[Moon-net] LNA 144 ATF54143? *Jerry Kleker* w7qx at msn.com /Mon May 29 12:49:54 CDT 2006/ * Previous message: [Moon-net] LNA 144 ATF54143? <005352.html> * Next message: [Moon-net] 10GHz EME <005376.html> * *Messages sorted by:* [ date ] [ thread ] [ subject ] [ author ] ------------------------------------------------------------------------ Hi Dom, When we tune for best NF, aren't we optimizing under the same conditions as the conditions presented (at 144) to the LNA by the antenna? I agree that the LNA "input" is not 50 ohm resistive at 144 but it may be at 140. As I recall, I think that Peter, G3LTF, uses a different Noise Generator on each band and each of the Noise Generators uses a tuned circuit which presents a reactive component to the LNA, off of the desired frequency. This simulates the reactive components, that are presented by the antenna off of the desired frequency. 73, Jerry W7QX ----- Original Message ----- From: DEHAYS Dominique> To: Peter Hansen> Cc: moon-net at list-serv.davidv.net > ; Moon-net-bounces at list-serv.davidv.net > Sent: Monday, May 29, 2006 12:54 AM Subject: Re: [Moon-net] LNA 144 ATF54143? With other words I agree totally on RL match on input side, does NOT coincide with optimum NF. Gm Peter , 1) It is possible to get good RL and good NF at the same time using feedback BUT feedback is detrimental for stability . The well known preamp by PA3BIY I think , manage to get both , but at the cost of questionnable stability. If one is lucky , he can use it without oscillations ( but you know Murphy?) 2) In our application ,iIt is not necessary at all to get good match , the only reason for it is to reduce gain error during NF measurement.( for more info abt gain error read DJ9BV article on NF measurements , F5VHX also wrote a nice one , but I don't know wether it is available on the net) 3) I think that panfi accuracy is not good enougth to get reliable measurement , the measurement error is higher than the expected NF. 73's Dom/F6DRO _______________________________________________ Moon-Net posting and subscription instructions are at http://www.nlsa.com/nets/moon-net-help.html ------------------------------------------------------------------------ * Previous message: [Moon-net] LNA 144 ATF54143? <005352.html> * Next message: [Moon-net] 10GHz EME <005376.html> * *Messages sorted by:* [ date ] [ thread ] [ subject ] [ author ] ------------------------------------------------------------------------ More information about the Moon-net mailing list