Hello all, I'm trying to design a radio transmitter at frequency 4Mhz. I have couple of problems but I will post them each in separate thread. The bigest problem is the Antenna design. At 4Mhz the the half-wavelenght antenna will be 3.75 m, which is not acceptable at all due to space limits, even quarter-wavelenght is not acceptable. The maximum lenght that can be used is 1m which is used with 7.5MHz. I have to use 4Mhz because I have some pre-built circuits to use. Q1) I need some help on how to design a good ( if possible) antenna to use with 4 Mhz that will provide good transmition. Q2) I heared about the loop antennas which are tuned using a capacitor, but I don't know what is thier performance for transmition, and how they are fed and what is the thier impedence. Q3) if I had to switch to 7.5 or 12 Mhz (hupfully not) how can I design and feed the quarter-wavelenght antenna. Please help me by providing me with practical hints, I have read alot alot of books and web pages but I couldn't get the right ansower I'm looking for. Thanx in advance for any help.