Schottky for surge & polarity protection?

[kevj]

Outstanding. Thank you very much Brian - exactly what I was looking for.

[Ioannis]

Have a look at the file I attached. I think it is exactly what you want.

Ioannis

[languer]

Transorbs (like SMBJ) and other TVS (transient volt suppressors) are great for transients. In fact, for lightning protection and such TVS devices are used widely (these are what you find in your surge protection power strips). Schottky diodes would never whidstand lightning transients (and live to see another day).

But schottly diodes have very little capacitance, transorbs generally have a great deal of capacitance. So if you hang a transorb directly across the antenna input, you may as well not worry about reception / transmission (since you will have none).

In your case, a schottky diode in an anti-parallel configuration (as was suggested) maybe all you need. Should you require to add the TVS (there are some very good bidrectional ones - look up AVX's TVS) to the antenna line, you will want to have an RF choke (RF inductor) in series with the TVS. The choke connects between the antenna line and TVS, and the TVS betweeb the choke and power rail (GND most likely). Lookup the following appnotes, they have very good info:
What is a Silicon TVS and How Does it Work?
Selecting the Optimum Transient Voltage Suppressor