EmonTX wireless reliability

Hi, 

first : apologies for my bad english !
I try to use my EmonTX to monitor power consumption and PV power production.
RFM12B seems to me no very reliable!
Please have a look :
-------------------------------------
RF12B demo Receiver - Simple demo
Node: 10 Freq: 433Mhz Network: 210
329  0.00  Time :  0:02:34 
407  0.00  Time :  0:03:16 
406  0.00  Time :  0:03:37 
2128  0.00  Time :  0:05:12 
2858  0.00  Time :  0:16:56 
2753  0.00  Time :  0:17:28 
2549  0.00  Time :  0:20:47 
1640  0.00  Time :  0:26:13 
1006  0.00  Time :  0:33:14 
658  0.00  Time :  0:36:02 
582  0.00  Time :  0:37:27 
590  0.00  Time :  0:40:04 
535  0.00  Time :  0:41:08 
793  0.00  Time :  0:41:29 
335  0.00  Time :  0:42:00 
278  0.00  Time :  0:44:27 
273  0.00  Time :  0:44:38 
268  0.00  Time :  0:44:59 
309  0.00  Time :  0:47:47 
287  0.00  Time :  0:49:33 
387  0.00  Time :  0:55:09 
400  0.00  Time :  1:06:44 
315  0.00  Time :  1:08:40 
2475  0.00  Time :  1:19:00 
1068  0.00  Time :  1:54:25 
839  0.00  Time :  2:03:43  
--------------------------------------------------
My EmonTX led flash every 10 sec. Battery voltage is 2V947. Antenna length 170mm vertical polarisation.
Receiver is a Nanode V5 antenna 160mm vertical located 6 meters away but one floor above with a concrete floor !
I use emonTx_3CT_Example_.pde in my EmonTX and Rx_SimpleRFM12B_demo.pde (modified for displaying time stamp) in my Nanode
25 good receptions in 2 hours !!.
Where to search to solve ?

Is it possible someone more proficient then me to write a small sketch for EmonTx for sending the values of all inputs and an other sketch for Nanode (or RFNanode) for displaying these values in the internal terminal. I am a newbie with Arduino and for the moment, unable to do that.

Many thanks in advance for your greatly appreciated help.

Regards from Belgium

Jacques