This is the same RF amplifier as used in the post-mixer amplifier.
This amplifier is used between the crystal filter and the diode mixer. Switch the 12 Volts on this amplifier when switching filters and it will help prevent feedthrough.
The 2N5109 amplifier can be simulated using the Serenade SV program. Information on using the program and simulating the amplifier can be found at "Simulating Circuits and Systems with Serenade SV", by David Newkirk, W9VES, January 2001, QST, Page 37.
The file for the amplifier is SerSV0101.ZIP at http://www.arrl.org/files/qst-binaries/
The Ansoft Serenade SV program can be downloaded at http://www.ansoft.com/about/academics/sersv/index.cfm
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