Below are the questions asked during the live event, along with their respective answers.
A: The antenna tunes with the changing of element length to match frequency. It is optimized to the exact length required for each element throughout the entire range of frequencies in the mil-std. The lengths of the elements can not extend or retract past the listed frequency range. The antenna could be damaged as VSWR will increase rapidly. Other designs are possible to cover other frequencies.
Q: What is the maximum Power handling of the antenna?
A: 2500 watts Maximum at a maximum SWR of 3:1. Depending on the room, the required power output will usually be quite a bit less. This is not a system that needs to be blasted with power to get to the required specification. 2500 watts is usually more than enough.
Q: Can you make a larger antenna to go to lower frequencies?
A: Absolutely. The only limitation to going lower in frequency would be the space constraints of the chamber. We commercially manufacture antennas that have a frequency range of 3-200 MHz, so the technology is easily adapted for lower frequencies. We are also looking at novel ways to keep the size profile reasonably small while still reaching the lower frequencies and we welcome developmental partnerships.
Q: How much will one of these systems cost?
A: There are a number of pricing configurations and options. Please contact your manufacturers representative for our products for more information. A list of reps can be found on our website: https://steppir.com/contact/.
Q: Is this antenna allowed by MIL-STD-461?
A: Yes, it is a linearly polarized Yagi antenna, with 2 elements active on 30-55 MHz and 3 elements from 55-200 MHz. The advantage our antenna employs over a bicon, log periodic or even another fixed-length Yagi, is that we dynamically tune each element to the exact length required so that the antenna is resonant at each individual frequency.
Q: If the antenna position is varied does the tuning need to be re-accomplished?
A: As long as the antenna is placed in the same position as before, it will function well without retuning. We suggest you mark the floor with blue tape so repositioning will be accurate. The system is surprisingly repeatable when following these simple guidelines.
Q: How long does a tuning process take and is this done with or without a test sample in the chamber?
A: The tuning process takes between 4-8 hours for each position (Horiz.-Vert.) and is repeatable when placed in the same position in a particular room.
Q: Which MIL-STD-461 test or tests benefit from this antenna? Can the antenna be used for other MIL tests such as MIL-STD-464?
A: RS103 for MIL-STD-541 in the range of 30MHz to 200MHz. The antenna can be used for MIL-STD-464 so long the max input power is not exceeded.
Q: Does the tuning need to be accomplished with the EUT installed?
A: No, the EUT has not shown to have a significant effect on the tuning. However this is not a finite statement – I’m sure there are some EUT setups that may have some kind of an effect, especially large ones. What we have seen so far has been negligible effects.
Q: Does SteppIR offer an installation and configuration service? Can users do it themselves?
A: We absolutely do offer installation and training services, and we recommend you take advantage of it. After a day or so of training and orientation, the customer usually will have no problems operating the system themselves.
Q: How much ceiling height does the antenna require?
A: The dimensions for the antenna are 110″ wide in the horizontal position and 39″ deep. In the Vertical position, the height is 110″ but you need to get the antenna off of the ground – we recommend 17″ above ground, so you need 127″ give or take to operate in the vertical position. For height-challenged rooms, we offer winglets that look a lot like what you would see on the wing of an airplane, that allow us to trim another 10″ off of that height requirement.
Q: Can the antenna be used in an open area?
A: If by open area you mean outdoors, absolutely. In fact, when you get outdoors, we have much more flexibility on the size of the antenna and can cover lower frequencies and create more powerful antennas. If by open area you mean a larger chamber, we can do that as well.
Q: How was it determined that the E Field is at the fundamental frequency vs at harmonics?
A: During development, a 2nd antenna was inserted into the room for measuring strictly harmonics. For tuning, a spectrum analyzer is used to read only the fundament frequency. Since the SteppIR antenna is resonant and is not using any tricks such as traps & interlacing, the SteppIR antenna acts as a harmonic filter. There is nothing fancy there, resonant antennas filter harmonics, and ours is resonant everywhere within its range. The SteppIR system will filter out harmonics by 25 dB typical and usually much more – it is unlikely the antenna will contribute to the field measurement when a broad-band field probe is used during testing.
Q: In an open field, how stable is the antenna to high winds? How would you safely stabilize it?
A: Our outdoor commercial antennas are made to handle 24/7/365 harsh weather conditions, and the concept is applied to the SY3-EMC system as well. We would need to make the element housings more adaptable to outdoor environments if you were going to keep the antenna permanently outdoors, but we have done this thousands of times over the last 20 years of manufacturing antennas specifically for outdoor use. Short answer – not an issue at all. In high winds, more attention would need to be paid to the antenna stand/mast/tower. The antenna itself would be fine.