Correct. 1090 mhz isn't any aircraft band though. ADS-B are transponders mounted in an airplane to report positions to ground receivers for safety purposes mainly.Trying to understand this: so if your using the sdr with RTL 1090 program to listen to aircraft band then you need to use the little antenna for 1090 MHz because that's the frequency that RTL1090 operates on, but if your using your scanner like my PRO-668 to listen to the air band then you would want to use the dipole antenna for 127 mhz.
The calculator I used for the folded dipole is: Martin E. Meserve - K7MEM - Folded Dipole DesignI'm thinking about trying to build one of the 2 wire folded dipole antennas but I'm confused on the measurement for the materials. Lets say I wanted to build one for the aircraft band mid frequency 127 mhz. How long of a piece of copper-aluminum-brass rod/wire would I need? I found this formula:
L ft = 467/F mhz so 467 divided by 127 = 3.677 feet would that be right and then start bending it around to form the typical folded dipole shape. Or is there a lot more to it than that. The 1/8" brass rods I was able to find in the local hw store "Lowes" are only 3 feet long.
That is one thing that I like about using VRS. The polar plots are amazing at telling you how your antennas are working. In a few hours to a day you can learn a lot.I am definitely planning to build the 1/4 wave ground plane antennas that you suggested. I just have to get some parts in so I can start on it. The right connectors and copper wire, rods, tubing etc etc. One thing I do think a person sort of needs is a signal strength meter of some sort otherwise how do you really know if the antenna you built is in the right physical position, location, you need a way to tweak things and see the result on some sort of a meter. RTL1090 program has sort of a signal strength meter that helps when your trying to improve reception...well scanner have a signal strength meter of sorts I guess with the bar graph but it's pretty crude.