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.

The design

So we calculated the design (with help of this calculator), 

Materials used

  • aprx 50cm of 2mm diameter brass or copper wire
  • 1 x BNC chassis part (no SMA of N was availible in the junk box) :-)

 

Building steps

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.

LoRA J-Pole antenna - simulation

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

 

 

Conclusion

The higher the better ;-)


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