Hello!
I would like to make an easy roger beep circuit for a 4 pin CB microphone. I want to make it sound like the Quindar beep that the Apollo missions used. In doing research, the Quindar beep used a 2475Hz tone that lasted for 250ms when the PTT was released. See here for more information: https://en.wikipedia.org/wiki/Quindar_tones.
Does anyone know of a good way to approach this project? I'm not really sure how to connect everything up, like the PTT line and such.
How can a microphone make sounds?
By your link, there is one tone to initiate transmission and one to end transmission. I am sure Google can find an oscillator circuit to generate the tone you want. Your research will have to find how to monitor some PTT circiut and find how to delay that on or off while introducing the desired tone into the audio circuit.
I should also add that this is the mic circuit I am working with...it's pretty rudimentary. I'd only like a roger beep on the end of the message, though now that I think about it, it might be cool to add on the initiate tone...
Hello owengman
Welcome back.
Take a search engine of your choice and ask the WWW for 'roger beep +ne555' to collect some data to be sorted out to get the needed information.
So I think I've narrowed down some possibilities...
@paulpaulson, it looks like a roger beep can be made by combining monostable and astable 555 circuits together, where the monostable triggers the on and off of the astable. Please correct me if I'm wrong!
I've also been looking into the ATTiny chips too, as they have a low pin count.
Using 555s sounds good for the tone generators. There is a problem with the 555 one shot. It triggers only on falling edge and the trigger pulse must be shorter than the timing pulse. Pressing the PTT switch can trigger the 555 but you need to shorten the trigger pulse using a capacitor to input that pulse.
I suspect you folks have never heard a NE555 tone over a radio. It will tear your ear drums!
Good point...I'd like it to be gentle on the ears and not annoying and shrill to the point I make anyone deaf 
Perhaps a resistor on the output would help?
Well, of course, since it is to modulate a radio transmitter, we should not overmodulate. The tone probably should not be at 100% modulation. A voltage divider and/or a low-pass filter should be included if the final design.
Oh, and for the tone, it may be better to take the lower amplitude more triangular waveform off the timing capacitor than the pin 3 output.
Thank you all so much - seems like a good place to start! Would someone happen to have a schematic or a rough idea of what the part layouts would look like?
Hi, I wanted to know in detail how to set up the programming via Arduino IDE & Arduino Nano of a Roger Beep for my CB radio, I can't understand, how can it be done?
This topic discusses the electronics, not programming.
Well I might have a solution...
Basically, how this and most other 4 pin CBs work, is that when RX is pulled low (shorted to GND), the radio goes into receive mode. Then when the TX pin is pulled low, it goes into transmit.
There needs to be a board that reads when TX is activated, keep the PTT button pressed for a short time (no more than 300ish ms), and when the beep is sent, return the radio back to RX mode. It sounds complicated, but here's what I'm thinking:
We need 2 inputs - one for the TX pin and one for the RX pin. These need to read the voltage levels on those pins and feed that information to the microcontroller. We then need 2 outputs - the roger beep audio output and another that feeds into the base of an NPN transistor. The collector of the NPN would connect to the TX pin and the emitter to the GND pin. The Arduino will send a signal to hold PTT for the allocated time, send the roger beep via tone() (fed into a resistor for audio limiting!), and unkey the microphone.
Hopefully that makes sense. If not, here is another way of explaining it:
"All that is required of the board is to wake up on a Push To Talk (PTT) switch interrupt (when TX is shorted to GND) and hold down the PTT line to the radio. Once the microphone PTT switch is released (RX is shorted to GND), generate the beep, release radio PTT and go back to sleep."
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