There seems to be something that I'm missing in this preamp NF discussion. When I studied preamps and NF ~30 years ago, I thought the NF of the system of the first active device was the all-important thing. Whatever losses were between the antenna feedpoint and the preamp input (coax, connectors, relays) added to that.
Once that preamp brought up the S+N above a certain point, the NF of the amplifiers downstream were not near as important. Very low NFs, less than 0.5 dB, are easily obtainable with everything at room temperature. (I used GaAs FETs at 144 MHz, but there are even better devices today with lower NFs.) A couple of papers I just downloaded and skimmed over seemed to reinforce that. Look at the last three slides with screen shots of AppCAD in NoiseCalc mode at http://ve2zaz.net/Presentations/Downloads/VE2ZAZ_EME_Presentation.pdf and the paper at http://dpmc.unige.ch/dubus/8804-2.pdf There's much more to read on Google (I searched for *noise figure eme)* and in my library, but I still have the flu and I'm done for now. 73, Mike www.w0btu.com _________________ Topband Reflector Archives - http://www.contesting.com/_topband
