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UPDATE May 2012: I had a drive shaft failure - my
antenna had the "gray plastic" drive shaft and I was almost waiting for this.
This version of the drive shaft is known for an increased incidence of failures. |
SteppIR claims that they have fixed the problem now with an "updated design" shaft. Hopefully they did - it was about time! I've been reading about these failures for years until finally I experienced it for myself and honestly I am not happy about the way they handle the issue! Changing the design is a sign of acknowledgment of design issues (not to mention the amount of reports all over Internet, from users who had this type of failure), yet they expect the customer to pay for it.
More information regarding the broken shaft and pictures from the repair - http://blog.kotarak.net/2012/05/steppir-bigir-broken-element-drive.html
Well... If we put aside the fancy tuning feature, the BigIR is a classic 1/4 wavelength vertical (and it can be 3/4 wavelength on some bands). There are many discussions in different books and articles regarding the performance of the vertical antennas so I am not going to start a new one. BigIR is no different from any of those classic vertical antennas when we are looking at it on a fixed frequency. As with other verticals, it picks up more noise than a dipole or Yagi, it is omni-directional, it has low take-off angle, the gain is not spectacular, etc.
One important thing to remember about 1/4 wavelength verticals as BigIR is that the actual vertical is just half of the antenna system. The other half is the radial plane that takes care of the losses in the ground (at least in the near field).
If one wants an efficient, well performing antenna, no corners should be cut when installing the radials - for ground level mounted antenna with buried radials: more radials - the better, the longer they are - the better. I decided to use only 60 radials, because the increase in efficiency between 60 and 120 is not that significant! My radial system is employing radials with different lengths (the maximum possible as the space in my backyard permitted) with the shortest ones around 32 feet and the longest over 70 feet (1/2 wavelength on 40 meters). Major factor in the performance of the antenna is the quality of the ground - I think that I have a very good soil (antenna-wise) with no sand, no rocks and high water table but there is not much I can do about the soil anyway! My house is on the top of a hill with steep fall-offs so this is also good. One thing I have control over though is the radial plane and I made sure that it is done properly. Another factor is the location of the antenna - I installed mine as far away from the house as possible (~80 feet) and I do not have any structures around the antenna that might affect the radiation pattern. That is the theory at least! The practice turned out to be not that far away from the theory. The antenna performed excellent! I was able to work many DX station with only a few radials in place. The radials are on-going project and I hope to have all of the 60 planned radials installed soon!
Now, what makes SteppIR antennas and in my case the BigIR so unique? A feature that I like to call TOF – Trim On the Fly. This feature is why the BigIR is such an attractive antenna – it gives you the ability to trim the length to almost infinite number of resonant verticals! The tuning step using the buttons of the controller is 50 kHz and by using PC software the antenna can be tuned every 25 kHz. Very nice feature is the ability to connect the controller to the radio and track the frequency, the transceiver is on.
The SWR was too low, but after I removed the antenna tuner that I had in-line (the tuner was in BYPASS mode anyway) the SWR went up to 1.3:1 and the feedpoint impedance measured 36.7 Ohm which is consistent with 1/4 wavelength vertical.
The overall mechanical construction looks solid and well done. I think the EHU could have been designed a little better. I will see what the future holds for the EHU and the copper-beryllium tape in particular as far as wear-and-tear is concerned. I was hopping for more intelligent way for the controller to know when the element is fully retracted – like opto-coupler detecting a perforation on the tape when the element is fully retracted or even counting the perforation to measure the exact length of the element. On other hand this sort of feedback will complicate the things and would make the antenna even more expensive.
The antenna requires almost no maintenance – maybe from time to time replacement of electrical and silicone tape or a rubber boot as the Nature's elements leave their mark. I sprayed the whole antenna with UV protective coating so this should also help.
A great thing is that during strong winds or lightning storm the antenna element can be retracted in the housing. In such case the wind damage will be inexpensive to repair should any of the fiberglass tubes breaks. This feature also could potentially save the equipment from a lightning hit once the antenna is retracted as there is no expensive high-conductive rod sticking 35 feet in the air.
Overall, I am happy with my antenna and I hope to use it for a long time!
As nothing is perfect here are few gripes that I have:
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