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IZ3LSV

[San Dona' di P. JN]

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G8MNY  > TECH     30.03.11 23:31l 109 Lines 3617 Bytes #999 (0) @ WW
BID : 11400_GB7CIP
Read: GUEST
Subj: Toggle PTT
Path: IZ3LSV<IK2XDE<PY1AYH<PY1AYH<CT1EJC<ON0BEL<GB7CIP
Sent: 110330/2158Z @:GB7CIP.#32.GBR.EU #:11400 [Caterham] $:11400_GB7CIP
From: G8MNY@GB7CIP.#32.GBR.EU
To  : TECH@WW

From: PA3BNX@PI8SHB.#NBO.NLD.EU                   (New Apr 06)
(8 Bit ASCII graphics use code page 437 or 850, Terminal Font)

Hello All,
Subject: Handsfree ptt-switch for mobile use.
---------------------------------------------------
Using a vox is not nice in a car because it goes transmitting when it hears
sounds.

Keeping a ptt switch pressed while driving & stearing is also unsafe.

Thats why I decided to make a large toggle switch on the dashboard with a Red
5mm flashing PTT led & a Mic gain control.

Construction of toggle switch
-----------------------------
I made from double clad PCB about 3 x 6 cm & a microswitch as a nice toggle
switch. I did solder a small hange to the PCB& tinned box. And I mounted the
microswitch in the metalbox & only the handle pin is pushed when the PCB piece
is pushed. I did painted it red hi.
So I have a nice big easy to push PTT switch.

Circuit diagram
---------------
I have made a small metalbox with a large pushbutton (S1) on it.
And a big bright 5mm led.
The pushbutton is connected to a toggle circuit.
The output of the toggle circuit is connected to a watchdog circuit which
drives a PTT transistor to switch the tranciever, & also the LED flasher
circuit.
Use a 5 mm highbright led so you see it very easy flashing when transmitting
without having to look at the tranciever.

So push S1 & PTT is on for maximal 3-5 minutes & the led flashes. After 3-5
minutes the watchdog switches off the mobileset from transmitting.
(use 100-220uF).

So if something happens your rig is not any more transmitting a carrier for
hours.

Mount the small box some where on the dashboard next to the steering wheel so
you can easy see the led & push the S1 Switch.

Further I mounted a small electreet at the sunscreen for getting the sound.

I also mounted a small mic-preamp with a gain potentiometer in the
ptt switchbox so I can adjust the audio level when driving.

PTT toggleswitch
----------------
100n1MĿ
   ===   S1        10106 or 4093 etc.
        o         
 Ĵ    \  \       \
__ 1n  Ĵ `>oĴ `>o>to A
   ===     /'       /'    
    100k

Watchdog & led flasher
----------------------
                 +Vcc 915V
                   
A              3M3 __ 1N4148
                 /_\                    o Ptt
  _                   _ 4093     BC547    
Ĵ `\     100u     Ĵ `\            /   __
  & )o1kĴĴ  & )o10kij    /_\
Ĵ_,/         +      Ĵ_,/'         \ e   1N4007
    4093                           4k7      
 Ground)o
                               
 
    _
 Ĵ `\      _ 4093
     & )oĴ `\
 Ĵ_,/      & )o1kĿ
          Ĵ_,/   +      __
1M        100k     === 1uF  \_/ Red 5mm Led.
         Ground

Micampliflier
--------------
2 wire electret.
     560+Vcc 915V
                               10uF +
    4k7      22k                     ===
                741 or LF353       __
             Ĵ\     + 10uF
      u1     100p===`>oĴĿ
()Ĵ4k7)Ĵ/'       
  ===    +Ĵ               5k
   1nF  ===    47k   pot<o Rig Mic
      10u 22k                 
 o

Gain = about 10x

I did not wrote the pin numbers of the ic's to it yet.

73's from PA3BNX@PI8SHB.


Y don't U send an interesting bul?

73 de G8MNY @ GB7CIP
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