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QRZ! Ham Radio 19
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yaesu_mic.txt
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2001-11-01
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From: Tony Fonseca <afonseca@kitimat.sno.net>
Subject: TX delay mod for the YAESU MH-27 DTMF microphone
November 4, 1996.
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 mod.
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.
Parts needed: 1 each 2.2K ohm resistor
1 each 10 Megaohm resistor
1 each 10 ufd 16 volt electrolytic capacitor
1 each 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 mod works great. Enjoy easier mobiling.
Tony, VE7ACF @ VE7DRA.#NWBC.BC.CAN.NOAM
afonseca@sno.net (email)
http://www.sno.net/afonseca/ (web page)