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The CP22E is a 2-meter monoband, 2-5/8 wavelength groundplane antenna, optimized for the U.S. amateur band. Made from heavy-duty aluminum, the CP22E is easily assembled, yielding excellent performance with 6.5 dB gain over a 1/2 wave dipole.” Emphasis added on specifications that don’t stand up to analysis or Diamond’s own measurements. This one blemish doesn’t spoil the positive attributes. Let’s have a closer look at the CP22E to see why. Sleek look The Diamond CP22E maintains a slender look with relatively thin aluminum elements. Here is a view atop an 8 foot fiber glass pole and speaker stand. As Diamond’s description attests, the CP22E electrical design nurtures antenna currents similar to that of a properly spaced vertical collinear 2 bay antenna. Figure 3 showcases a simulation wire model of the CP22E. CP22E wire model with currents Fig. 3 – CP22E wire model with currents Key features include from top to bottom: Top element made of ~1/4 inch diameter aluminum tube with length approximately 5/8 wavelength at 146 MHz. Phasing coil ~1.5 inches in length with an approximate 0.7 uH value for properly phasing the upper and lower elements. Think of this inductor as “consuming” most of the middle half-wave of out of phase antenna current leaving only the upper and lower current peaks to radiate in phase. Lower element made of 1/2 inch diameter aluminum tube with length approximately 3/4 wavelength at 146 MHz. This length includes a 5/8 wavelength component along with an extra 1/8 wavelength section to give a matching section a better impedance to chew on. Matching section with the high-pass characteristics of a dc open circuit between the antenna RF connector center conductor and the antenna elements plus a short circuit between antenna elements and mount/coax shield. * WX resistant metal treatment on the two aluminum tube elements with an electrically insulating coating. Three decoupling radials of 20.25 inches in length. The currents shown in the right side of figure 3 reveal how the designers successfully manipulate the phasing to produce two prominent in-phase current peaks with near ideal vertical separation to approach the theoretical max 3 dB of gain over a dipole antenna. Out of phase currents exist between and beneath the two current peaks, but are of small amplitude. * If you perform this check yourself, know the aluminum tubing has a non-conductive metal treatment coating. Place your probe on the fixing screws instead.