At 100.0 degrees Fahrenheit the temperature sensor will have an output of a value related to Celsius, so to make life easier, we will convert to Celsius first. So:

C = 5/9(F-32) or C = 5/9(100—32) which is 37.78 degrees Celsius.

This means the output of the sensor should be 377.8mV at 100.0 F.

So to convert 377.8mV to 1.965 volts we need to multiply by:

1.965 / 0.3778 or 5.201. This will be the gain we need from the non-inverting amplifier.

We go back to our old non-inverting amplifier formula of:

A = 1 + Rf / Ri, which is the gain of the non-inverting opamp.

We already have Ri = 1.00K and A of 5.201 so we have to find Rf.

Rearranging we get Rf = (A-1) * Ri so Rf = (5.201—1) * 1000

So Rf = 4.201K. Our closest 1% value is 4.22K.

Binary math

Oh no! Your brain hurts and doesn’t want any more theory; on to the kit building! Ok, go ahead and build the kit, but come back here later to review how to read the display properly, and why it works that way.

Normally we would only deal with integer binary math, but we at Ramsey like to mix things up a bit, and throw in fractional binary math so you learn something new! It is the basis of how all math works on computers, including that pesky floating point stuff, especially on DSPs. We will also learn why computers are NOT perfectly accurate.

A binary number is either 1 or 0, on or off, meaning it is only two states. Two LEDs will have 4 potential states, 3 will have 8 states, and 4 will have 16. The relationship is 2 to the power of the number of bits. This is seen as 2^n when n is the number of bits. In the case of our display we have 8 bits, so we have 2^8 or 256 potential states.

As the value counts up, you will see the right most bit (LED) toggle the fastest. This LED is considered the least significant bit, meaning it has the least value associated with it. In our case it is worth a measly 0.5, but normally would be worth 1 if we didn’t throw in a decimal point to confuse you. The LED on the far left is called the most significant bit, because it is worth the most. In our case it is worth 64 but normally 128. This is because the .5 LED had to flash

CT255 • 10

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Ramsey Electronics CT255 manual Binary math
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CT255 specifications

The Ramsey Electronics CT255 is a versatile and advanced communication tool designed for radio enthusiasts and professionals alike. As a 2-meter FM transceiver, it is known for its robust performance and extensive feature set, making it ideal for both casual users and serious operators.

One of the standout features of the CT255 is its compact design, allowing for easy integration into various environments such as home stations or portable setups. The unit is built with user-friendliness in mind, featuring an intuitive interface with a clear display and easily accessible controls. This ensures that users can quickly tune into their desired frequencies and modify settings without extensive technical knowledge.

The CT255 operates on a frequency range from 144 to 148 MHz, providing access to the popular 2-meter amateur radio band. This frequency capability is complemented by an impressive output power of up to 25 watts, ensuring robust communication over extended distances. It also includes a built-in automatic repeater shift, which simplifies contacts through repeaters, making it an excellent choice for those looking to enhance their communication range.

In terms of technology, the CT255 employs advanced digital signal processing (DSP), which significantly improves audio clarity and reduces background noise. This makes communication clearer, even in less-than-ideal conditions. Additionally, the transceiver features an array of scanning functions, including memory scan and priority scan, allowing users to monitor multiple channels effortlessly.

The CT255 comes equipped with multiple memory channels, enabling easy access to frequently used frequencies. This feature is particularly useful for users who participate in various nets or have multiple repeaters they commonly contact. Moreover, the unit supports CTCSS and DCS tones, which adds an extra layer of privacy and reduces interference from unwanted transmissions.

Safety and durability are also key characteristics of the CT255. The robust construction ensures it can withstand the rigors of regular use, making it suitable for field operations. It is designed with heat dissipation features to prevent overheating during prolonged use, ensuring reliability during critical communications.

In conclusion, the Ramsey Electronics CT255 is a well-rounded transceiver that brings together advanced technology, user-centric design, and excellent performance. Its range of features makes it an appealing choice for radio amateurs seeking a dependable and efficient communication solution. Whether for casual chatting or emergency communications, the CT255 stands out as a reliable tool that meets the demands of modern radio users.
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