An amplifier is a circuit with specific components working together to take an input signal and produce an increased version of that same signal. There are many different kinds of amplifiers so for the purposes of the HAM radio article, we will stick to talking about the kinds of amplifiers primarily used in HAM radio.
In HAM radio, linear amplifiers are used to increase the output power from a transceiver. You can use an amplifier on any band although they are mostly used on HF bands. Amplifiers are also available for other bands as well.
Linear amplifiers are used for radio because when information is carried in the amplitude or the frequency if you need that same information at a higher power, you would want that change to be linear so that no information would be lost.
The electronic component inside an amplifier that is actually doing the amplifying is called a transistor. The MOSFET transistor is a very popular transistor among solid state devices and has pretty much replaced vacuum tubes. Vacuum tubes did the same thing except they require very high voltages to power and the tubes are very expensive to replace.
Power Amplifiers in HAM Radio
The most power output that HAMS can operate with is 1500W. The rule of HAM radio is to only operate with as little power as needed for transmitting and receiving your desired messages. Just because we can operate with 1500W does that really mean we need to?
A typical HF transceiver has about 100W of power to output. If you use an amplifier to boost your power to 1500W, you will only have a 12dB of signal gain or two S points. Having one S point (an increase of 6dB) signifies a noticeable gain in signal for receivers.
Do you really need an amplifier?
Power amplifiers are expensive. If you’re looking for a clearer signal or a boost in gain, it might be wise to re-evaluate your antenna setup before leaping into an expensive amplifier purchase. It is also important to make sure you are using the correct and a quality feed line.
Every time you double your power output, anyone listening to what you’re transmitting will only hear a 3dB increase in your signal. That doesn’t seem like very much at only ½ an S point.
Not to say that using a power amplifier is bad, but before spending a lot of money and time trying to pick one out, be sure that your antenna system is doing everything it can for your shack. Then adding an amplifier will really put your shack on the map.
Be sure to upgrade your other HAM shack devices after you upgrade your amplifier so you can be sure to know if they will be able to handle the increased power. Increasing the power transmitted also increases radiation coming from the antenna so be sure to keep it far enough away from other people and their homes.
Linear power amplifiers are the types of amplifiers used mostly for radio and that’s because you want to hear the input signal only at a higher power level. The component inside of the circuitry that is responsible for amplification is called a transistor.
A transistor can either be tube type or solid state. Tube type transistors require a lot of power to operate and you have to let them warm up before use. Solid state transistors require less power and you can pretty much turn them on and go.
For HAM radio the most power you can use to transmit is 1500W but you really don’t need that much. Always evaluate your antenna setup to make sure it is functioning at the highest capability before adding in a power amplifier. Amplifying a signal using an inadequate antenna would only be frustrating and not worth the money spent.
When adding a power amplifier into your arsenal, always remember to be safe! As you use more power, more radiation is transmitted to the surrounding areas. Always keep your antenna the correct amount of distance away from family and friends.