emonTx V3 Antenna Testing

Today we did some quick testing regarding using different antennas with the emonTx V3. 

Four antenna options were tested (Farnell part numbers listed for SMA antennas) :

Note: the graph sub-title has a typo, it should read 'RFM69CW', 'CRW' module does not exist.. At least to my knowledge! 

It was found that the wire-whip antenna as shipped by default with the emonTx V3 performed best. 

However using an SMA could be preferable in some environments; it's more robust and can  be extended easier. 

Now we have a way to measure RSSI (received signel strength indicator) using  an rfm69cw module we plan  to  do some more antenna and range testing. I'm interested to test to see how many db we're loosing in the antenna pcb trace from the module to the RFu328 then the emonTx V3 pcb trace then finally into the 90 degree sma connector. In future version will probably but the rf module and MCU directly on the PCB keeping the antenna trace as short as possible and use an edge mounted sma connector (these are also cheaper and easier to solder in manufacture). 

For more info on the test see the emonTx V3 wiki page: