3/4 Wave Lora/Helium/Meshtastic Antenna 915mhz

I have recently gotten into Meshtastic and was disappointed by the cost of the nicer antennas and their lackluster performance(12 tested so far), So I decided to design one.

This is a 3/4 wave which will give a good radiation pattern and help extend the range of these low power radios. I made it to attach to any flat surface or to a 1 inch pvc pipe.

With the supplies below you can make 2 of these for around $15 total

The base of this antenna can also be used for most smaller antennas by cutting the threaded rod to the right length, Dipoles/longwire/etc..

4 x 10-24 Coupling Nuts

4 x 10-24 Standard Nuts (to be used at jam nuts)

1 x 3ft section of 10-24 threaded rod

1 - 3d printed design from above

RTV gasket maker, hot glue, or silicone for sealing the halves

4 Bolt/nuts for connecting the 2 case halves (6-32 bolts thread into the 1/8 holes in the case)

Zip Tie

Soldering iron / good flux core solder

Dremel tool with cutting wheel and sanding wheel

SWR Meter or antenna analyzer are important to have for tuning (I use this one)

Print the base from the attached STL File or at my Thingiverse link below

https://www.thingiverse.com/thing:6840500

Attach the Coupling nuts to your threaded rod(makes it easier to hold), sand one side to remove the plating, then use the cutting wheel to make a notch lengthwise down all four coupling nuts (this is a notch to lay the wire into for stronger solder joints)

Cut your threaded rod into an 8cm and 23cm length ( these will most likely be trimmed further)

Once the prep work has been done We are ready to assemble

Trim your coax, Shielding will go to the counterpoise coupling nut, core will go to the driven element coupling nut

Go ahead and get the coax in position and zip tie it to help hold it in place

Lay your wires into the notches we cut into the coupling nuts and solder them in place

Be careful on the heat, it can melt into the print and it needs to some to really seat the nuts

Once both sides are soldered, put the second case half on and secure it

Now you can thread the 23cm long rod into the Driven element coupling nut and the 8cm long rod into the counterpoise coupling nut.

To tune these these are the step I use

I twist both rods in until they are snug, adjustments will be made by loosening or tightening the allthread (the coupling nut give you 2cm of adjustment)

I use my antenna analyzer to watch the SWR's and move the counterpoise until the SWR hit their lowest point, then I move the driven element until the SWR hits its lowest point.

If the SWR's are still above 3 I will trim some off of the each element and repeat the process until I achieve around 1.5 or lower on SWR's.

Once I have gotten the SWR correct, I attach the jam nut to lock them into place(on the last 2 antennas this has lowered the SWR)

Seal off the block, Mount it up, have a blast.