Doesn’t having the element spacing fixed significantly compromise the antenna?
First of all, there really is no “ideal” boom length for a yagi. To get maximum gain the boom of a 3 element beam should be right around .4 wavelengths long. This would allow a free space gain of 9.7 dBi, however the front to back ratio is compromised to around 20 dB. If the boom is made shorter, say .25 wavelengths, the front to back can be as high as 35 dB, but now the maximum gain is about 8.6 dBi. Shorter booms also limit the bandwidth, which is why right around .3 wavelengths is considered the best compromise for gain, front to back and bandwidth. It turns out that being able to tune the elements far outweighs being able to choose boom length. We chose 16 feet for our boom length which equates to .23 wavelength on 20 meters and .46 wavelength on 10 meters, because very good yagi’s can be made in that range of boom length if you can adjust the element lengths. When bandwidth is of no concern to you (as it is with our antenna), you can construct a yagi that is the very best compromise on that band and then track that performance over the entire band. It is this ability to move the performance peak that makes the SteppIR actually outperform a monobander over an entire band – even when the boom length isn’t what is classically considered “ideal”. Bear in mind that a yagi rarely has maximum gain and maximum front to back at the same time, so it is always a compromise between gain and front to back. With an adjustable antenna you can choose which parameter is important to you in a given situation. For example, you might want to have a pile-up buster saved in memory, that gets you that extra .5 – 1.0 dB of gain at the expense of front to back and SWR – when you are going after that rare DX!
How is RF power transferred with the SteppIR antenna?
The RF power is transferred by brushes that have 4 contact points on each element that results in a very low impedance connection that is kept clean by the inherent wiping action. The brush contact is .08 in thick and should last thousands of cycles. The power rating of 3000 watts is continuous on CW or SSB, but as far as “key down” duty we have only tested it to 5 min. The copper beryllium tape is .545 inches wide and presents a very low RF impedance that results in conductor losses of -.17 dB with a yagi tuned to have a radiation resistance of 15 ohms, which is about as low as most practical Yagis run. The type of balun we are using can handle tremendous amounts of power for their size because there is almost no flux in the core and they are 99% efficient. That coupled with the fact that our antenna is always at a very low VSWR means the balun will handle much more than the 1500 watt rating, how much more we don’t know. Jerry Sevicks book “Transmission Transformers” (available from ARRL) has a chapter (Chap. 11) that discusses the power handling ability of ferrite core transformers.
What is the 180° mode and bi-directional mode?
The 180° mode allows you to “rotate” the antenna 180 degrees in about 3 seconds – Simply push a button and the reflector and director switch with each other, so you only have to rotate the antenna with the rotator 180 degrees to cover the world.The bi-directional mode allows you to operate the antenna with gain in opposite directions, simultaneously!
What kind of gain and front to back ratios can I expect from my 3 element SteppIR yagi?
We did extensive testing at our Moses Lake, WA range, and the SteppIR yagi performed as theory predicted. According to EZ-NEC’s and YO -PRO’s antenna analysis, the practical antenna gains possible with a boom 16′ long, range from 8.2 dBi to 9.0 dBi. We are very close to those figures from what we measured on our antenna range. Front to rear performance is an outstanding aspect of this antenna. The SteppIR 3 element yagi has rated front to rear ratios of 20 – 35 dB on 20, 17 and 15 meters, and 10 – 20 dB on 12 and 10 meters. Front to rear is the response from the back of the antenna at it’s least favorable point. Front to back, on the other hand, is simply the response of the antenna at exactly 180 degrees. In many cases this is not the worst case response from the back of the antenna. We feel that specifying front to rear measurement is much more useful to our customers. Also, keep in mind that front to back varies with the angle of arrival of the particular offending signal. In some cases, you may find front to back exceeding 20 – 35 dB, but it will never be less than that.
How resistant to corrosion is the conductive strip?
The conductive strip is special blend of copper beryllium, specially manufactured to our specifications. This type of copper beryllium has been used for continuous exposure undersea saltwater applications, where product life exceeded 30 years. We have soaked it in brine for 60 days alternating with air exposure and then checked the connection resistance and found that with one pass under the brushes or 6 volt applied, a very low impedance connection was observed. The tape is designed for upwards of 1 million cycles, as long as it does not exceed its stress point, which we were very careful to ensure in our design.
What is the Transceiver Interface?
The transceiver interface allows the SteppIR antenna to communicate with your rigs Computer output port. When this function is selected, the antenna will automatically adjust its length as you tune through the bands. This feature is available on all the SteppIR antennas as an option.
How well will the antenna handle extreme weather conditions (wind, heat, ice)?
The SteppIR antenna is rated from -20 deg F to 130 degrees F. The antenna is made entirely of corrosion resistant products (stainless steel, aluminum, fiberglass and thermoplastics). The conductive elements are protected by the fiberglass support tube, and the entire unit is sealed & vented. The SteppIR is wind rated to 100 mph / 160.9 kph. We have designed the SteppIR to work trouble free in all weather conditions within the parameters of it’s environmental specifications. There are thousands of SteppIR antennas world-wide, with many being routinely exposed to extreme weather conditions.
Is the SteppIR dipole, 2 or 3 element yagi upgradeable?
The element expansion kits allow you to convert our dipole, 2 and 3 element yagi to a 2,3 or 4 element, depending on your situation. Each kit consists of one, two or three elements and the appropriate boom sections and hardware required for the conversion. Antenna control cable is available for purchase, but is not included in the element expansion kit. The DB series antennas are not upgradeable.
Is the SteppIR antenna available as a vertical?
We have a 18 foot and a 32 foot vertical that operate as a classical 1/4 wave of 3/4 wave antenna or you can use our Dipole as a 1/2 wave “vertical dipole”. You can get very good performance in this manner.
Could you explain the matching system for the yagi?
The matching system is a very broadband transmission line transformer designed by W2FMI. This balun includes a 22 to 50 ohm UNUN as well, to match Yagis that are in the 20 to 25 ohm impedance range with a very low VSWR. We chose 22 ohms because that is the impedance of practical yagi’s that exhibit very good gain and front to back ratios. Since we control each element very precisely we make Yagis that are 22 ohms. If you want more gain, you could change the lengths (in the create antenna mode) and get a lower impedance antenna, if you could live with a little higher VSWR.
Does the entire antenna adjust, or do the poles stay out once extended?
The fiberglass element supports are 5’ (1.5 m) long when collapsed. The fiberglass supports are 18’ (5.5 m) in length when fully extended. Each element is made up of two of the fiberglass element supports, for a total element length of 36’ (11 m). The fiberglass element supports remain extended at all times. The conductive copper beryllium strip is on the inside of these supports, and is adjusted to the required length by the Steppir controller.
Why should I buy an new SDA-100? What are the advantages?
There are a number of optional features that are available that were not available on the Original Controller including: Tuning relay option: This prevents keying an amplifier when the elmenets are moving; Advanced Lightning Protection board: This greatly reduces the chance of having damage to the controller from a nearby lightning strike; Easy to upgrade software: As new upgrades to the firmware are released these can be uploaded to the controller from a local computer rather then having to obtain a new chip; New operating features: one button retracting of elements and automatic shut-down, as well as the ability to step the frequency in either 100 kHz or 10 khz steps.
Q: How many and how long should the radials be on my BigIR Vertical?
As many and as long as you are able to install. Seriously, the more the better–up to a point.If you are planing a vertical it is recommended you read and study the work done by Rudy Severns, N6LF, on his website http://www.antennasbyn6lf.com/ Rudy has done extensive study on radial systems and has a lot of very good information. The “General Rule” is to have as much copper in the ground as possible close in to the antenna–within about 2/3 of a quarter wavelength at the lowest operating frequency. If you plan to use elevated radials you will need at least 2 tuned radials for each band.
Can I mount the vertical on a post, say 6 to 8 feet above the ground, and put the radials on the ground under it and just connect the antenna ground to the radials with a long wire running down the post?
No. The wire connecting the antenna and the radials then becomes a part of the antenna and will greatly effect the tuning of the antenna as well as effectly moving the feed point up the antenna and making it very difficult, if not impossible, to acheive a good match.