| Sommer XP70 Series Beam Antennas
The XP70 series beams are designed for the amateur with all-out performance in mind. Although the boom length is only 20 feet, XP 70s have easily outpaced much larger, conventional antennas in careful testing. The key is the total elimination of traps, which rob performance from even the largest of multiband antennas. Because of their high efficiency, XP70 series antennas suitably replace 4- and 5-element antennas of conventional design.
For the 15 m (and 17 m) bands, four directly fed 5/8-wave elements in conjunction with elements 1B and 4A form a typical band gain of 9 dB/D. Operation on 17 meters requires an optional 8.2 (26 ft) element at boom location Z which does not influence the 10-20 settings but has the same properties on 15 meters.
All elements are working on the 10 and 12 meter bands and contribute to a 9.5 dB/D gain.
Coaxial stub housed in a plastic bax enables operation on the 30 m band without any mechanical extension. Using this configuration, the typical gain is about 2 dB/D.
The 40 m band is activated by use of an individual power coil mounted at Y, which yields a 0 to 2 dB/D gain on this band.
Remember, a 3-element monoband beam has 4 to 6 dB/D (see ARRL Antenna Book).
* Gain determined in the main lobe as described in the ARRL Antenna Book, 14th ed. pg. 15-23. Measurement accuracy according to CCIR plus/minus 2dB.
** F/B ratio and SWR vary according to conditions--e.g., electrical height above ground.
*** Plus or minus 10%
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