By adding an antenna tuner to the equation, what you’ve done is make it possible for the radio to put as much power into the feed line as it can. The key point to keep in mind is that the SWR reduction only occurs between the antenna tuner and the radio. Now you know why many hams prefer open-wire feed lines, but that’s a topic for another time. On the other hand, if your feed line is something like open-wire line, the loss will be minimal regardless of the SWR.
If you’re using coaxial cable and operating on one of the higher HF bands, such as 10 meters, this loss can become serious if the SWR is high. How much is lost due to SWR depends on the type of feed line you are using and the frequency at which you’re operating. Having an elevated SWR between the antenna and the antenna tuner can result in some portion of your power being lost as heat. It’s from the antenna tuner to the radio where the SWR will be 1 to 1, or something close to it. Many hams don't realize this, but when an antenna tuner achieves a low SWR for your transceiver, the SWR between the antenna tuner and the antenna is unchanged.įor example, if you have a 2.5 to 1 SWR between the antenna tuner and the antenna, the SWR in that portion of the feed line - let’s say it is your coaxial cable - will remain at 2.5 to 1. Seems simple, doesn’t it? But as you can imagine, there is a catch - and it’s a significant catch. The result is a 1:1 SWR, and your transceiver is happy to dump its power into the circuit. By using different amounts of inductance and capacitance, the antenna tuner can convert the antenna system impedance to 50 ohms for the radio. That’s where the antenna tuner comes to the rescue. So, if you want to load all your available power into the antenna system, you need to get the SWR at the transceiver below 1.5:1. It sounds complicated, but all the circuit does is reduce the radio’s output whenever it detects that the SWR has exceeded about 1.5:1. Transceiver manufacturers try to protect your radio from damage by including something called a foldback circuit. Suffice to say that an elevated SWR can be problematic for your radio.Īn elevated SWR can cause high voltages to appear in your transceiver’s output circuitry, and this is never a good thing. We explain SWR in the January/February 2021 issue (see “Untangling SWR”), so I won’t get into it here. If the antenna system impedance deviates too far from 50 ohms, the result is an elevated standing wave ratio, or SWR, at the radio.
So instead, manufacturers design radios to deal with 50-ohm impedances at their outputs. They certainly could be more flexible, but that would add substantial cost - and physical size - to the radio. What’s the point of doing that? Well, modern transceivers are only designed to handle a narrow range of antenna impedances. When you reduce the function of an antenna tuner to the bare minimum, it’s as simple as this: It matches the impedance of the antenna system - measured in ohms - to the impedance the transceiver needs to see, which is 50 ohms.
#Antenna tuner simulator how to
In the January/February 2021 issue of On the Air, we spent several pages talking about antenna tuners, in the articles “Two Types of Antenna Tuner,” “Untangling SWR,” and “Antenna Tuners: Making a Match.” Here’s a closer look at how they work, how to buy one, and other considerations. By Steve Ford, WB8IMY, ARRL Contributing Editor
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