The BIG and SMALL ANTENNA topic part 2


#1

previous topics : The BIG and SMALL ANTENNA topic part 1

populair for GateWays :

populair for Nodes :

DIY :

Web tools :

info :

SNR - https://en.wikipedia.org/wiki/Signal-to-noise_ratio
RSSI - https://en.wikipedia.org/wiki/Received_signal_strength_indication
DB - https://www.circular-wireless.com/en/conceptos-sobre-antenas/comprendiendo-los-decibelios/


The BIG and SMALL ANTENNA topic part 1
Outside Antenna
(Michael Graff) #2

Can you post the dimensions you used for the sections as well?


The BIG and SMALL ANTENNA topic part 1
(Tony Smith) #3

@skandragon, no problem, here is a link to an earlier post with the link to GitHub where the drawings are kept. The BIG and SMALL ANTENNA topic part 1


#4

diy Archimedean spiral antenna for RTLSDR


(Michael Graff) #5

I used the PDFs and such, but for some reason the antenna did not come out well at all. For instance, it was at least 100 MHz lower than it should have been, using the 915 Mhz lengths. I’ll have to experiment.


(Tony Smith) #6

While I run 915MHz I built the 868MHz version and found it tuned at 840MHz. (refer post earlier in June) Had trouble adjusting the tuning frequency. Since I could not get repeatability I moved to a Colinear Coaxial antenna with a 1/4wavelength at the bottom with 8 half wavelength sections above. This worked much better but more effort to make. So I’m at a cross-roads, do I spend more time building jigs which might give me repeatability or do I focus on cutting coax for a coax colinear???


#7

Well build ground plane for 25 Euro:

https://stefan.schultheis.at/category/amateurfunk/dipol/


The BIG and SMALL ANTENNA topic part 1
#8

gpmall3dprinted


#9

I’m using this Omni Antenna, 5 dBi, with quarter-wave sleeve balun (german: Sperrtopfantenne).
All parts of the antenna are grounded.

https://www.wimo.com/rfid-antennas_e.html#18003868


(S54mtb) #10

I designed small and simple antenna for end devices:
http://e.pavlin.si/2018/06/29/small-normal-mode-antenna-for-868mhz/

7 helix antennas can be prepared from about 20cm of coaxial cable, Tools needed are “common” from every garage.


#11

LORAWAN Antenna SWR measurement (DIY)


(Ryan Walmsley) #12

Looking for recommendations for a reasonably priced indoors antenna. I tried building the DIY Colinear one on the TTN Labs as I don’t have an SWR Meter I’m not sure if its that tuned. I do have the parts to build the simple ground plane antenna instead (Just a case of chopping the current one’s copper down).

Currently it gets around 200M and was wondering if a better antenna would get it to around 300-500M. Its actually very high already however is indoors and can’t be moved outdoors.


#13

you mean the distance to your node ?


(Ryan Walmsley) #14

Indeed around 200 meters when mapping. While I don’t expect as far as my other gateway which gets a few KM as its outdoors.
Screenshot%20from%202018-07-05%2022-47-14

And that’s with https://www.thethingsnetwork.org/labs/story/homemade-outdoor-868mhz-antenna


#15

is there a long cable between gw and antenna ?


(Ryan Walmsley) #16

Around 15CM link. RAK831 one end, N connector the other.

Only thing I can think is I didn’t “microwave test” the pipe I used to encase it. Could be that.


(Amedee) #17

This doesn’t look right…
Obviously it depends on your construction and environment, but my indoor gateways with the stock 2dbi IMST antenna give me at least 1km (urban area)


#18

I agree… check short cable @ connectors (sometimes male/female error) / switch antenna for whatever just to test


(Rustie0125) #19

Hey Peeps,
Glad to have found this thread! after a lot of reading and experimenting, my finds are as follows.

Cheap “Super Gain” Fiber glass antenna’s from ebay/aliexpress. -Crap!
Diy and Bought Col-linear without radials -Crap!
J Pole and Gap antenna- Crap!
Diy and Bought Co-linear with radials added- Okay!

Diy and Bought 868Mhz GPA - best ! did a range test with a 1/4 wave GPA and got 4.2Km at -120 Rssi and -5 SNR in busy urban area. this can be bettered but the issue is on the node side(antenna not tuned).

All antenna’s was tested for SWR, and peak frequency.

Summary
To be honest, Im at a loss as to where to go from here. The 868Mhz GPA antenna tuned for 868.3 ( not 915Mhz) offers the best Price-Size-Gain Ratio!
I have successfully miniaturized the 1/4 GPA antenna and it will now fit into a 75mm Diameter x 100mm PVC pipe for protection for outdoor use.

If someone has a better antenna for use on base-station please comment would love to test it!

GPA%20antenna


(LoRaTracker) #24

Better antennas for base stations, i.e. with more gain, is not without its issues.

Since the gateway is probably already transmitting the legally allowed power, if you attach a gain antenna, you need to reduce the power transmitted.