lightning arrester @ base station

[foTONICS]

Hello all,

We were having a discussion about lightning arresters at radio towers and their purpose (providing lightning a easier path to ground so as to not destroy the sensitive Rx). But someone brought up a good point, what stops the wanted RF signal from being shorted to ground? He mentioned that the RF signal, or the lightning arrester (can't remember which one) was capacitively coupled into the network.

1: Would I be right assuming that the cap blocks the lightning since it's DC?

2: Since signals like the easiest path to ground why would the RF signal choose to go through the capacitive network, through the Rx, and all those cable connectors and attenuators instead of just choosing to go to the ground spike at the back of the shed?

 

[KJ6EAD]

A lightning arrestor is made with a gas discharge tube. The low voltage of the RF signal isn't nearly enough to ionize the gas, providing a path to ground. Lightning easily ionizes the gas.

 

[davenn]

Hello all,

We were having a discussion about lightning arresters at radio towers and their purpose (providing lightning a easier path to ground so as to not destroy the sensitive Rx). But someone brought up a good point, what stops the wanted RF signal from being shorted to ground? He mentioned that the RF signal, or the lightning arrester (can't remember which one) was capacitively coupled into the network.

Neither .... As the other responder commented gaseous arrestor are commonly used.
The other common method is non gaseous spark gaps

1: Would I be right assuming that the cap blocks the lightning since it's DC?

No lightning isn't a DC voltage discharge. It comes from a high build up of a static charge

2: Since signals like the easiest path to ground why would the RF signal choose to go through the capacitive network, through the Rx, and all those cable connectors and attenuators instead of just choosing to go to the ground spike at the back of the shed?

As already said. The low RF voltage, up to a few 1000 volts or so in a hi power transmitter doesn't jump the spark gap, but the millions of volts in the lightning strike will easily jump the gap

Dave