RadCom Basics May 2022, Edition 28

RadCom Basics 25 er than dBd measurements. This is because dBd starts at zero when the gain matches a dipole (which has 2.15 dBi of gain from the start). Just be careful when comparing antenna gain and make sure you’re comparing apples with apples! Collinear Collinear (aka “white stick”) anten - nas are the mainstay of the VHF/ UHF bands and a popular choice. They are vertically polarised, quite discreet and typically cover more than one band at once (typical- ly 2m/70cm) and are omni-direc - tional. The lack of directionality is an advantage in one way, because it means you don’t need to think about a rotator. There’s a convention that says if you’re using FM then the antenna should be vertically polarised and if using SSB then it should be horizon- Figure 2: My PowABeam 15 element Yagi for 70cm [2] offers 16.7 dBi (or 14.5 dBd) gain. I don’t have this in- stalled permanently, instead I put it up temporarily for contests and take it out portable. Figure 3: My Diamond V2000 collin- ear on the roof – this covers three bands in one (6m/2m/70cm).