Ham radio transceiver RF indicator circuit

This is a Ham radio transceiver RF indicator circuit. It is small and easy to build. Why it i

The application a Ham radio transceiver has 3 characteristic differentials are
Firstly is Monitored status or Sometimes called standby, Means to turn on the Ham radio transceiver to To listen or wait for a call from either one, will have signal in the Input signal or not.
Secondly is a status that signal came in turn on may called Receive signal (Rx)
Thirdly is a transmit signal status called Transmit (Tx)

How it works

Ham Radio Transceiver status indicator

In circuit Figure 1 operation as standby status display indicator circuit or send only. By when connect at antenna line out of the ham radio transceiver to RF Input.

Figure 1 The Ham radio transceiver status display indicator

In normally status, when we do not push a RTT button (Push to Talk)To send signals D1, D2 no signal through Q1 and Q2, will also be OFF still, LED1 will glow because has positive current through R2 to LED to ground full circuit. The LED2 also go out because connected through Q2 which be OFF so not current flow.

When press a RTT button to send RF signal, then D1 will detect positive signal only. and D2 detect only negative that out of DCV, The negative signal will pass D2 to ground.

But the positive signal range in to drive Q1 and Q2 conduct pin C and E of Q1 Similarly, short-circuit it. Cause voltage between both lead is 0V, LED1 across has voltage drop across as 0V so go out.

The Q2 when ON will drive to LED2 glow up. And when release press key RTT will come back to new the standby status is LED1 glow. But LED2 go out.

How to build it

You do not make a PCB because this circuit is easy and small. So can put all parts into the universal PCB board as Figure 2


Figure 2 the component layout of this project

The components List

Resistors ¼W +5%
R1, R3: 4.7K
R2, R4: 1.5K
D1, D2: 75V 150mA Diodes, 1N4148
Q1, Q2: 45V 100mA NPN Transistor, 2N3904

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  1. Khairul

    Hi. Is this working with transmit and receive frequency 30MHz – 108MHz?

  2. Khairul

    Hi again! after I built the circuit, during transmit its working but on received the signal its not working. Please need guide. I’m using a walkie talkie the frequency between 136MHz – 174MHz.

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