On 8/11/2014 8:59 AM, Pete Smith N4ZR wrote:
I have an inexpensive Qualtek computer input line filter that is rated
250 VAC at 3 amps.According to the schematic on the side, the third
wire is grounded to the chassis on both sides of the filter. Would
such an arrangement make for better filtering by solving the pin 1
problem, for the device using it?
Yes, it certainly would, Pete, provided that the length of the wiring
between the noisy equipment and the filter was very short. Ideally, such
a filter should be built into the equipment, and there are commercially
available filters with a standard line cord and chassis mount. Again,
though, care must be taken that the connection to the shielding
enclosure is actually made -- the most common failures being paint in
the way, or connectors mounted to a PCB whose shields don't get bonded
to the chassis at the point of entry. Most ham rigs have that issue
with connectors for control lines. Although most screw the RF connectors
down to the chassis, they forget all the rest. The Elecraft outboard
XV-series transverters fail to bond the RF inputs and outputs -- the BNC
connectors are insulated from the chassis, and the two I own (for 2M and
220MHz) have stability issues.
73, Jim K9YC
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