Quick Answer
Humidity affects your ham radio's performance by increasing signal loss and distortion, especially on VHF and UHF frequencies, due to water molecules in the air absorbing and scattering the radio waves.
Radio Wave Absorption
Humidity plays a significant role in the absorption of radio waves, particularly in the VHF and UHF frequency range. Water molecules in the air absorb the energy from the radio waves, causing signal loss and attenuation. This absorption occurs more readily at higher frequencies, which is why VHF and UHF signals are more affected by humidity. In general, signal loss increases by 1-2 dB for every 10% increase in humidity. For example, a 50% relative humidity increase can cause a 5-10 dB signal loss, making it more difficult to maintain a clear connection.
Antenna Performance
High humidity also affects antenna performance, particularly when it comes to antenna efficiency and radiation patterns. Moisture can accumulate on the antenna surface, reducing its effectiveness and creating a ‘wet’ antenna that can lead to signal loss and distortion. In extreme cases, excessive moisture can even cause the antenna to become conductive, leading to unwanted signal reflections and noise. To mitigate this issue, use a waterproof or water-resistant antenna, and consider applying a thin layer of antenna coating or sealant to protect against moisture ingress.
Transmission Line Considerations
When dealing with high humidity, it’s essential to consider the transmission lines connecting your ham radio to the antenna. Moisture can penetrate the transmission lines, causing signal loss and corrosion. Use shielded transmission lines with a high-quality, moisture-resistant insulation to minimize signal loss and ensure reliable connections. Additionally, ensure that all connectors and joints are properly sealed and secured to prevent moisture ingress.
Find more answers
Browse the full Q&A library by topic, or jump back to the topic this question belongs to.