Hi
i have a doubt
i have many towers install at many small city/villages on which we install RB411/433 and r52 card with sector antenna
all the tower are properly grounded but i am afraid if i attach the board’s ground to the tower it will solve the grounding issue but in case of heavy lightning it may make the board dead
NOTE: we are using gas lightning arrestor between the radio card and the antenna and that is grounded
so is it safe??
If the Tower is grounded, ground all Your Equipment. If the Tower is not grounded, dont ground eqipment. Also think about the grond from Power from electrical Company.
We grounded some of Our Tower, and have never had so much troble when Thunder was coming. Removed all grounding, and all was ok. Think about it. Thunder storm is some km away, but grond cable transfer electical Power to Your eqipment. Going stright into the Cards in radio.
Try as far as possible, to dont have any Connection between Tower and Equipment, and use doble isolated Powers etc.
But if there is grounded. Try to ground properly. Grond ground ground, and gronud even more. Also get som Power With gronding, and use a Ethernet cable that is grounded/shielded.
Btw, some may not agree to this, and this is a really big sience, and may be the root of really big discussion. 
Gronding is the only defence against EMP etc. (if u are afraid of this)