In this thread, I would like to discuss pros and cons of various multiband rotary antennas for the 10 m through 20 m bands. But I would like to discuss facts and figures rather than opinions. So, I will try to model the antennas that you think should be included. One reason of starting this topic is my own need for such an antenna. I am not in a hurry but I would like to build such an antenna in the near future. Moreover, I am doing a small favor to W7CJD who expressed interest in this sort of discussion in the other thread in this forum. So, one reader and active debater is practically guaranteed. Let's start. Fan Dipole This is the simplest 5-band antenna that comes to my mind. A picture below shows how you can construct a rotary version of a classical fan dipole. You just need two fishing poles and some spreaders. I copied the photo from http://www.g8njj.org.uk/index.php/antennas/96-the-batwing-fan-dipole The first question I had to answer when modeling was: how close to one another the dipoles should be. The closest separation I could found on the Internet was 4 centimeters see the picture below. I have found this picture onhttp://www.angelfire.com/mb/amandx/dipole.html. My first model looked like that: Such antenna with radiator lengths optimized for the centers of bands had very high SWR at 21.0, 28.0 and 29.0 MHz (7, 497 and 6 respectively) Please note that during all simulations, each time I was optimizing length of the radiators for the best combination of gain and SWR at the following frequencies: 14.175, 18.118, 21.225, 24.94 and 28.5 MHz. I wanted to cover whole bands except for the 10 m band where I regarded 28.0-29.0 MHz coverage as sufficient. Back to the antenna. I increased the separation 2.5 times to 10 cm and the 15 m band was now fully covered but SWR at 28.0 MHz, though somewhat reduced, was still much too high (>240). When I analyzed radiator currents at this frequency, it became obvious that the proximity of the 10 m and 12 m band radiators created the problem. See the picture below. Perhaps that’s why the fan dipole presented in the picture above lacks the12 m band. Increasing vertical separation between those two radiators to 20 cm helped only marginally. So, I decided to shift the 10 m band radiator from the bottom to the top - above the 20 m band radiator. Improvement was significant but still the SWR at 28 MHz was too high. I re-arranged the order of all radiators to reduce interactions. The new order was: 10m, 15m, 20m, 17m, 12m. I placed the feed point in the central radiator (20 m band). Thanks to that change, bending of the radiators near the feed point was as low as possible. I gradually increased the separations between the radiators to: 25 cm, 30 cm and 35 cm. 30 cm (or 1 foot) proved to be enough separation to ensure the bandwidth I wanted to achieve. The final model has 30 cm vertical separations between the radiators and looks like that: The dimensions are: d=0.3, a14=5.121, a18=4.028, a21=3.446, a25=2.802, a28=2.451meters Overall length: 11.242 m, height: 1.2 m, turn radius: 5.621 m. Required balun: 1:1. Find below the simulation results. SWR - free space SWR - real average ground, h=8 m Note that the minimum of SWR does not agree with the optimization frequency because my settings of the 4nec2 optimizer were: 50% for SWR minmalization and 50% for gain maximization. Evidently, SWR minimum does not agree with antenna gain maximum. So, for example, when trimming 10 m band you should aim at getting SWR minimum not at 28.5 MHz but at 28.15 MHz as you can clearly see in the graphs above. Radiation patterns of the fan dipole are practically the same as those of half wave dipoles and I will not present them. In the table below, I gathered calculations showing how the fan dipole compares to a half wave dipole in free space. I compared not only the antenna itself but also the system: an antenna with a transmission line (A+TL). That's because the antennas under comparison differ in SWR values so the losses in a real transmission line will be different. I assumed 30 meters (ca. 100 ft.) of RG58 cable and used AC6LA's TLDetails program to calculate the SWR as seen by a transmitter “SWR (A+TL)”, and the total loss in the RG58 cable “TL Loss”. The final result is in the rightmost column. The fan dipole with 30 meters of RG58 when compared to a HW dipole with the same transmission line is worse by 0.04-0.74 dB. I think we can totally neglect such small difference and consider the fan dipole as equal to the HW dipole. To summarize: - ensure at least 30 cm (1 foot) separation between radiators - ensure maximum physical separation between 10 m and 12 radiators - to win extra split decibel, rearrange the order of radiators to: 10m, 15m, 20m, 17m, 12m and place the feed point in the 20 m band radiator center. That's it. The NEC2 models are attached of the dipoles and the fan dipole in two versions: free space and with real average ground. The next antenna I want to analyze is a broadband fan dipole for the 14-30 MHz range. I designed it some time ago. I think you will be interested in comparing it with a classical fan dipole. But I need a few days to prepare the materials. What should be the third rotary multiband antenna to be compared?