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Trees and AO-40

Regarding trees and AO-40:
On receive, my understanding is that the principle source of reduced performance is from an increased antenna noise temperature (e.g., if the tree filled the entire main beam, the antenna noise temperature would approach 290K).  Combating this effect would require increased G to maintain equivalent receive SNR (specifically, increased G to maintain a constant G/T).
1.	On (S-band) receive, is there also a significant attenuation effect?  In other words, do I need to increase G more than just the increase in T due to antenna noise temperature?  How much?
2.	On transmit, is there a similar transmission loss that is significant?  I would assume U-band TX is largely unaffected by trees, but L-band may be…no experience here.
If it makes a difference, the tree in question is a tropical ‘Tipu’.
All for future station planning…thanks in advance

Scott Townley NX7U
Gilbert, AZ  DM43di

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