[600MRG] Extra Turns - Open or Shorted or Removed

[Edward R Cole]

My base loading coil end is floating with antenna connected to tap:
http://www.kl7uw.com/Coil003_1.jpg

No HV issues experienced driving with 100w into the coil base about 
2-1/2 turns above ground end.

73, Ed - KL7UW
Inverted-L removed when one leg broke last fall.  Should be able to 
repair it and reinstall pretty soon as spring wx has arrived with 50F 
experienced today.

At 07:36 PM 3/31/2016, Brian Pease wrote:
>I think your reasoning is sound.  The only problem I see with open 
>turns is a possible high voltage at the open end.
>
>On 3/31/2016 10:22 PM, Frank Lotito wrote:
>>Any thoughts on what should be done with the unused turns of LF and 
>>MF loading coils?  For example, the RSGB book "LF Today, Guide to 
>>Success on 136 and 500 KHz" by G3XDV and M0BMU, 2nd edition, 
>>Figures 3-13 and 3-21.  In figure 3-13 the loading coils' unused 
>>turns are shorted. In figure 3-21 the unused turns of the 6 mH 
>>loading coil are not shorted.  We also see similar examples by the 
>>bushel full in the older literature for antenna tuners of many 
>>different configurations, PI and PI-L matching circuits, etc.
>>
>>
>>In my own station I have noticed that antenna resonant frequency 
>>changes if I remove the short at loading coil's unused turns (but 
>>feed the coil at the tap point where the short was attached.)  I 
>>can recover resonance by variometer readjustment and / or choosing 
>>another loading coil tap point.
>>
>>
>>Of course, with iron core 60 Hz AC transformers, or even a 60 Hz 
>>variac, the unused turns of a tapped winding are not shorted.  I 
>>know the reason for that.  But what about air-core coils used at LF 
>>and MF?  I would think there is some residual mutual inductance 
>>between the coil portion with the shorted turns to the active part 
>>of the loading coil.   That circulating current through the shorted 
>>turns, in my mind, acts as a loss, which means lower Q.  Obviously, 
>>we are reluctant to compromise the future utility of a higher than 
>>necessary inductance by physically removing the unused turns of an 
>>existing loading coil.
>>
>>
>>Your thoughts will be appreciated.
>>
>>
>>73 Frank Lotito  K3DZ / WH2XHA
>>
>>
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>
>
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73, Ed - KL7UW
http://www.kl7uw.com
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