Improving the transmitted SDR signal at 27MHz?

Question

Electronics

For a practical acquaintance with SDR, I wanted to implement control of an RC car through XTRX. I figured out what the native control panel sends: it simply turns on / off the 27.2MHz carrier according to a certain pattern for each of the buttons. Began to implement the same patterns on SDR. The first problem I encountered is the minimum carrier frequency of XTRX is 30MHz. I did not manage to transfer the baseband directly. I got out of the situation by tuning the carrier to 32.2MHz and modulating it with a sinusoidal signal with a frequency of 5MHz. I played with different combinations of carrier / signal, from 30/3 to 50/23, did not notice a significant difference. On the oscilloscope, the resulting signal looks equally dumb, with amplitude beats (as I understand it, due to interference with the positive image of the signal). The second problem is the high-frequency antenna, like a wifi whistle.
Questions: is it possible to programmatically improve the signal shape at the antenna output? Will using a long wire as an antenna improve the situation, or not?

Answer 1

I will answer myself:
- the antenna is important, this is a practically established fact.
- the signal shape at the antenna output and the signal shape at the antenna are noticeably different.
- selectivity of the receiver of the machine - none, it reacts to signals in the range of 23 ... 32MHz.