I (so far) use ferrite cores only for common mode chokes and I've made
and used many particularly for 160. 75, and 40 center fed slopimg
dipoles and half slopers.
73, Roger (K8RI)
On 7/16/2019 12:34 PM, Rob Atkinson wrote:
Many hams blow money on ferrite needlessly, because they see it as
this magic bandaid bullet for all their RFI problems, whereas an
understanding of RF and DC will lead them to much less costly
solutions in a number of cases:
RF on low current DC supply lines: Inexpensive small pie wound chokes
which can be found for small change at hamfests can be put in series
with power supply lines to small appliances at the enclosure to keep
RF out of shack accessories.
RF audio or relay coil lines can be cured with inexpensive small 0.1
or .01 ceramic bypass caps to ground.
Audio isolation transformers can be strategically placed to block RF,
ditto for AC mains isolation transformers which can be found at
hamfests for a few dollars to be placed ahead of switching supplies or
other direct rectification supplies.
Opening the shield on multi-conductor lines with it at ground on the
opposite end can keep RF on the outer surface of the shield from being
conducted to the affected device.
Ferrite has its uses but should be a last resort. But I see hams
spending hundreds and hundreds of dollars on the stuff and trying to
solve every sort of problem with brute force of ferrite which makes
vendors happy but may be a waste of money.
73
Rob
K5UJ
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Roger (K8RI)
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