(meteorobs) question about electronics

[Julian Portik]

Hello,

next weekt, I'm going to observe the Orionids with my frame antenna.
Last time I had some meteor related signals, but I'm not sure about it.
Now, I've got something to pull up the antenna one meter above ground
and I hope this will take effect. But there's one question left:
How big should the input resistance be? Is it better to take a tube 
(pentode)
or a FET? So far I'm using an operational amplifier (LM358).
Can anybody give me some advice?

Many greetings

Julian Portik