On 6/16/2014 5:36 PM, Howard Lester wrote:
In general, #31 is better for suppression at the lower frequencies
(offhand, I am thinking approximately 80 - 15 meters); #43 is best for the
higher frequencies and VHF. Perhaps Jim Brown will post more precise
information here as to frequency ranges for each.
I've done that. It's in k9yc.com/RFI-Ham.pdf My work is more definitive
than Fair-Rite's, although they did revise their product line and data
sheets based on my work. :)
In general, #31 is the better choice below 5 MHz and quite effective up
to 200 MHz, #43 is slightly better above about 20 MHz, and the two are
equivalent between about 5 MHz and 20 MHz. You can see this by studying
the graphs in my pdf. In all cases, for suppression at HF and MF, you
MUST wind a suitable number of turns to move the resonance to the range
where you need suppression. It's a very low Q resonance (that is, quite
broad), typical circuit Q of about 0.4 - 0.5.
At whatever quantity you're buying #43 is perhaps 10% cheaper than #31.
But the discounts for buying in quantity are much greater than 10%, so
I've always bought #31.
73, Jim K9YC
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