Xref: utzoo sci.electronics:4351 rec.ham-radio:7066 Path: utzoo!utgpu!watmath!clyde!att!osu-cis!tut.cis.ohio-state.edu!cs.utexas.edu!sm.unisys.com!oberon!nunki.usc.edu!cyamamot From: cyamamot@nunki.usc.edu (Cliff Yamamoto) Newsgroups: sci.electronics,rec.ham-radio Subject: RF preamp techniques Keywords: preamp, splitter, combiner, noise figure, gain Message-ID: <2038@nunki.usc.edu> Date: 29 Nov 88 20:22:23 GMT Reply-To: cyamamot@nunki.usc.edu (Cliff Yamamoto) Organization: University of Southern California, Los Angeles, CA Lines: 32 Greetings I have an arbitrary question regarding RF preamps, splitters, and combiners. Does the following look feasible? ______________ _____ | GaAs FET amp | \ | / __________ | 400-450 Mhz | __________ V | 3 dB |------|______________|------| 3 dB | |____| splitter | _______________ | combiner |----> to receiver |__________|------| GaAs FET amp |------|__________| | 450-500 Mhz | |______________| Would there be too much noise introduced by the splitter and combiner to be of any use? Or is it better to select one amp and operate it at 450Mhz without the splitter/combiner? If I use ONE amp, is it possible for an amp to have a negative dB effect (i.e. attenuation) at the extremes? Example : if I wished to monitor two signals at 425Mhz and 475Mhz would: 1) the above diagram using two amps having a noise figure of 0.5dB and some gain X dB be better OR is 2) one amp with a 400-500Mhz range, but higher NF and lower gain better. (tuned to center of 450Mhz) In short my question is : What do you do if you want to pre-amplify a wide frequency range with high gain and low noise, but DO NOT have an amp with such a wide BW available. Cliff Yamamoto ------------------------------------------------------------------------------- Internet : cyamamot@castor.usc.edu castor!cyamamot@oberon.usc.edu cyamamot@nunki.usc.edu cyamamot%nunki.usc.edu@oberon.usc.edu