SteppIR manufactures freely tuneable multiband beams with 2, 3 or 4 elements for 40 to 6m or 20 to 6m. With the continous mechanical tuning of the element lengths SteppIR Yagis achieve the performance of comparable monoband beams - but on many bands. The similiar contructed λ/4 verticals offer always perfect match as tuned groundplane. The small packing size and the lightweight construction with glassfibre tubes makes these antennas an ideal companion for dx-peditions and fielddays.
The problem with traditional beams
Traditional multiband beams require traps, interlaced elements etc. to work on multiple bands. With these elements such an antenna is usually a compromise in respect to the possible maximum efficiency of an antenna. Monoband beams like the ZX Yagis would be an alternative, but who can put up three or more such beams?
The idea: variable lengths elements
FluidMotion, the manufacturer of SteppIR antennas has solved this problem in an elegant way. SteppIR vary the mechanical length of each element by means of a retractable metal band. This allows the antenna to be adjusted for any frequency (within the range) and work near the perfect optimum.
Contruction of a SteppIR
Each element of a SteppIR antenna consists of lightweight glassfibre tubes, the metallicc band run in these tubes. That means of course that the absolute size of the antennas does not change, the glasfibre tubes are not changed in length. The metallic bands are made of a special Copper Beryllium (CuBe) which withstands millions of movements. The excellent electrical contact is achieved with four self cleaning slider contacts for each element. The metal band itself is perforated, a sprocket wheel spools up the band. The sprocket is driven by a precision stepper motor, allowing for very precise positioning.
Each single element is controlled by a 4 wire cable, i.e. the 4-element SteppIR yagi requires 16 wires. Down in the shack a supplied controller is used to adjust the antenna. For the amateur bands various presets are available for each band. Further a "general" mode allows adjustment of the antenna to any frequency (within the specified range). Antenna setups can be stored for later recall, other functions allow the quick reversal of direction or the bi-directional mode where the gain is evenly distributed in two directions. An optional CAT interface for the controller allows direct control from most amateur rigs: the antenna is continously adjusted when the frequency on the rig is changed.
Optional 30/40m Radiator
This replaces the standard radiator and allows operation down to 40m. Available in two version: one as option when buying a new antenna and one as replacement part for an existing antenna.
Technical data and comparison table
SteppIR Dipoles and Yagis
The SteppIR Dipole and Yagis are available in five different versions, from one to 4 elements, covering different ranges. Each element is variable in length by using a motor driven metal band (Copper Beryllium). The metal band is protected by a glasfibre tube, the length of this tube does not change of course.
Like with all SteppIR antennas the glassfibre tubes have to assembled and isolated at first set up. This makes the SteppIR antennas very compact, that nice for shipment cost and expeditions.
Variable element length, but fixed element distance?
One of the most frequently asked questions is "Shouldn't the distance of the elements also change when changing element lengths?". To answer this question it is important to understand that Yagis can be designed to maximise different values. That can be max. gain, best Front/Back ratio, good bandwidth etc. But - these goals cannot be achieved all at once with the same design. Either you optimize a yagi for best gain, useful bandwidth and not so good F/B ratio. Or excellent F/B ratio at narrow bandwidth and mediocre gain etc. etc.
With a 3-element beam the optimum gain would be reached at a boom length of 0.4 λ. The best F/B ratio is achieved with a boom length of approx. 0.25 λ, but only at limited bandwidth. This results in 0.3 λ as a good compromise, with this it can be shown that a variable element length results in much greater effect than variable distance. Bandwidth is of no importance with a SteppIR antenna because the antenna can be adjusted to any operating frequency (within specified range). So a narrow bandwidth design can be selected which results in the best compromise solution at a given element distance. That is much more than what you can expect from a traditional monobander.
Gain and Front/Back ratio
Gain in dBD (Free space)
F/B ration in dB. The manufacturer denotes this value as "Front/Rear" and refers to the max. achieveable bakwards attennuation, whose maximum is not necessarily in the -180° direction.