[600MRG] Loading Coil with a Tuning Disc in the center

[J Mcvey]

I have some similar devices that can be found in old BC-375 tuning units.
I wonder about the efficiency of that setup though,
What about the circulating currents that would set up in the disk? Wouldn't that act like a shorted turn?
 

    On Monday, May 7, 2018, 12:22:41 AM EDT, Bart Lee <bart.lee.k6vk at gmail.com> wrote:  
 
 Andy, that was new to me. So,  I asked John Staples (a PhD physicist) who has been licensed since 1957, our California Historical Radio Society tech-guru. He says:
"The disc plate is a common way to tune the inductance of a coil. See the pic of one in one of my broadcast transmitters, where the plate is inserted from the right side and its position is controlled by the motor."

It would seem to be fine-tuning and more continuous on a fixed coil as opposed to switching.  Maybe a roller inductor device also tunes continuously but that would be more complex with an outside contact.
73 de Bart, K6VK ##


-- -- Bart Lee, 
RETIRED Attorney at Law Bar Status Inactive
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www.bartlee.com {This e-mail address is:Bart(dot)Lee(dot)K6VK(at)gmail(dot)com}


On Sun, May 6, 2018 at 4:05 PM, Andy - KU4XR via 600MRG <600mrg at mailman.qth.net> wrote:

Hi all:

I just obtained a Loading Coil from a Gates ATU. The coil has a movable " Disc Plate " inside the coil.
The Coil was mounted with the tuning shaft going through the bottom of the box, and the tunable end was grounded.
Since it has no effect on Inductance when adjusted, can I assume that the disc varied Capacitance when mounted
inside the GATES tuning unit box ? Below are a couple of links to pics of the coil : Thanks for replies :

https://www.dropbox.com/s/ mwi4merqyc1s3lw/Coil_and_ Tuning_Shaft.jpg?dl=0

https://www.dropbox.com/s/ 4vg56781g4tn470/Coil_and_ Inner_Disc.jpg?dl=0

73: Andy - KU4XR
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