Add-On 40m Dipole Option

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

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).


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's 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.


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


Current Status on the 40m Add-On Dipole Option:

Spiderbeam is awaiting a mass  production of coil forms for building the two tiny loading coils.
They must first build a mold and then the forms.

They originally had 30 pieces built on a 3D printer...which was very expensive.
This enabled them to build 15  40m dipoles.
All 15 went to the WRTC-2018 antenna team, who tested 15 setups in June (2017).

Unfortunately they don't expect to receive any coil forms until late September, so availability of the dipole add-on is projected to be in October 2017.  All other material is standard Spiderbeam components that are always in stock. 

The dipole itself will work with either the 3-Band version or 5-Band version of the Spiderbeam Yagi.  

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 (~30 in.) beyond the current tips of the boom.

There will also be a version for the portable Yagis.  Most likely Spiderbeam will just stock the version for the HD and the Portable version will be the HD version of the dipole plus enough heat-shrink tubing to add 2 more layers of tubing around the lower 15 inches, such that it then fits snugly inside of the wider tubes of the portable Yagi.

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. 

  • Advantage of two baluns: 
    • You can run two stations at the same time, one on the beam, the other on the dipole.
    • Slightly better front-to-side ratio on the high bands than when running with a single balun.
  • Disadvantages of two baluns:
    • Higher cost (for the second balun and coaxial feedline)
    • Slightly less front-to-side rejection since the dipole picks up a bit of signal off the side of the beam

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


The 40m dipole will become a standard Add-On product which may be added to any version of the Spiderbeam Yagi's at any time.  When it becomes available, it will be listed on the Yagi page of Spiderbeam's two web sites.


It is fine to purchase the beam now and the add-on later when it becomes available.

There is no additional work required if you purchase the dipole later, other than lowering the antenna too do the work, then raising it again.

There is no advantage in waiting to purchase the beam.

ESPECIALLY if you wish to purchase a fully assembled beam, it is better to do that now.
We are currently in the July/Aug/Early-Sep  European summer vacation slump and the boys at the factory have time to build beams.  
In October they will be back in full swing so the delay will likely be a bit longer, unless you order the beam in its Kit version.