Skip to content

About SteppIR

SteppIR History

Fluidmotion Inc. dba SteppIR Antennas was founded in May of 2001 by Mike Mertel K7IR, Jim Thomas K7IRF and John Mertel, WA7IR.

The company was founded with the intention of manufacturing a pump for the chemical process industry.  The company name of Fluidmotion was an obvious reference to the movement of fluids.

While working on the pump development, the company was also spending time to advance an idea Mike Mertel had begun to develop – a Yagi antenna that would work on the Amateur Radio WARC bands.   Early attempts led to many failures, and the project remained more of a hobby than a business venture.

The trio gave up on the antenna project several times, but eventually finalized the basic design that is used to this day with all SteppIR antennas.

In May of 2001, the pump project, now called the “Hammerhead”, was being successfully beta-tested at Honeywell Engineering.  At this same time, Fluidmotion had created a working version of the antenna design and cycle testing had begun to determine mean time between failure (MTBF) data.

The company had reached a crossroads of sorts – keep developing the pump as originally planned, or introduce the finished antenna product to the marketplace.  The decision was made to determine market viability by participating in the 2001 Hamvention trade show in Dayton Ohio – the largest convention of its kind in the world.

The antenna garnered a significant amount of attention at Hamvention, resulting in thirteen antennas being purchased, all of them 3 element Yagi arrays.  The show’s success made the decision an easy one, and Fluidmotion (the antenna company) officially began!  There was considerable confusion surrounding the name Fluidmotion – potential customers assumed the name implied that there was fluid inside the antenna.  Because of this confusion, a dba was created in the name of SteppIR Antennas.

Of the thirteen antennas originally ordered, the first one shipped was to Kim Bottles, K7IM.  In order of purchase following K7IM are:  Robert Fuller W7KWS, Jeff Battin KO7P, David Brandenberg K5RQ, Ralph Braun N8GNP, Randy Hofmeyer N8DAN, Jim Linton AB9CN, Brad Noblet WA8DWG, Joseph Roventini WA2RYY, Gene Tonn K4COH, Ron Serfield NA6RS, Richard Feldman K8HGY and Rudy Severns N6LF.  The company greatly appreciates these “early innovators” courage in purchasing a product that at the time, was considered a novelty.

Since that first year, thousands of SteppIR antenna products have been sold world-wide and the product line has grown to include many different types of antennas.  We are thankful to each and every one of our customers – we believe that SteppIR owners are the best and most loyal customers on earth… a biased opinion to be sure, but in our opinion… a valid one nonetheless!


SteppIR -  Why Compromise?

The SteppIR antenna was conceived to solve the problem of covering the eight ham bands (40m, 30m, 20m, 17m, 15m, 12m, 10m and 6m) on one tower without the performance sacrifices caused by interaction between all of the required antennas.

Antenna’s are available that cover 40 meters through 10 meters by using interlaced elements or traps, but do so at the expense of significant performance reduction in gain and front to back ratios. With the addition of the WARC bands on 30m, 17m and 12m, the use of interlaced elements and traps has clearly been an exercise in diminishing returns.

Obviously, an antenna that is precisely adjustable in length while in the air would solve the frequency problem, and in addition would have vastly improved performance over existing fixed length antenna’s. The ability to tune the antenna to a specific frequency, without regard for bandwidth, results in excellent gain and front to back at every frequency.

The SteppIR design was made possible by the convergence of determination and high tech materials. The availability of new lightweight glass fiber composites, Teflon blended thermoplastics, high conductivity copper-beryllium and extremely reliable stepper motors has allowed the SteppIR to be a commercially feasible product for over 10 years.

The current and future SteppIR products should produce the most potent single tower antenna systems ever seen in Amateur Radio!  We thank you for using our SteppIR antenna for your ham radio endeavors.

Warm Regards – Mike Mertel K7IR

Mike K7IR


SteppIR  Design

Currently, most multi-band antennas use traps, log cells or interlaced elements as a means to cover several frequency bands.  All of these methods have one thing in common–they significantly compromise performance.  The   SteppIR  antenna system is our answer to the problem.  Resonant antennas must be made a specific length to operate optimally on a given frequency.

So, instead of trying to “trick” the antenna into thinking it is a different length, or simply adding more elements that may destructively interact, why not just change the antenna length?  Optimal performance is then possible on all  frequencies with a lightweight, compact antenna.  Also, since the  SteppIR can control the element lengths, a long boom is not needed to achieve near optimum gain and front to back ratios on every frequency between 40 meters and 10 meters.

Each antenna element consists of two spools of flat copper-beryllium tape conductor mounted in the element housing unit.  The copper-beryllium tape is perforated to allow a stepper motor to drive them simultaneously with sprockets.  Stepper motors are well known for their ability to index very accurately, thus giving very precise control of each element length.  In addition, the motors are brush less and provide extremely long  service life.

Copper tape drwg

The copper-beryllium tape is driven out into a hollow fiberglass elements support tube (see below),  forming an element of any desired length up to the limit of each specific antenna model (a vertical uses only one side).  The fiberglass elements support tubes (poles) are telescoping, lightweight and very durable.  When fully collapsed, each one measures approximately 59” in length.  Depending on the model, there may be additional extensions added to increase the overall element length.

The ability to completely retract the copper-beryllium antenna elements, coupled with the collapsible fiberglass poles makes the entire system easy to disassemble and transport.

The antenna is connected to a microprocessor-based controller (via 22 gauge conductor cable) that offers numerous functions including dedicated buttons for each ham band, continuous   frequency selection from 40m to 6m (depending on the model).  There are also 17 ham and 6 non-ham band memories and you can select a 180° direction reversal* or  bi-directional* mode and it will adjust in just about 3 seconds (* Yagi only).

Principal of design

Theory of Operation

The SteppIR antennas length are controlled by a microprocessor that has lookup tables that contain a computer modeled antennas that has also been range tested for optimum performance. The microprocessor looks up the length in the table for each element and converts it into motor “steps”. It takes 200 steps to make the motor do one revolution, so you can see that the motors and thus the element length can be controlled to a high degree. The microprocessor sends the motor step information to an integrated circuit motor controller, one for each element. This allows all the elements to change length simultaneously at a rate of 1.33 feet per second thus speeding up frequency changes.

The antennas were modeled every 250 KHz throughout the antenna frequency range and in between those points the microprocessor extrapolates new values until the next 250 KHz segment is reached. It was found this is more than adequate spacing to insure that the changing electrical boom length is insignificant.  When the 180 deg mode is selected an entirely new antenna model is used because the element spacing is now different.  The four element uses two reflectors in the 180 deg mode to create a better antenna than was possible just using three elements in this mode.

In the bi-directional mode we create two directors on either side of the driven element. This results in a beam with gain out both ends. The desired antenna impedance is a little harder too keep at the desired 22 ohms so you may find VSWRs are sometimes  higher in bi-directional mode (in some cases as high as 1.5 – 1.8:1).

Our antennas operate much like hard disk drives do, they both are open loop systems. What this means is instead of trying to design a sensing system to tell you where the read head or element is (which is very difficult in both cases) you simply start at a home position and use a stepper motor or servo that by its nature has perfect positional accuracy. The only thing that will get the stepper motor and microprocessor out of sync is unexpected power loss or a mechanical blockage or failure. The calibrate mode will fix any out of sync condition by assuming it has no idea how much copper element is extended and then retracting long enough to insure the full length of copper beryllium tape that is in each element is brought to the home position. If less than the full length was extended the motor simply stalls (at half power) until the cycle is complete. The microprocessor then knows all elements are “home” and proceeds to extend the elements to the frequency the controller was set to when the calibrate cycle was initiated.

When the motor is miss-stepping due to being physically stopped (such as during a calibrate) it makes a rough growling sound as opposed to a smooth whirring during normal operation.  Stepper motors must be ramped up rather slowly to ensure they don’t miss steps and get out of sequence with the microprocessor. This is the reason you will hear a definite clicking at the start and end of a motor running. This is normal. The sound made by the stepper motor can be very useful in troubleshooting problems so try and pay attention to the different sounds and learn to identify normal operation and stalling.