Singnals, filters and power output

You want a very basic AM transmitter. The old Knight-Kit C100 walkie-talkie has a very simple design. It used a super-regenerative receiver, to minimize parts count. It had one crystal, to set the transmitting frequency, and three transistors. You could probably simplify that, to make just a transmitter. The schematic USED to be available on the Web, but it appears to have vanished.

OLD copies of the Radio Amateur's Handbook should have circuits that could be adapted to a simple transistor AM transmitter.

If I were going to try to throw something together, I'd probably go DSB rather than AM, and use an SA612AN (NE602 replacemement). Instead of a VFO, I'd hang the crystal on the SA612AN, and I'd probably try a plastic 2N2222A, either barefoot or driving a 2N3866. I'm not sure what I'd use for an audio preamp. Here's a more elaborate transceiver, that illustrates the basic principles.

Now for the bad news. There's no way you're going to power this from a CR2032 coin battery. Look at camera batteries, like a Kodak 2CR5 6V lithium battery.

Or will there be some modifications? For example getting triangular a bit?

No, not if the filter is linear. By more or less definition, the output signal from a linear filter does not contain any frequency that isn't present in the input signal.

If the input is a sinusoidal signal and the output is not a sinusoidal signal, even if by just a bit, the filter is not linear since, as Fourier analysis shows, a non-sinusoidal signal necessarily has multiple sinusoidal components of different, related frequencies.

Thus, to make the sinusoid triangular a bit requires adding frequency components that are not present in the input signal, i.e., adding harmonic distortion.

In summary, if the filter is linear, a sinusoidal input of (angular) frequency \$\omega\$ will result in a sinusoidal output of frequency \$\omega \$ with, at most, a modified amplitude and phase.

$$v_I(t) = \cos\omega t $$

$$v_O(t) = |H(\omega)|\cos[\omega t + \phi(\omega)] $$