144 MHz
Dipole and Balun



Installing the dipole and balun in one heavy-duty weather protected PVC housing with Teflon(R) 7/16 connector and stainless steel eye bolts. Fixing the 12,7mm radiator with 2x clamps.




Drilling 18mm in the center en 4mm for the bolts (size of 7/16) in a aluminium plate and bending the plate 90 degrees.

Grounding the two 75 ohm λ/4 lines on the far side leads to the DK7ZB Style 50 to 28 ohms Quarter Wave Line Match.

  Marking the holes

The cabinet is 3mm thick therefore a 3mm spacer is placed under the bended plate to mark the drilling holes on the outer side of the cabinet.

10mm center space and inserting parafill rope. Drilling the dipole connection holes.


Dipole cabinet ready for installation on the boom.

The green ground coax is much too heavy, instead I have 2YCCY 1,0/6,5-75 in stock but the velocity is unknown. It looks Polyethylene (PE=2.3) but I am not certain. It can be shown that the velocity factor of the cable is the reciprocal of the square root of the dielectric constant.



I do have a variety of coax with unknown dielectrics. The Foam polyethylene coax-7 has a dielectric constant of 1.5. The velocity factor is determined normaly by the dielectric of the coaxial cable, but can also be found to measure 1meter of cable and look at the outcome.


DK7ZB match

This Symmetrising Member transforms from 50 to 28 ohms as shown above and symmetrises. It is a two-in-one.

Basic Scheme of Quarter Wave 50 to 28 ohms Transformation Line Picture from DG7YBN website


Narrow adhesive copper band wrap around the coax. Flexible copper wire and soldering the waterproof cabinetcover (with ring) onto the boom

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