Total posts : 45366
Bill, I am not sure what setup you are using. If it is a typical base loaded antenna with taps and the transmitter ground is at the base in the earth, I would recommend that the cap be placed at the top of the coil in series with the antenna. If you connect it to the bottom of the coil, the transmitter will be feeding the series LC circuit in the middle and the cap will shunt the RF to ground. I have read articles about this where the cap is in the ground lead. It will do no harm to experiment with either connection and choose the one that works best.
Here, I use a tuning cap in parallel with the loading coil forming a parallel resonant circuit and link to the transmitter with a coil wound around the cold end of the loading coil. ***Edit*** I neglected to mention that the bottom end of my coil is connected to ground.*** I built the coil and antenna for another purpose but it works well on part 15 AM and gives a really sharp peak at resonance. It is so sharp (high Q) that I had to connect a resistor (R 18 in the SSTRAN) to lower the Q so the audio sounds right.
Check this link for some more information.