The theory, design and construction of antenna tuners is a very technical subject that is beyond the capability of this website, so I have chosen to provide articles and examples that might be of use to hams.  These concern manual tuners and not automated units or those built into a transceiver.

Antenna Tuners do not tune your antenna.  Their job is to match the impedance of your antenna system to the impedance of your transmitter.  Think of them as a transformer designed for RF frequencies.

Some prefer automated antenna tuners; we will not address them here.  Instead we discuss manual tuners that are easy to build.  A disadvantage of these, compared to automated tuners, is that they must be manually retuned with each significant shift in frequency.  However, this can be largely overcome by keeping a spreadsheet of settings for each frequency in common use.  The dials can be rapidly moved to these settings when needed.  Just remember to not “hot switch”  (switching it while transmitting) the tuner’s coil, which can damage the switch’s contacts.

Remember that a perfect 1:1 SWR is not necessary.  Most modern solid-state transceivers will work into as much as a 2:1 mismatch; perhaps with some reduction in power.  Tube and Pi network finals can often work into higher mismatches than this.

Perhaps the best book to read on this subject is The ARRL Guide to Antenna Tuners.  Everything needed is explained in this publication.

Here is a quick overview of different types of antenna tuner circuits and their advantages and disadvantages.

Here is a second article about the different types of antenna tuner circuits, their advantages and disadvantages.

Perhaps the most common design is the “T-Network,” and AA5TB illustrates the schematic of such a network and has good photos of the one he built from surplus parts.

The T-Network illustrated in the AA5TB article will match unbalanced (coax) line systems, but if a 1:1 balun is placed between it and a balanced line (i.e., Twinlead), it can be used to match a twinlead fed system as well.

Using a balun in this manner will work with Pi and L type tuners as well.  Want to learn about baluns?  Go here for this information.

AD5GG has published an informative article on Antenna Tuners, Impedance Matching and SWR.  It’s a good read and the article contains links to other information sources.

K6JCA has published an extensive article on L-network antenna tuners.  It is rather technical but very informative.  He points out that there are eight different variations of L-networks, and they are explained by this article.

Have your Pi and your L and your T, too?  This article provides a way to put them all in one box.  I won’t build one of these since my homebrew Pi and L tuners tune any antenna I have yet tried.  Maybe I’ll build a junk box T tuner, just to have all three types.