On 3/5/2013 11:57 AM, N1BUG wrote:
I suggested he invest in a good number of ferrite cores to place on
the cables.
We are a small club with limited funds, but at some point I hope we
can invest in a good quantity of several of the more useful RFI
suppression cores to have in a RFI "go kit". That way we can try them
in various RFI situations to see if that is the answer. If they work,
we can leave them in place and have the recipient reimburse the club
for the cost of replacing the cores in our kit. I like this idea
better than suggesting folks go out and buy these things, particularly
for VHF cases where this approach may or may not succeed.
Yes. The principal objective of the ferrite research that I began around
2002 was to identify a few part numbers that could be bought in quantity
and used to solve a broad range of RFI issues. The part numbers I
identified are in Appendix One of my tutorial. Although I studied a half
dozen Fair-Rite mixes, I soon zeroed in on #31 because it was optimum
for the lower HF bands and AM broadcast, and nearly as good as #43 into
the VHF range. And although #43 is a bit less expensive for comparable
quantities, I realized that #31 would be cheaper if if we can buy higher
quantities,. and that we could do that if we didn't split those
quantities between different materials.
The key to quantity for these parts is a group purchase, and the key to
that is to collect orders from more than one club. I've arranged several
myself, and helped others do so as well. If I were trying to organize
one in your area, I would talk to DX and contesting clubs like YCCC,
FRC, PVRC. These are big clubs with members spread over a pretty wide
area (the ARRL contesting circle has a 175 mile radius, and the club can
place its center as it likes, usually to maximize the club score. I'd be
willing to bet that all three of these clubs have done at least one
group purchase of ferrite cores.
There are some general guidelines -- Fair Rite sells direct ONLY in full
box quantities and there are minimums that vary with the size and cost
of the part. They are very good to deal with direct, and they will drop
ship to multiple destinations (again, full boxes only). Full boxes are
good, because ferrites are fragile, and I've seen breakage in shipments
that were not full boxes (but never in a full box packed by Fair-Rite).
I also suggest that for these reasons, you ship full boxes to locations
in each city, where a member will distribute them by hand at club meetings.
So check out Appendix One of my tutorial. It also includes a worksheet
to help hams figure out how many of various parts to buy. The worksheet
is geared toward HF operators, so you might want to modify it for
VHF/UHF work.
http://audiosystemsgroup.com/RFI-Ham.pdf
73, Jim K9YC
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