The DS222-10RS is a new high performance K1FO yagi antenna design optimized for the best "Rover footprint" or size. The idea was to design a yagi that delivered great performance across the 222-225 MHz band, but with a compact footprint that was "street legal" when assembled and driving down the nation's highways. A 96" boom length will satisfy highway width requirements even with the yagi nested sideways on the vehicle. The DS222-10RS is supplied with a T match feed and type N connector 50 ohm input. The mast clamping arrangement utilizes a 3" x 5" extruded plate and is movable along the boom to provide maximum ease of installation on any vehicle. Mast size may be up to 2' diameter. This design has been carefully checked out in the real world to ensure peak performance.. This antenna provides maximum gain at about 223.1 MHz, and will provide great performance all the way up to 225 MHz. A higher frequency peak is needed for good wet weather performance on higher frequency yagis, and our choice has netted a design that is remarkably stable in wet or dry weather. Forward gain, wide bandwidth, and exceptionally clean patterns are the most notable characteristics of this antenna, as with all of the K1FO style designs. The net result is wide beamwidth, and a clean lobe structure coupled with a very high gain figure. Clean H-plane patterns translate to efficient stacking with maximum possible gain and manageable array sidelobes, should you wish to stack these antennas in a larger array.
All Directive Systems antennas are verified for proper performance on an antenna range with state of the art swept measurement equipment to record the results. Some performance curves have been provided below on these pages below.
The DSFO222-10RS specifications (and manual) are listed here.
The DSFO222-10RS yagi employs a traditional modified T match and half wave balun to match your 50 ohm feedline to the driven element. The T match and half wave balun provides a great method for achieving proper match along with exemplary decoupling of the feedline from unwanted antenna currents. At these higher frequencies, gamma matches and other matching methods used on lower frequencies, start to behave erratically. They tend to unbalance the feedpoint and cannot provide an effective rf ground as a result. The result is poor decoupling of the feedline and the antenna boom itself! Poor decoupling effects can reduce forward gain by large amounts. If any power flows on the outside of the coaxial cable, or along the antenna boom, gain or efficiency suffers drastically. Poor decoupling will show up as varying VSWR as the feedline is handled. Deep response nulls within the passband of the yagi are a tip off as well. Any skewing of the main lobe off the boresite heading indicates out of control rf currents caused by poor (or no) decoupling.
A sample close up of a typical Directive Systems "T" match is shown here. The actual antenna shown is a 432 yagi and it presents a more compact photo which shows maximum detail. The 222 MHz T match looks similar, just a bit bigger!
SAMPLE DRIVEN ELEMENT T MATCH DETAIL
The DSFO222-10RS computer modeled patterns are here: