i have a transmitter about 150 watt (output an 813 tube 1400vdc) at 1431khz (salonika greece) and the antenna that i'm using is an inverted L antenna (with a less than 5l/16 length ,about 20m vertical segment and 40m horizontal segment). the coupler that i'm using now is l-type . at http://www.geocities.com/tzitzikas_ee/antenna.gif you can see a schematic of my coupler.i am using 3 l/4 length radials and 2 l/8 length radials. the ground system is an copper tube 3m approximate which is burried vertically to tha ground.the distance between transmitter and ground system is about 10m
i would like to improve the efficiency of my antenna. i have 3 thoughts
1) to cut the antenna at l/4 length and to use an 50ohm coupler ( after the variable coil i must add a variable capacitor 0-1500pf with the one point grounded)
2) to use an l/2 horizontal dipole with 50ohm feed line (coaxial RG213 cable) and to use a coupler like one i described above (thought 1)
3) to keep the antenna that i have now.
i dont want to transmit by using the ionosphere cause my transmitter uses a frequency in the band mw, and at the night my frequency is filled by stronger signals. i would like to have a local strong signal.
which of the above antennas i have described is the best???????
thanks