Example screen used in LB jar applet.  

Link Budgets for Digital Comms Links 

A simple link budget utility was developed for International Space University (ISU) workshops.  This software was written as a Java application to run on laptops or PCs. It allows link budgets to be calculated and provides some examples.   The software is no longer on the UniSA web site, but a version of the jar file is available here.  It can be run from a command window eg
"java -jar lb.jar"  You may need to set suitable permissions. You might also download this short pdf tutorial explaining EIRP, G/T, link margins etc.  

For greater portability, I've recently made an Android app that offers similar link budget calculations, plus examples.  Please see more information here.

Here is a sample LB for  70cm inter-cubesat communications, illustrating some typical parameters:  

Carrier frequ    435 MHz
Link distance    1000 km
Required Eb/N0   16 dB
Tx power         0.2 W
Tx gain          0.0 dBi
Tx EIRP          -7.0 dBW
System Temp      500 deg K
Rx ant gain      0 dBi
Rx G/T           -27.0 dB/K
Atmos&Track loss 1 dB
Modem loss       1 dB
Given rate       1.20 kbit/s
Free space loss  -145.2 dB
Requ C/N0 is     46.8 dB-Hz
Available margin 0.6 dB