[600MRG] s/c inductor tuning loops

[sbjohnston at aol.com]

The RCA BTA-5T 5kW broadcast transmitter used a metal cylinder on a threaded rod inside a PA tank coil.  A motor drove it in and out to tune.  

You can see it in the top left corner of the transmitter rear view image which is the top left photo on this page:

 
http://www.broadcastdocuments.com/BROADCAST_DOCUMENTS/BTA-5T1.html



Steve WD8DAS

sbjohnston at aol.com
http://www.wd8das.net/
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-----Original Message-----
From: Rudy Severns <n6lf at epud.net>
To: 600MRG <600mrg at mailman.qth.net>
Sent: Tue, May 8, 2018 6:13 pm
Subject: [600MRG] s/c inductor tuning loops



Hello All,
 
Over the past few days there’s been some discussion of floating short circuited loops or metal discs placed inside a coil to adjust the inductance.  The idea absolutely works but it’s a disaster for the coil Q.  To illustrate the problem I ran a quick experiment to illustrate the problem.  I’ve written a short note on the work which is posted at: www.antennasbyn6lf.com .  In due course I’ll expanded this to give a detailed explanation of the phenomena and show a similar but not nearly as serious effect in variometers but this will have to do for right now.
 
GL and 73, Rudy n6LF

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