In general, the vertical dipoles that look like the letter, "I" are center-feed vertical dipoles with top and bottom "T-bars" for end loading. The "I" style design was developed via Team Vertical many years ago as a replacement for the more complex "ZR" style. It was produced in many models beginning in 2001 from single band 80 through 6 meter antennas to remote switched, multi-band 20-17-15-12-10 and 40-30-20. It was produced by my company, Force 12, Inc., and called the "Sigma" series. Team Vertical can attest to the design effectiveness, having set several CQWW CW World Records using them. The "I" style vertical dipole is an excellent electrical performer and came out of a decade of research and development beginning with the "ZR" vertical dipole in the late 1990's, the V-3 and then the "SVDA" series. Although the "I" style vertical dipole continues to be a top-notch antenna when designed and installed properly, it has mechanical and visual short-comings. One of these mechanical issues on the "I" style vertical dipole is having the feed point at the center of the antenna. This requires the coaxial feed line to be run away at an angle, usually about 45° for several feet. On the remotely switched ones, the control cable must also be run in the same manner and in many installations, this is not a simple task. If this is not done, the feed line and / or control cable become involved with the antenna. The upper "T" bar presents a mechanical situation making the larger antennas difficult to erect at times (top heavy) and sensitive to the wind rotating the antenna. The smaller ones need to have a more substantial (larger) vertical section to support the "T" bar, plus the bar is easily a visual drawback. Enter the Bravo series which is also lower cost. See diagrams in download section below. Producing a product when cost is not an issue is quite simple - just keep adding more parts and processes! The Bravo series takes a different road, not often traveled. Right from the start, each component is verified that it needs to be there. It is also verified that it is the lowest cost, without compromising performance. Another design goal was to make the Bravo series as field repairable as possible, especially when out of reach of mail service, such as DXpeditions.
Some items of obvious added cost that are not in the Bravo series are:
1) powder-coated components - powder coating is an insulator (not required) and impossible to repair in the field. 2) sliding joints with friction connections - these should be solid, good electrical joints, especially for DXpeditions. 3) black color for the antenna - absorbs maximum heat and is not visually neutral.
Under the Reference tab of this website you will find 3 Bravo manuals.