[TowerTalk] Common mode choke
jim at audiosystemsgroup.com
Thu Nov 7 13:04:02 EST 2013
On 11/7/2013 8:14 AM, Dan Atchison wrote:
> With my second floor shack, I have common mode RF issues that have
> been well mitigated with common mode chokes of 5 FT240-43 cores, but
> at 40 and below frequencies the choking could be improved. I ordered
> several FT240-31 mix cores and was going to replace the 43 mix, but
> thought I might have good luck if I just added the 31 mix with the 43
> mix, i.e. 10 ferrite cores in a choke as opposed to five. Are there
> any disadvantages to this or perhaps is it overkill?
Nothing wrong with using #31 and #43 together, but the more important
issue is the number of turns. Without winding enough turns, the
resonance is too high be be useful.
More to the point though -- exactly what "common mode issues" are you
having? Perhaps the real issues are equipment with Pin One Problems,
and/or antenna problems. I suggest that you study
http://k9yc.com/RFI-Ham.pdf to first understand the Pin One Problem and
RFI in general, and second for specific suggestions of how to identify
and fix the problems.
73, Jim K9YC
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