A Closer Look At Radio Receiver Design
When you first think about designing a radio receiver you may think it is a complicated process based on what you are trying to accomplish. However, the design is actually fairly simple depending on the type of receiver you are trying to make. You can choose to make a crystal radio, direct amplification, reflectional, regenerative, FM, AM, tuned radio, and superheterodyne receivers. Each of the different types has advantages and disadvantages that come along with the design. Most of these designs listed above will be discussed throughout this article to give you a better idea of how they are designed. The most basic and easiest to design is the crystal radio. To design this radio receiver you will need an antenna, cat's whisker detector, variable inductor, and a capacitor. The main advantage of this receiver is its ease of creating it because of the simple components. This is the most popular type of receiver to be made by hobbyist for this very reason. The disadvantages are that it needs a very strong RF signal in order for it to operate correctly, and they normally only have one tuned circuit. These two flaws are limiting, but the design works nonetheless.
Another type of radio receiver you can design is a reflectional one. This type of receiver has a single amplifier within it that is used to amplify the radio first, and after detection it amplifies the sound frequency. Though these are small, simple, and consume a very low amount of power, they are not very stable when compared to the other receivers available. Direct amplification radio receiver designs consist of a radio resonance filter, two-stage RF amplifier, sound frequency amplifier, and a diode detector. This method is also very simple, and was favored by many during the early 1960's by many radio amateurs. Unlike the reflectional receiver, this type consumes a lot of power making it less appealing. The sensitivity could be better, but this design is stable as well as reliable regardless. If you are looking for a receiver that has the potential to be very sensitive, then you may want to look into the regenerative circuit radio receiver. By using positive feedback, this receiver is able to drastically increase the gain of the stage. The downfall to using this type of radio receiver is that it can easily cause radio interference when not used correctly. Avoiding the interference is fairly easy, but there are not many people that are drawn to this design. Direct conversion receivers are designed to filter the aerial signals with a band pass filter, and then amplify them before they reach the non-linear mixer. Once the signal makes it to the mixer, it is mixed with another signal from a local oscillator. When the mixing is completed it is sent through another filter known as the low pass filter before it reaches the audio amplifier. The audio amplifier is the last stage of this process, and the end result is the output to your radio. As you can see from this article, there are many designs that you should consider when dealing with radio receivers. In the end, it really comes down to what you are using the receiver for, and how advanced your knowledge of the design is. No matter what, they all have positive and negative attributes. Before dealing with any radio receiver you should make sure you are up to the challenge before hand. If you fail to do this you could find yourself in a situation where you are unsure of how to get it to work. If that is the case, you may want to consider using a different type of radio receiver that better fits your abilities. |
