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KB2VXA > OLDSET 23.07.09 05:08l 27 Lines 1105 Bytes #999 (0) @ WW
BID : 386_VK2TV
Read: GUEST
Subj: Re: G4UEQ > hum bucking
Path: IZ3LSV<IK2XDE<DB0RES<WA7V<KD4YAL<VK2TV
Sent: 090723/0248Z @:VK2TV.#MNC.NSW.AUS.OC #:386 [Kempsey, QF68JX] $:386_VK2TV
From: KB2VXA@VK2TV.#MNC.NSW.AUS.OC
To : OLDSET@WW
Hi Terry and all,
It's becoming clear, I had my suspicions that the coil derived current
from the heater (A) supply and putting it in series with the string makes
sense, a current limiter. Now to speculate on the reason for the
electrodynamic speaker in the first place, having seen a few PM speakers
from that era they were pretty crappy affairs. Before alnico magnets they
were soft steel and went dead rather quickly like those in old telephones
where the hand crank ring generator had to be replaced after a while.
I had a couple of old PM speakers of the moving magnet type, strange
affairs with a horseshoe biasing magnet having coils on the pole piece
assemblies and a magnet mounted on a stud where the voice coil normally
is. They sounded nasty, low volume (weak magnets) and those stiff edged
cones didn't help, something like the old tulip horn record players or a
tin can telephone, yuch.
73 de Warren
Station powered by JCP&L atomic energy, operator powered by natural gas.
Message timed by NIST: 02:48 on 2009-Jul-23 GMT
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