Message 27611 in TECH.WW
From: G8MNY
Date: Sun, 09 Aug 26 07:52:00 Z
Newsgroups: TECH.WW
Subject: Toggle PTT
Message-ID: <1538_GB7CIP>
Path: N2MH4|VE3KPG|N9PMO|CX2SA|ED1ZAC|GB7CIP
R:260809/0805Z 35126@N2MH4.#SENC.NC.USA.NOAM LinBPQ6.0.24
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From: G8MNY@GB7CIP.#32.GBR.EURO
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
----------------
Watchdog & led flasher
----------------------
--------------
2 wire electret.
4K7 22K ===
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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