DSFO222-16

The DS222-16 is a standard high performance K1FO yagi antenna design optimized for an optimum pattern and high gain across the 222-225 MHz amateur band. This antenna will provide great performance whether you are building an EME array, a tropo and meteor scatter system, or just want to add a new band to your arsenal! The DS222-16 is supplied with a T match feed and type N connector 50 ohm input with an integral n1/2 wave balun for maximum performance. The mast clamping arrangement utilizes a 3" x 5" extruded plate that is movable along the boom to provide maximum ease of installation on any mast size 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 on these pages below. Bandpass and VSWR curves will be here shortly.

DSFO222-16 YAGI ARRAY

To evaluate the bandwidth, click here. To look at return loss (VSWR), click here.

The DSFO222-16 specifications (and manual) are listed here.

The DSFO222-16 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! The feedpoint of the DSFO222-16 also faces in the opposite direction, as it is a center mounted design.

SAMPLE DRIVEN ELEMENT T MATCH DETAIL

The DSFO222-16 computer modeled patterns are here:

E&H plane patterns

Tune up directions and notes for our T matches are available here.