The antenna is your first receiver, the second one, the so called “receiver” can only process what the antenna delivers. We regard the HB9CV antenna  (that you see above) as the most practical hand held antenna in field work in the 150 MHz region and therefore we use it as our standard antenna. This antenna type is also famous in the radio amateur scene but there you find it with a typical center frequency of 146 MHz . The antenna type has a bandwidth of 4 MHz and we deliver our antennas centered to the frequencies that you are using in your project, so if you are working around 150 MHz, you should not use a 146 MHz centered HB9CV avoiding gain loss. Here we touch another often found missunderstanding concerning antenna gain, expressed in either dBi or dBd. When you compare stated antenna gain datas, take a close look on the units in use, dBi refers to an isotropic radiator, dBd to a dipole, meaning that if the gain was expressed in dBi subtract 2.15 dB to get the dBd value and vice versa. Some clients ask for 3 element 150 MHz yagis whose dimensions fit into a square meter in the 150 MHz region, adding 1 - 1.5 dB more gain compared to the HB9CV, needing longer cables, remaining advantage - sportive arm training - caused by weight, so we recommend the use of our HB9CV as ”the field antenna” also availlable with flexible end rods (HB9CV flex). The "footprint" of the HB9CV is approx. 1m in width an only 25 cm in length.
You can order the single antenna , you can order it with grip and cable (BNC m / BNC m 1,3 mtr.) or it is already included if you order a DJ-X11 + HB9CV active antenna receiver unit.