RadioRon
Well-Known Member
CSXCONDUCTOR said:
Usually the ferrite rod windings are tapped a little ways in from one end. This tap wire is where you hook up you radio input if you want to make a wire connection. The ground side of the radio connection would go to the end of the ferrite winding nearest the tap. You would connect the 365 pF variable capacitor across from the remaining ferrite wire connection (the end we haven't used yet) to that ground connection, or in other words, across the entire coil.
It isn't absolutely necessary to make a wire connection to the radio as you can get most of the benefit of the booster antenna just by bringing it near the AM antenna that is already in the radio. They connect via magnetic field coupling. In this case, you just connect the capacitor across the ferrite windings and thats it, but be sure to line up the ferrite rod with the one that is inside the radio and put their ends close together.
I've had a lot success building large wire loop antennas that don't use a ferrite bar. The problem with these however is that they are large. One example that worked well with a 365 pF cap was wound on a square piece of cardboard, about 18 inches on a side and if I recall correctly, it took about 12 to 15 windings. You have to experiment with the number of windings to get frequencies you want. The larger the area of the coil, the better. Its pretty obvious when it works as you just put it near your AM radio then adjust the variable cap, and you will hear the volume of a weak station suddenly increase dramatically when the antenna resonates. This kind of antenna is good for many tens of dB worth of extra signal, the improvement is really exciting!
