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   / mobilefish  

This is part 43 of the LoRa/LoRaWAN tutorial.

In this tutorial I will explain what a sleeve dipole antenna is.

Just like a dipole antenna, a sleeve dipole antenna has two elements.
One element is attached to the coax cable centre conductor.
The other element which is a metal tube (sleeve) is around the coax cable.
The sleeve is attached to the coax cable metallic shield.
The sleeve dipole antenna is also know under several other names: vertical sleeve antenna, coaxial sleeve antenna, etc.

The sleeve dipole antenna is a balanced antenna just like an ordinary dipole antenna.
The sleeve dipole antenna is fed by a coax cable which is an unbalanced feed line.
Normally in such a case a balun is needed.
In this case however the sleeve acts as a balun which counter the effects of the current returning back along the outer braid of the coax cable (antenna current).

The sleeve dipole antenna has the same donut shape radiation pattern as the normal dipole antenna (in free space).
A sleeve dipole antenna has a gain of 2.15 dBi (= 0 dBd)

When buying an antenna: Beware many antennas do not work as advertised!
Use an antenna analyser, such as the N1201SA, to check the antenna (see tutorial 40).

The modified sleeve dipole antenna B performance is compared with sleeve dipole antenna C.
More information about this end node, see:
https://www.mobilefish.com/developer/...
The end node uses the MCCI LoRaWAN LMIC Library:
https://github.com/mcci-catena/arduin...
The end node uses the following sketch:
https://www.mobilefish.com/download/l...

I have NOT modified the end node transmission power when using both sleeve dipole antennas.
Both sleeve dipole antennas were positioned at location A and in both cases two messages per minute were transmitted.
The logged data can be found at:
https://www.mobilefish.com/download/l...

One or more gateways were able to receive my transmitted sensor data, see:
https://drive.google.com/open?id=18SK...

If you look at the results you may notice there is no significant difference in the average RSSI values.
When using the modified antenna B it took 9 minutes to receive 15 messages.
When using antenna C, which is my reference antenna, it took 11.5 minutes to receive 15 messages.
This difference is caused by the limited number of measurements.
Once more measurements were taken there was no significant difference in time.
The Arduino sketch is configured to transmit 2 messages per minute.
In a perfect situation it should take 7.5 to 8 minutes to receive these 15 messages.

Looking at the results I can conclude that both sleeve dipole antennas performs the same.

If possible connect the antenna directly to the end node without the use of a coax cable.
Each connector/cable used is additional loss.
Watch out! An antenna which looks like this does not necessarily mean it is a sleeve dipole antenna.

A nice Youtube tutorial how to build your own sleeve dipole antenna:
   • Make Your Own FM Vertical Sleeve Coax...  

You get different results when the sleeve dipole antenna is folded or not.
Measure the antenna parameters in both states.

Check out all my other LoRa/LoRaWAN tutorial videos:
   • LoRa/LoRaWAN tutorials  

Subscribe to my YouTube channel:
   / @mobilefish  

The presentation used in this video tutorial can be found at:
https://www.mobilefish.com/developer/...

#mobilefish #lora #lorawan