Topband: improve the lightnings charges protect for my equipment 160m

[tzikas tzik]

Hello. I have a amplifier for 160m. 3 days ago a storm strikes my
transmitting area, and two lightnings strikes one of the building wherein i
have install
my vertical antenna's support rope. This building has lightning protect. The
result of these strikes was to cause damage to my amplifier. In particular
all of the output mosfets destroyed. My ground system is a single copper
ground rode, 1,5m length.
Here you can see the antenna tuner:
http://natural-gas.webs.com/antenna-tuner.JPG
I am using for protect against antenna high voltage charges a 2.5mH r.f
choke which is connected between antenna feedpoint and ground system.
But after these results i suppose that it isn't works well. I am looking for
an idea, or a cheap product to improve the lightnings charges protect
for my equipment. Thank you in advance.