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KB2VXA > OLDSET 21.07.09 22:43l 27 Lines 1088 Bytes #999 (0) @ WW
BID : 332_VK2TV
Read: GUEST
Subj: Re: IK0VNQ > hum bucking
Path: IZ3LSV<IK2XDE<DB0RES<ON0AR<HS1LMV<CX2SA<GB7LDI<VK2TV
Sent: 090721/2036Z @:VK2TV.#MNC.NSW.AUS.OC #:332 [Kempsey, QF68JX] $:332_VK2TV
From: KB2VXA@VK2TV.#MNC.NSW.AUS.OC
To : OLDSET@WW
Hi Filippo and all,
Sorry OM, you have your coils confused. You're talking about the
energizing winding which carried the DC + AC ripple power supply current,
the topic has already been covered. Now we're talking about a separate
winding that carried AC which induced a magnetic field of it's own having
equal amplitude and opposite phase of that induced by the main winding,
"bucking" it out.
If you remember how to connect transformer windings to obtain a voltage
unavailable from one alone you're familiar with additive and subtractive
voltages depending on phase. When windings are connected out of phase
they are said to buck each other, a portion of the voltage is bucked out.
The very same principle was used in the design of the speaker, without
the second coil the ripple current would produce a nasty hum, AC current
was used to buck it out hence the name hum bucking coil.
73 de Warren
Station powered by JCP&L atomic energy, operator powered by natural gas.
Message timed by NIST: 20:36 on 2009-Jul-21 GMT
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