![\"\"](\"http:\/\/w0ep.us\/OM\/wp-content\/uploads\/2011\/11\/Scan_Pic0044-700x663.jpg\" "\\"L")
<\/a> The inductor is in series with the signal (the signal passes through it)\u00a0 and the capacitor is situated between the signal line and the common\/ground line.\u00a0 Because higher frequencies have a harder time getting through the inductor, you can tell that this is “low pass” configuration.\u00a0 If the inductor and capacitor traded roles it would be a “high pass” configuration.\u00a0 Generally, in a ham radio application it is better to use “low pass” so that higher harmonics of the operating frequency are discouraged from getting out onto the antenna and radiating to the rest of the world.<\/p>\nIn this diagram, my L-network is like the top one.<\/p>\n
There are two ways to connect it up.\u00a0 One way has the transceiver on the capacitor side of the inductor (A).\u00a0 The other way has the transceiver on other end of the inductor (B).\u00a0 The antenna takes the opposite end from where the transceiver attaches.<\/p>\n
For impedence matching, if you hook it up one way\u00a0 it matches from high to low impedence.\u00a0 The other way matches from low to high impedence.\u00a0 So it works with antennas that are either higher or lower than what my transceiver desires to see.<\/p>\n
The capacitor is a dual-gang air variable with a gearing system.\u00a0 I don’t know where it came from originally, my father gave it to me.\u00a0 The inductor\/coil is a coil of wire that I made from regular house wiring wire.\u00a0 I used a PVC pipe form, wrapped the coil, and glued some nylon rope fibers to it with epoxy to keep it in shape.\u00a0 Then I soldered little wire tabs on every other turn. The idea came from an article in QST<\/a>.\u00a0 I use an alligator clip to select the appropriate turn.\u00a0 I used these same parts\u00a0 plus one other coil on a parallel\/ladder-line tuner in my previous radio shack.\u00a0 But in this situation my feedline is coax.<\/p>\n To find the right tuning I set up my transmitter on low output.\u00a0 Then I try various clip points with the alligator clip while I run the capacitor through it’s range., watching my SWR meter for a dip (matching condition).\u00a0 If I don’t find a useful spot I swap the transmitter and the antenna connections and go through it again.<\/p>\n In this picture my clip is bypassing the coil completely.\u00a0 The capacitor is at nearly-minimum capacitance.\u00a0 The yellow stuff is hot-melt glue.<\/p>\n
![\"\"](\"http:\/\/w0ep.us\/OM\/wp-content\/uploads\/2011\/11\/GEDC0172-700x467.jpg\" "\\"antenna")
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