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?