs just under 500g, or about 1 pound (not including the balun).


The dipole is rated for 1kW SSB and CW, and its impedance is about 40 Ohms and the SWR is under 2:1 from 7000 - 7200 kHz, and is still useful at 7300 kHz.


A critical eye will notice that the dipole is not completely symmetrical.  The capacity-hat wires are of different size.  This was necessary to avoid interaction on 10m and is non-critical to performance on 40m.


The dipole will work with the Portable and/or Heavy Duty versions of the Spiderbeam, regardless of whether they are 3-Band or 5-Band versions.  IMPORTANT: You must specify which version of the beam you have because the clamps and tube-size are different, depending on version.


Of course the turning radius of the antenna is slightly longer - but the difference is less than one meter (about 30").



The dipole will work with:

  • 3-Band Spiderbeam Yagi  (Portable and HD versions)
  • 5-Band vSpiderbeam Yagi  (Portable and HD Versions)  
  • Existing, already installed Spiderbeam Yagis.


  • NO, it will not work with the Spiderbeam WARC Yagis.
  • NO, it will NOT work with Yagis or Beams from other manufacturers!


The original beam was constructed such that its two extension tubes slip down inside of the ends of the Heavy Duty Spiderbeam Yagi's boom tubes.  The extension tube is simply the top segment of the Spiderbeam 12m telescoping fiberglass pole, with a few layers of heat-shrink tubing (abt. 15" long) over the bottom end.  This is built up in layers until it fits snugly inside of the ends of the beam's boom tubes.  The thin extensions extend about 83cm (~33 in.) beyond the current tips of the boom.


Later versions simply added another tube to each end of the boom.

There is also  a version for the portable Yagis.  


1 or 2 Baluns?

The user may decide him-herself whether to attach the dipole to the same balun as the other elements or to use a separate balun.  The separate balun is identical to the original balun. 

When attaching the 40m dipole to the same balun as the Yagi elements, the front/side ratio is reduced slightly on other bands, especially on 15m.


Advantage of two baluns: 

  • You can run two stations at the same time, one on the beam, the other on the dipole.
  • Does not degrade the front-to-side ratio on the higher bands.  With two baluns, it has slightly better front-to-side ratio on 20 and 10m, and considerably beter front-to-side ratio on the 15m band because when running with a single balun, it is an excellent 15m RX antenna.

Disadvantages of two baluns:

  • Higher cost (for the second balun and coaxial feedline)

The normal front-to-back ratio is not affected by the addition of either feed method.


The 40m dipole is a standard Add-On product which may be added to any version of the Spiderbeam Yagi's at any time.  It is listed on the Yagi page of Spiderbeam's two web sites.


NOTE:  When using the add-on 40m dipole and the add-on 30m dipole together with the Spiderbeam, you MUST use a separate BALUN and feedline for the two dipoles. 

Best case, mount the BALUN connecting both dipoles about 1 meter (3.3 ft.) above the BALUN connecting the higher band driven elements.  This enables greater separation between the wires of the two dipoles.



DISCLAIMER:   All of the above is subject to possible changes.


40m Dipole Specifications - ENGLISH
This document shows the Specs.
40m Dipol spec EN.pdf
PDF-Dokument [648.4 KB]
40m Dipol Spezifikationen - GERMAN
40m Dipol spec DE.pdf
PDF-Dokument [649.8 KB]


  • The 40m Add-On Dipole is now only available in the "Assembled" version. 

  • The "Kit" version is no longer available.


40m Dipol Bauanleitung - GERMAN
(English Version in preparation) this file shows in detail, how to build the 40m Add-On Dipole Kit
40m Dipol Anleitung.pdf
PDF-Dokument [1.3 MB]
40m Dipole Construction Guide - ENGLISH (A4)
This English version of the construction is for printing on A4 size paper.
40m Dipol Construction Guide-A4.pdf
PDF-Dokument [838.6 KB]
40m Dipole Construction Guide - ENGLISH (Letter)
This English version of the construction is for printing on Letter size paper.
40m Dipol Construction Guide-Letter.pdf
PDF-Dokument [485.2 KB]
Drawings with Dimensions for 40m Add-On Dipole
This drawing shows the exact dimensions of the Dipole at different stages of construction. The primary radiator (CQ-534) should be very close (each dimension shown might be one cm off - not critical -). Final tuning is performed on the capacity loading wires. (Date: 18-APR-2019)
Measuring 40m Dipole Components.pdf
PDF-Dokument [268.3 KB]