DIY 433MHz UHF receiver antenna. TREX build update 3

This antenna is going to be used for the TREX 450 helicopter build and will be placed on the tail. The RC receiver will be located near the frame, will be using a FLYTRON receiver. This rx antenna can be used on any UHF LRS system, like EzUHF, Rangelink, Orange OpenLRS.

DIPOLE antenna, is essentially two wires(elements), a top and bottom.

To determine the length of the wires for your desired frequency: Take the speed of light and divide by the Hertz and it will give you the wavelength. Here we are building a 1/2 wavelength antenna so we divide by 2 for our whole antenna size. This is the basic version.

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The speed of light = 299,792,458,000 millimeters per second’ish
433 megaHertz = 433,000,000 Hertz
299,792,458,000 divided by 433,000,000 = 692.361334873mm. This is wavelength.
692.361334873 divided by 2 = 346.180667437. This is how tall the whole assembly will be in mm.
346.180667437 divided by 2 = 173.090333719. This is how long each of our two elements will be in mm. 173mm each.
but the speed of light through our atmosphere is slowed by gasses and wire losses. So we multiply the 173mm by .95, = 164mm atmosphere corrected. If you are in a vacuum of space, you would use 173mm * wire losses. We’ll use 164mm. “Velocity Factor”. I’ll also note that the VF can vary depending on what cabling you use and that the SWR should be tested to make sure your antenna is resonating at the correct frequency. Speed of light VF of 91% to 95% is the range we will see with our gear and environments, thus our antenna element lengths may vary from 159mm to 164mm and is why SWR tuning is required to make a great antenna, all I made today is a good antenna.

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Parts used:

I used solid core, .035″ welding wire, it works really well. But if you want more durability but less performance you can use 22ga multi-stranded wire.