Antenna LTE (4G) 800 MHz

thingiverse

First: I do not really know, what I am doing here;) I just followed the instructions of the original thing and looked at the remixed ones. Then I decided, that I wanted to create a version, optimized for 800 MHz. 1800 are out of reach here and so an 800 MHz optimized antenna would probably have more gain - or it could be smaller. So I used the calculator: https://hamwaves.com/lpda/en/index.html The frame fits easily onto a 20 by 20 cm printbed. And surprisingly – it´s magic! – it all seems to work :) You have to print four of the frames. As a stand I used a 12 mm aluminium tube and an heavy door stopper, that I glued the foot to. Further you need copper wire 1.5 mm and two little 3 mm screws (to fix the brackets). Use zip-ties to connect two frames. I had some 5 m coax-cable (50 ohm, 5.6 mm diameter) with SMA male connectors as they where needed by my router, cut from an old LTE antenna. Instead of gluing the copper-wire I used my welding iron to heat the copper. Then, the PLA melts and by pushing the wire down with some pliers (to cool it the same time), the wire is „glued“ to the construction. I did this beginning at one end and going forward every about 5 seconds for an inch. Finally the wires have to be soldered in the middle. After finishing the four frames, take two, put the coax-cable in the middle and fix all with the zip-ties. The inner of the coax is soldered to one of the middle wires at the front of the antenna, the shield is soldered to the other one. The holes in the brackets are formed in a way, that you can slip the SMA-connector through them. The gain should be arount 8 dBi when you look at the table at hamwaves.com. UPDATE: I installed my old router with a better possibility to monitor the signal strength. With that I experienced, that the gain is even higher, when I mount the two antennas besides each other instead of one over the other. The distance should be at least 40 cm, which is a bit more than the wavelength. Mounted that way and with a low-loss cable the win is great in comparison to the inner antenna of the router (Speedport Hybrid) that had a RSRP of -104 dBm, with a propperly aimed printed antenna the RSRP was -95! ---- Lowest frequency f₁ = 800 MHz Highest frequency fₙ = 875 MHz Diameter of the shortest element ⌀ = 1.5 mm Characteristic input impedance Zc_in = 50 Ω Taper τ = 0.940 Optimal relative spacing σₒₚₜ = 0.177 Chosen relative spacing σ = 0.060