I'm on a bit of a retro transmitter trip at the moment. Armed with some low profile 3.6864 crystals I built the "Simplex Sidebander" described in the first volume of Drew Diamond, VK3XU's wonderful "Radio projects for the radio amateur".
The transmitter is simplicity itself. An NE602 with a crystal pulled up in frequency produces double sideband that goes through a 4 crystal bandpass filter. Three RF gain stages produce about 4W out. The final is a low cost IRF510. Mic amp is a 741. Here's how mine looks:
Despite trimming the oscillator crystal I couldn't get decent sounding sideband out of it. The reason is that the little crystal wouldn't pull high enough. Acting on the advice of SmartFriends™I replaced the single crystal, first with two and then three of the little ones and in the end with three larger crystals which seem to pull more. In the end I have a full size polyvaricon for tuning:
Drew warns that the whole thing needs to be in a shielded box and I can attest to the fact that when attached to my antenna it takes off magnificently.
The exciter itself seems very narrow to me - here it is fed into a local SDR.