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IZ3LSV

[San Dona' di P. JN]

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KB2VXA > OLDSET   23.07.09 04:08l 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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