Measuring signal strength on the RF12

I have a jeenode on top of the compost bin - the signal is very weak.  So dug around and found someone was using the software rf12_getRSSI function to create a crude 7 level signal strength.  I have got so far with my new found knowledge - able to get the following:

The data has been truncated from 20 to 10 items 'cos I am not really interested in all the junk.

Clearely the 8,10,14db is wrong - it is simply reporting the RSSI and not translating it - and this is where i have the problem.

First of all I take no credit for the idea - it is simply hacked from http://forum.jeelabs.net/node/1470.html

Without knowing how to use the version control properly or how to do patching I took the following approach:

1) I got a new version of RF12.cpp, RF12.h, RF12sio.cpp and RF12sio.h from https://github.com/jcw/jeelib/tree/rf12mods

(didn't know if I needed the last two files ) and simply poked them into the Arduino library (getting a red exclamation mark for my troubles)

2) Hacked the patch from the above forum link

for (byte i = 0; i < n; ++i) {

Serial.print(' ');

Serial.print((int) rf12_data[i]);

}

Serial.print(" (");

Serial.print(rf12_getRSSI(), DEC);

Serial.println("dB)");

into HAHcentral from

http://livebox-hah.googlecode.com/svn/trunk/userapps/arduino/HAHCentral/ which I believe is the 

source for HAHCentral_nocfg.cpp.hex

3) It compiled much to my surprise and the result is above.  I now  use Arduino ERW 1.0.5 because that shows me where

the hex path is and I can upload the new sketch via the livebox without turning it all off.

The problem is that I would like to try and use the code from his patch which would seem to go into RF12.cpp

// return signal strength calculated out of DRSSI bit
+int8_t rf12_getRSSI() {
+    if (! drssi & B1000)
+        return 0;
+    
+    const int8_t table[] = {-106, -100, -94, -88, -82, -76, -70};
+    return table[drssi & B111];

This will translate to a range from -70dB to -106 dB which is right.

I can't find out how to edit RF12.h without injecting loads of <CR><LF> which the compiler doesn't like.  Arduino 1.0.3 

won't edit this file type.

Any ideas?  Will this approach work? I'm a bit worried about the B1000 stuff whatever that is!

I think having signal strength is useful to help diagnose difficult path tranmission cases - I can work with the 1 to 7 levels reported but would like to make it look right - who knows it may get incorporated and I can get rid of my exclamation marks.

Regards

Kim