Broadband HF transmitting antennas described in this section cover continuously the range 14-30 MHz, some of them even 10-30 MHz. They feature reasonably low SWR in the whole range and have nice radiation patterns without unnecessary lobes or nulls. Because they do not use termination resistors nor lossy traps, their efficiency is very good.
Every symmetrical antenna covered in this section is compared with a half-wave dipole, and every vertical antenna - with a quarter-wave monopole or a quarter-wave GP. Because the broadband antennas have a little higher SWR than single band resonant antennas, they have greater losses in the coax that feeds them. To be fair, it has been assumed in the comparison that all antennas are fed via a 30-meter long RG58 cable. Additional loss due to higher SWR are subtracted from the broadband antennas gains, and such reduced gains are compared with the corresponding resonant antennas. Please note that in order for these comparisons to be valid, you must use an antenna tuner next to the transmitter. It can be a built-in tuner or an external tuner.
If you want to use a broadband antenna with a transmitter not having an antenna tuner, you'd better choose the antenna with as low SWR as possible. On the other hand, if you have an antenna tuner, your choice is less critical. In such case, mechanical simplicity or low wind load may be more important for you when choosing antenna version.
The majority of the presented here antennas were simulated in free space because the results of such simulations compare easier with other antenna designs. Please remember that if the ground is added in the computer model, the antenna gain may rise by up to 6 dB. For example a half-wave dipole has maximum gain of 2.15 dBi in free space, but it can rise over the ground even to 8 dBi depending on the installation height and selected ground properties. When comparing the antennas described here with the others, make sure they were simulated in identical conditions.
The monopole antennas requiring an RF connection to the ground were simulated with a system of radials placed slightly above the ground. I simulated the majority of the antenna presented here with NEC-2 based simulators, so I was unable to put the radials below the ground surface. If you have access to the NEC-4 or NEC-5 based simulators, you may want to repeat my simulations with the radials buried under the ground surface.
Please mind that the majority of my models are built with ideal lossless conductors of 2 mm diameter. Only some of them were simulated with copper conductors. Where it was so, this information is provided in the antenna description. If you would like to build a real antenna based on one of my models, I would recommend repeating the simulation with the conductors adjusted for the intended material, diameter and insulation if applicable. If computer simulation is possible for you, be ready to accept a little different SWR results than in the models. In my opinion, though, such discrepancies will be not very significant.
My article describing the broadband HF antennas appeared in the QEX 2020/03-04 and 2020/05-06. The majority of the designs presented here were covered in the article.