LoRA J-pole antenna
LoRA J-pole antenna
Hamradio is all about experimenting, so why not do that for my LoRA WAN / TheThingsNetwork setup?
At my local Hamradio club (Veron/VRZA Twente) a fellow Ham, was wondering if the J-pole design (very commen antenna in the hamradio world) would also work.
So we calculated the design (with help of this calculator),
- aprx 50cm of 2mm diameter brass or copper wire
- 1 x BNC chassis part (no SMA of N was availible in the junk box) :-)
Well there are a few but here are the results :-)
SWR measurment result
After the building we tested it with a RigExpert AA-600 (which when connected to the computer can work up to 1.4Ghz) from the fellow ham and the SWR dip was right on the 868Mhz.
Can't wait to test this one in the field.
So I have tried to simulated a 868Mhz J-Pole in freespace and on variouse heights above good ground.
For these simulations I used the 4NEC2 software which can be download here. Tutorials in 4 parts can be found here : part0, part1, part2. Another good tutorial set is this serie of 4 article publisched in QST : part1, part2, part3, part4 (but off-course you can also google for "NEC antenna tutorial pdf").
J-Pole in freespace
The NEC file : 868_jpole.nec for this simulation.
CM CE SY Height=0.25 'Height above ground in m SY Lambda=0.33 SY Spacing=0.008 SY Feedpoint=0.008 SY Wire=0.002 GW 1 10 spacing 0 height+lambda/4 spacing 0 height+feedpoint Wire GW 2 5 spacing 0 height+feedpoint spacing 0 height Wire GW 3 5 spacing 0 height 0 0 height Wire GW 4 5 0 0 height 0 0 height+feedpoint Wire GW 5 25 0 0 height+feedpoint 0 0 height+3/4*lambda-feedpoint Wire GW 6 5 0 0 height+feedpoint spacing 0 height+feedpoint Wire 'Feedpoint GE 0 GN -1 EK EX 6 6 3 0 1.000000 0 0 FR 0 10 0 0 868 0.1 RP 0 91 120 1001 0.000 0.000 2.000 3.000 5.000E+03 EN
The NEC file has 5 variables :
- Height : variable (in meters)
- Lambda : full wave length
- Spacing : space between 3/4 and 1/4 lambda wire
- Feedpoint : connection point
- Wire : wire radius
J-Pole 0.25 m above realground
J-Pole 0.5 m above realground
J-Pole 1 m above realground
J-Pole 5 m above realground
The higher the better ;-)