You may hear distant operators in the morning and nobody from the same area in the evening. That does not automatically mean your antenna changed: 27 MHz propagation changes with the ionosphere and solar conditions.
Daily variation
The ionosphere evolves with sunlight. Paths may open during certain hours and close as conditions change. Local terrain and noise still matter, so a quiet receiver is not definitive proof that a long-distance path is closed.
Seasonal and solar influences
Sporadic-E openings can make relatively shorter skip paths active at times, while the larger solar cycle affects the probability of higher-frequency HF openings. Solar disturbances may also block or degrade some paths.
What to do on a busy band
- Listen before calling and identify yourself clearly.
- Try another clear, permitted CB channel if the current channel is full.
- Use a properly matched antenna and legal operating power.
- Keep an ordinary log of observed channels, conditions and contacts.
See solar and skip conditions and NOAA’s resource: NOAA HF radio and space weather.