>for example, they don't affect rise times that can seriously increase
>dissipation and cause equipment failure. Capacitors and inductors applied to
>the differential circuit CAN cause problems by >affecting rise times.
Not everything is dependent on some tightly defined rise time. I
have a DX Engineering NCC1 phasor box here that had chattering relays
inside whenever I operated on 160 m. with a 300 watt carrier. It had
bypass caps on the DC T/R switching line. I put a pair of small pie
wound chokes in series with the + and return lines at the box's keying
jack and that fixed the problem. Oh sure I could have spent $20 or
$30 on a bunch of material 31 or lower frequency snap on cores and
wrapped a bunch of line turns around each one and solved the problem
that way, but if you know what you are doing, you can effect a much
more elegant solution with a pair of 50 cent chokes. It pays to look
for little chokes at hamfests and pick them up as they have a lot of
uses. Note however, that this example has nothing to do with square
waves in a PDM speed control on a motor which may indeed require a
sharp rise time.
73
Rob
K5UJ
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