1750Hz tone generator
The 1750Hz tone bursts are often used to trigger repeaters. There are several methods to build 1750Hz tone generators which including TC5082 divider, using MCUs, etc. In this post, I present another 1750Hz tone generator which I built using 74HC4060 high-speed 14-stage binary ripple counter and 7.168MHz crystal. In this design, 74HC4060 is used to drive the crystal and divide its output by 4096. By using 7.168MHz crystal, this circuit produces 1750.0Hz square wave output with a 50% duty cycle.
This circuit is extremely simple to build, and I construct my prototype using a breadboard. I tested this generator by connecting its output to my Baofeng UV-5R handheld transceiver and it gives an excellent result. The key motivation to build this generator using 74HC4060 is, because of its common availability. Most of the tone generators which I found on the internet are built using MCUs or by using rare ICs, because of that reason most of those circuits are quite hard to assemble and test. In this design, the only component which is difficult to find is 7.168MHz crystal. I purchased a few of those crystals from the local market, but at the time of this writing, this crystal is available to order at Mouser electronics and a couple of other distributors.
If targeting repeater accepts 5Hz to 8Hz offset, then this circuit can be built using generally available 7.2MHz crystal. With 7.2MHz crystal, the generator produces nearly 1755Hz to 1780Hz output.
