Path: utzoo!censor!geac!torsqnt!news-server.csri.toronto.edu!cs.utexas.edu!bcm!rice!uw-beaver!milton!whit
From: whit@milton.u.washington.edu (John Whitmore)
Newsgroups: sci.electronics
Subject: Re: WIDE BAND LOW NOISE SMALL SIGNAL VHF/UHF AMPLIFIER
Message-ID: <15415@milton.u.washington.edu>
Date: 29 Jan 91 23:03:07 GMT
References: <1991Jan29.185705.26404@uncecs.edu>
Organization: University of Washington, Seattle
Lines: 25

In article <1991Jan29.185705.26404@uncecs.edu> crisp@uncecs.edu (Russ Crisp) writes:
>
>Hello.
>I'm interested in either building or buying a very low noise,
>high gain wide band preamplifier to use with my scanner.  I have
>a Monitenna up about 40 feet, and I'm currently using a plain ole'
>tv booster with fair results.  I'm interested in frequencies
>from around 30Mhz to around 512Mhz.  

	Avantek and Mini-circuits and Signetics all have VHF/UHF
amplifiers with moderate gain and low noise at low cost, BUT
you will want to limit the bandwidth on input to prevent front-end
overload.  The 60 Hz pickup on an antenna can easily be a few dozen
volts, and that will saturate almost ANY amplifier you can name.
	That said, just use an IC integrated amp (these are typically
four-pin pillbox package devices) or a good low-noise FET biased
for 50 Ohm input impedance (U310 is recommended for this).  If you
use the FET, you'll get slightly better noise figure, but the output
of the monolithics is 50 Ohms; the FET will require some matching.
The capacitance of the FET is ignored if you use grounded-gate
configuration, but can be part of your matching network in a
grounded-source design (for highest gain).
	Posting your query on rec.ham-radio might be productive...

	John Whitmore