Introducing the Skyhawk:
A State-of-the-Art Trapless Tribander from Bencher/Butternut
The Skyhawk is a state-of-the-art tribander designed using the latest techniques in computer modeling and optimization. The antenna is essentially composed of three separate monoband antennas fed from a single feedline using an open-sleeve type feed. The antenna features three elements on both 20m and 15m as well as four elements on 10m; giving a total of ten elements on a 23 foot boom. The electrical design of the antenna is by Jim Breakall WA3FET and Nathan Miller NW3Z and the mechanical design is by Tim Duffy K3LR.
The open-sleeve feed allows a single element to be directly fed from a 1:1 Current Balun, eliminating troublesome and delicate gamma matching or other impedance matching techniques. In optimizing the driven element cell, special care was taken to keep the VSWR low across the entire 20m and 15m bands as well as the useful bottom portion of the 10m band.
While many antennas are optimized only at the band center (resulting in poor performance at the upper and lower band limits) the Skyhawk was optimized across each frequency band. The result is that the pattern of the antenna is excellent across each band as is reflected in the Front-to-Back numbers. One other important fact to note is that ALL of the performance information is given on the Skyhawk. Most manufactures tell you only what the PEAK performance of the antenna is and try to mislead you into believing that this is representative of the whole band. The numbers given at the end of this article are all calculated using the latest version of the Numerical Electromagnetics Code (NEC) and are a true representation of the antenna in free space.
The design team chosen by Bencher/Butternut for the Skyhawk is the major reason for the success of the antenna:
Jim Breakall is a Professor of Electrical Engineering at Penn State University and anyone who attends the Antenna Forum at the Dayton Hamvention will remember him for his many presentations over the years. He has also been an active researcher at the Arecibo Observatory and will spend 5 months there starting in January 1998. Jim and Nathan are currently building a contest station near Arecibo and will be active during the ARRL DX Phone contest using the call, WP3R.
Nathan Miller is a graduate student at Penn State and, among many other projects, has designed a series of contest-grade monobanders for use at both the Penn State contest station, K3CR, and at K3LRís multi-multi contest station. Also, keep an eye out for an article in the February or March 1998 issue of QST on a revolutionary 40m Yagi design Nathan optimized and built as a thesis project. If you are interested in building a competition grade monobander, feel free to email him at firstname.lastname@example.org
Tim Duffy certainly needs no introduction to active contesters. His consistently impressive multi-multi contest performance is a tribute to both his antenna farm and operators. His attention to detail is phenomenal and is reflected both in his station and in the design of the Skyhawk.
Keep an ear out for K3CR, K3LR and WP3R in the next DX contests!
True Free-Space Performance Characteristics for the Skyhawk
Effective boom length = 22' 0"
VSWR is better than 1.4 from 14.000 to 14.350 MHz
Front to back is better than 20 dB across entire band
F/B peaks at 14.150 MHz @21 dB
Gain is better than 7 dBi across band , free space
Gain is 7.15 at 14.000 and 7.4 at 14.350 MHz
Effective boom length = 15' 6"
VSWR is better than 1.5 from 21.000 to 21.450
Front to back is better than 16 dB across entire band
F/B peaks at 21.350 MHz at 24.5 dB
Gain is better than 7 dBi across band
Gain is 7 at 21.000 and 7.6 at 21.450 MHz
Effective boom length = 16' 9"
VSWR is better than 1.5 from 28.000 to 28.900
Front to back is better than 14 dB across band
F/B peaks at 28.500 MHz at 15 dB
Gain is better than 7.7 dBi across band
Gain is 7.7 at 28.0 and 9.3 at 29.0