Inverted L Antenna

 I will describe a very good antenna for 160 meters, the Inverted L.

The inverted L comes in many configurations, some better than others. The Inverted L that I use is not a new antenna, on the contrary, it was described to me many years ago by a man called Mr. 160 meters, W1BB. 

An inverted L is simply a top loaded vertical. Since it’s is nearly impossible to get a horizontal antenna high (in terms of wavelength ) on 160 meters it is necessary to use a vertical radiator to get low angle radiation. A quarter wave vertical with a extensive radial system has been a good 160 meter antenna. However it has some limitations. First of all a 130 foot vertical is not easy to install and it has the maximum current point right at the base or ground. It is always best to have the high current point higher above the ground.  The inverted L has a vertical portion somewhat less than a quarter wavelength, maybe 40 to 65 feet. It could be somewhat more or even less if necessary. The rest of the antenna is bent over at the top and runs horizontal to provide top loading for the shorter vertical portion. The usual Inverted L is simply a total of 1/4 wave long and when used with a ground rod or radial system it can be fed directly with coax. This still has the high current point at the ground or feed point. The input impedance at resonance will be the sum of the radiation resistance of the quarter wave vertical ( 36 ohms resistive ) plus the ground loss resistance. In general this totals close enough to 50 ohms to be a good match for the 50 ohm coax. However on 160 meters this setup will not have a wide bandwidth between the 2:1 SWR points. If the total length of the antenna is increased over a quarter wave to somewhere near 180 feet, the current maximum will move up from the feed point and the Real Resistance will increase to more near 50 ohms. Both of these things are good and will improve efficiency. If fed against the same ground as a quarter wave inverted L the impedance will be inductive and the efficiency will be higher. A simple series capacitor can then be used to tune out the inductive reactance. Since the real R value will not change much across the band, simply resonating the antenna with the capacitor anywhere in the band should give a good low SWR.

My inverted L is 60 foot vertical and 119 foot horizontal. I have used this antenna to work over 100 countries on 160 meters. The vertical has gone from 40 to 60 feet over the years with the horizontal portion going from about 125 to the present 119 feet. For a ground system even a single ground rod can work but I mostly use two or three radials. Obviously more radials are better. For me the first two make the most improvement with diminishing returns after that. This antenna is definitely better than any horizontal antenna I could put up on 160 meters for DX and probably just as good for high angle work. I can almost always work 400 to 700 QSOs in the 160 contests with this antenna. 

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