locked Re: Hamlib 4.5 testing #hamlib


Jim Brown
 

On 8/9/2022 9:45 PM, Tim Dawson wrote:
It's in a solid metal case -*THAT* is far better shielded than plastic or nothing
Not necessarily. Properly laid-out circuit boards using microstrip (traces above a CONTINUOUS "ground" layer) form transmission lines with that layer confines signal return current to the ground layer immediately under the trace, making the circuitry self-shielding. Stripline, (sandwiching the signal layer between a pair of "ground" layers) provides significantly greater shielding. These types of construction are necessary to prevent crosstalk between circuits.

Proper layout is the key -- the ground layer must not be interrupted under a trace, because it's no longer a transmission line.

. . . (there is far more to shielding than just the cable!)

YES. And for cable shielding to work, it must be bonded to the shielding enclosure AT BOTH ENDS, AT THE POINT OF ENTRY. If there's no shielding enclosure, it must be bonded to the ground layer of that microstrip or stripline board.

73, Jim K9YC

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