On 10/11/2011 06:33 AM, Jose Orellana wrote: > > Hi all. > > One question.... > > The typical (20ft) loop to receive (160m) is omnidirectional or need a rotor > ???? > > I have seen many have fixed and others have a rotor.
The main reason a receive loop is quieter than a vertical is that it blocks out noise from other directions. It does this by being directional. An unterminated loop has two narrow nulls off the sides, in other words it is not very directional and only a little lower noise than a typical transmit antenna. Then there are terminated loops, like the K9AY or the flag antenna. These only "see" the signal from one direction, with good attenuation in all the other directions. By reducing signal from more directions, they are lower noise than unterminated loops or omnidirectional antennas. If you are going to build a receive loop and are willing to get a rotator (or a set of two loops and relays), you might as well go for the terminated loop variant. A rotatable flag would work, as would a switchable set of K9AY loops. Which leads to my own question on this topic: Is it possible to build large flag antennas that are at 90 degree angles, like in the K9AY array? I know that switchable direction flag antennas are being built, if I can just build two of them I'll have a ground-independent antenna much like the K9AY array (but with about 10dB more signal). -- All rights reversed. _______________________________________________ UR RST IS ... ... ..9 QSB QSB - hw? BK
