Topband: FERRITE BEADS
Earl W Cunningham
k6se at juno.com
Fri Dec 19 08:06:26 EST 2003
Dan, W0VD wrote:
"I need to build a good current balun for 80 and 160 meters. Palomar has
43 material that has a .5 inch hole that 9913f coax will fit through.
These beads are 1.12 inches long. How many of these will I need to put
over the coax to make an effective balun?"
With type 43 material (u=850), you'll need enough beads to cover at least
2 feet of coax to be affective at 160m. 30 beads are recommended for
160m. The beads you refer to are Amidon part # FB-43-1020.
If you use type 77 material (u=2000), use enough beads to cover 1 foot of
the coax,. The Amidon part # for type 77 beads is FB-77-1024, which has
an I.D. of 0.5" and a length of 0.825", so it would take about 15 of
Per Amidon, type 77 material is best for amateur radio frequencies from 2
to 30 mHz and type 43 material is best for everything above 30 mHz.
If you buy your beads directly from Amidon (the manufacturer of the
beads), you'll get them for considerably less than from Palomar. The
last time I ordered from Amidon, their phone number was (800) 898-1883.
73, de Earl, K6SE
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