They are center-fed Dipoles. Some are just wire like those others are molded T-shaped.
868, 900, 915 ā¦ Slight technical differences, but ā¦ yeah, same same. More important, same antenna.
I had to check what I did for this one. Looks like the kiss-method. Cut-off end of a tye-strap for support, and some heat shrink. Then used another tye-strap to hold it down.
Dave, thanks for the reply. Back in my shortwave listening days I put some effort into understanding antennas. The best antennas for the 30-50 Meter bands were dipoles. The engineering said use a 50 Ohm coax to a Balun in the center tap. 75 Ohm could be utilized if cost was a factor. The Balun and coax would shield the lead wire from resonating with the antenna and upset the antennaās tuning.
The Radiomaster antenna appear to be made from an unspecified coax. I did the math on the Dipole and Elementās length and it appears to be tuned to the 868/900MHz side. The Dipole and element lengths matched my calculations. This puts it slightly out of tune for the required 915MHz band. To settle this to my satisfaction I might pop for a NanoVNA analyzer.
On the TX side Radiomaster NOMAD uses the same antennas for 2.4GHz and 915MHz. I donāt understand that either. For now Iām going to just use the Radiomaster antennas that come with the set. Everyone says it is the more reliable R/C system available today. I believe it.
Allister, thank you very much for the image of your drone. Your mounting scheme is what I was imagining. Looks like you have the ability to make 3D printed parts. Iām envious. I do have a block of nylon, a small band saw and a desktop mini mill. We will see what happens.
My current thinking is to get the antenna element as far above the droneās top deck as possible. I still need to think through the antenna placement. The project is still a little way from assembly.
Everything I have learned about this radio system points to the long range capability. I want to leverage this with this build. I live in Washington State USA. About 1/3 of the state area is National Forest. It is legal to fly UAV in the National Forest. There are lots of very interesting things to film.
First thing is to start building a workflow. Some of my equipment is new and other is dated. First step should be updating all of the firmware. I will list things I think I need to do and criticisms and corrections are welcome. JimP
They are very useful. I use one for Amateur Radio antenna tuning.
Just for fun I put a 915Mhz vertical dipole antenna from TE Connectivity (IOW, known good) on the NanoVNA and as expected got very good results. The Graph is from the Nano Saver PC application.
This is 868MHz antenna as evident by SWR dip on 865MHz, I wouldnāt call 1.8 SWR at desired frequency particularly good. It should be 1.5 or less.