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From: Tony Fonseca Date: November 4, 1996. Subject: TX Delay Modification For The YAESU MH-27 DTMF Microphone I didn't like to have to depress the PTT switch with one hand and the DTMF buttons with the other hand especially while driving so, I modified my mike to automaticly transmit the DTMF code and have a one and one half 1.5 second TX delay if the DTMF buttons are to be used. HERE IS THE MODIFICATION: Open the microphone by removing the three screws on the back. You will have to lay the componants properly under and above the cuircut board. They fit in there quite nicely. I used longer leads on the 2n2222 transistor so it could be tucked nicely under the cuicut board beside the up/down buttons. THE PARTS YOU WILL NEEDED: 1 - 2.2K ohm resistor. 1 - 10 Megaohm resistor. 1 - 10 ufd 16 volt electrolytic capacitor. 1 - 2N2222 NPN transistor or equivalent. Solder one end of the 2.2K resistor, one end of the 10 megaohm resistor and the positive terminal of the 10 ufd 16 volt electrolytic capacitor to the base of the 2N2222 transistor. Solder the other end of the 2.2K resistor to the anode side of the LED D1. Solder the other end of the 10 megaohm resitor, the negative side of the 10 ufd capacitor and the emitter of the 2N2222 transistor to ground. The ground terminal is pin 5 of the 8 pin connector. One side of the PPT switch is also grounded to pin 5. Solder the collector of the 2N2222 transistor to pin 3 of the 8 pin connector. Pin 3 is also connected to the other side of the PTT switch. To vary the time delay, change the value of the 10 megaohm resistor. The higher the valu, the longer the delay. This Modificatin Works Great. Enjoy Easier Mobiling. 73 Tony Fonseca, The VE7ACF |
