Xref: utzoo sci.electronics:4359 rec.ham-radio:7090 Path: utzoo!utgpu!watmath!clyde!att!rutgers!gatech!cwjcc!mailrus!nrl-cmf!ames!elroy!peregrine!ccicpg!cci632!dvh From: dvh@cci632.UUCP (David Hallidy) Newsgroups: sci.electronics,rec.ham-radio Subject: Re: RF preamp techniques Keywords: preamp, splitter, combiner, noise figure, gain Message-ID: <23211@cci632.UUCP> Date: 30 Nov 88 20:57:07 GMT References: <2038@nunki.usc.edu> Organization: CCI, Communications Systems Division, Rochester, NY Lines: 22 I wouldn't recommend a 3dB splitter before either preamp. If you do this, you are automatically degrading the system noise figure by the 3dB loss of the splitter- same as if you had 3dB of cable loss between the antenna and the preamp. I believe the answer is to build (or purchase) a wider bandwidth preamp. Avantek has an application note describing a GaAsFET preamp with about a 0.4dB NF and about 20dB gain which has an untuned input (matched to 50 ohms) using the ATF10135 device and which will have excellent performance over AT LEAST 100 MHz. Check it out. Put the preamp as close as possible to the antenna and then run about as much coax down to the receiver as you want- you'll have plenty of excess gain. This eliminates all the splitters and combiners. In fact you could put a splitter after the preamp and use it to drive a couple of receivers and still have enough gain for both. Hope this helps. 73 Dave KD5RO