At 10:07 AM 2/26/99 +0100, Carsten Esch wrote:
>
>Hi,
>
>I build some W6PO 2m linears with the 3CX1500A7 in the past but was
>always wondering on how to decide how many screws (what distance between
>screws) I should use to get the top cover closed (regarding RF).
>What if I use perforated metall for the top cover? What would be the
>'maximum' size for these holes?
>
The general rule of thumb is about 1 every 1.5 inches 0r 4 cm. Hole size is
not all that critical as long as you don't get absurd. Wire fan grills do
not provide any shielding what so ever. The best axiom I ever heard in this
regard is "RF loves seams". With high power RF amps use solid panels. The
only perforated areas should be for air intake and exhaust. Make sure the
cabinet is well ventilated. Use a second Muffin type fan to push area
through the cabinet.
73s
Bob K1TA
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