/AudioToResistance

Audio input decreases FET resistance. Simple, stray RF suppression, designed as a PTT circuit.

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Copyright (C) 2013 mirage335
See the end of the file for license conditions.
See license.txt for AudioToResistance license conditions.

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All parts can be found at HacDC. Please drop by!

hacdc.org

__Usage__
Audio in at CONN1, audio transformer between CONN1 and CONN2, on/off switching at CONN3. Useful for Push-To-Talk systems.

__Design__
Placing a 47nF capacitor (C1) at input to diodes prevents stray rectification.
Use of appropriately valued non-polarized capacitors maximizes VHF/UHF suppression.
Transformer T1 prevents stray rectification problems, particularly those in the radio itself. It should be a step up transformer, but may not be necessary in some cases.
NPN transistor offers superior characteristics for driving CMOS inputs. Most TO92 case enhancement mode N-Channel JFETs are pin compatible for other applications.
Transistor will be switched on and off repeatedly from villard cascade ripple. When driving CMOS inputs with pull up resistors, capacitor C5 will smooth this ripple. However, in other applications where a JFET may be used, a peak detector following the voltage multiplier will eliminate ripple, at the cost of higher input drive requirements.

__Copyright__
This file is part of AudioToResistance.

AudioToResistance is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.

AudioToResistance is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with AudioToResistance.  If not, see <http://www.gnu.org/licenses/>.