wrote:
Hello. I have designed an antenna with the 4nec2 program.
It is a 698 MHz Bow Tie antenna. The simulations confirm excellent results:

- Impedance 75 Ohm
- SWR 1:05
- Gain 10 dBi.

Really building the antenna, it doesn't work, even though I have retuned the TV. The signal is 0.

On the other hand, by building a dipole tuned to 698 MHz (half wave) the TV works perfectly.

Can you please tell me why?

Probably there is no TV on 698 MHz anymore (or it is going to be shut
down soon). Check the frequency of the transmission.

Of course that would not be the reason for 0 signal but it will not
perform optimally. For 0 signal check for connection faults.