Radio Microphone Switcher (When you have two radios but wish to use one microphone )

VK2RK

Active member
(This is a concept design as such is theoretical, final design will include any other solutions as required)

When you have two radios and wish to use one microphone.
I decided to design such a device, in my limited desk space this will allow me to use my studio microphone and PTT control on the selected radio.

The design uses a CD4066 this device consists of four independently controlled switches that will handle both a DC voltage and AC signals. The PTT current from an ICOM radio I measured to be 1.5 mA the CD4066 will sink 10 mA so this is well within the ability of the device to handle the PTT current.

The device is powered from the radio 8 Volt source present on the microphone socket, note that two diodes are used to source from either or both radios isolating one radio from the other. This in case one of the radios is not turned on, the switcher will still operate.

The CD4066 operation is straightforward, when a high is applied to the Control the switch is closed so if Ctrl A is high switch A is closed and so on.
with this I can steer the Audio and PTT signal from one radio to the other.

The diodes on the PTT lines are there to protect the CD4066 in case of switching inductive loads on the PTT
I may need to apply some RF suppression to stop any RF getting into the circuit.

This circuit will work on other brand radios as long as the PTT current is less that 10 mA.


Microphone switcher.jpg
 

VK3ZYZ

Moderator
Staff member
This will be very handy,
One addition I thing may be for a bicolour LED (or 2 LEDs) for a red and green indicator to show the selected set.
 

VK3YNV

Administrator
Staff member
What about using opto couplers for the PTT switching, that way the 4066 only has to switch the led current through the opto.
An added bonus is you could handle +ve or -ve PTT switching radios.
 

VK2RK

Active member
What about using opto couplers for the PTT switching, that way the 4066 only has to switch the led current through the opto.
An added bonus is you could handle +ve or -ve PTT switching radios.
Understand what you suggest but the 4066 can handle up to 10mA per switch so don't see the need to sink more current, beside the PTT current in the ICOMS is only 1.5 mA I suspect most other radios will be well with in the 10 mA range.
4066.jpg

This will be very handy,
One addition I thing may be for a bicolour LED (or 2 LEDs) for a red and green indicator to show the selected set.
You must have telepathically sent this to me, this morning I did add the LED's next post shows the final circuit with the PCB
 
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VK2RK

Active member
This is the final version (LOL... how many times have I said this and later made changes)

Mic_Rad Switcher.jpg
 
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VK2RK

Active member
Ray made the point of switching PTT using positive voltage as required on some radios,
The 4066 does not care as to the polarity of the level been switched, the only limitation is the current that can flow in the switch

For those that wish to look in more detail the properties of the 4066 here is the data sheet.
 

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VK3ZYZ

Moderator
Staff member
I just spotted the LEDs. You may need series LED resistors to raise the control voltage as the LEDs connected as shown will clamp the control voltage to around 2V and I think the 4066 needs higher than that.
 

VK2RK

Active member
I just spotted the LEDs. You may need series LED resistors to raise the control voltage as the LEDs connected as shown will clamp the control voltage to around 2V and I think the 4066 needs higher than that.
Absolutely, I realized my mistake, too eager to add the LED's. Presently doing some current calculations to raise to the gate voltage of 4V for a High

(EDIT Diagram is now amended )
 
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