[werk_ag]

Hamix, you can test maximum TX RF range in a very simple way.

The TX led on the RX board blinks when a data packet is sent to the WD units, but as this data packets are relayed as soon as they are received, this led can also be used to check if we are receiving data from the TX units.
When there is no incoming data from a TX unit, the tx led on the RX board only blinks once a minute.
So, to test your TX unit RF range, just enable sending wind data (there is no need to have the wind instruments attached). The tx led on your RX board should blink at each 5 or 6 seconds (if you enable sending more data packets, it will blink more).

For this to work, you should have the Data Relay function active in the User Config options

Code:

// ---- Broadacasting Data Settings
#define Relay_Data       1  // 0= Disables Data Relay, 1= Enables Data Relay

The LED on the RX unit blinks only while RX unit communicates with PC. Does it?

One of the LED's yes, the other works as described above.

Anyway, I guess that memory of arduino nano can not allows to add some extra utilities, like TEST MODE.

That's right.

As referred by uncle bob the WD units have the ability to show you if any particular type of data packet is not been received. Of course you should be sure that the WD unit itself is in placed within the range of the transmitter of the RX unit