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

[Edward R Cole]

OK  Q = X/R, so if R decreases Q increases. But a coil with less 
turns has less inductance so X also drops.

My point is who cares if Q decreases, since our base-loaded very 
short verticals have way too much Q.

BTW I tuned a filter for better impedance match by shorting a turn in 
a coil.  No change in insertion loss. Runs at 1000w!  It did affect 
the rejection loss of the filter somewhat.  So called coil formula 
did not work in real-world ckt.  So in true ham spirit I tweaked 
it!  BTW the coil is in use at VHF.
http://www.kl7uw.com/6m_LP_filter1.jpg

Good 2nd harm rejection > 50 dB and amplifier runs very happy into 
matched impedance.

73, Ed

At 01:28 PM 5/7/2018, J Mcvey wrote:
>"Hmm.  If you short a turn the coil is shorter and has less 
>resistance.  If you lower-Q that is good."
>
>
>
>
>You are confusing series wire resistance with induced effective 
>resistance. ( this is how transformers work)
>
>One of the possible tests for Q is called a 'ring test" where the 
>longer the ring time, the greater the Q.
>
>If you are losing energy into a shorted turn , there will be fewer 
>rings and lower Q.
>Even if you short a turn in the active area of a coil you will kill 
>the Q. , unused portions of coils are often shorted to avoid HV 
>buildup on the unloaded  part.,  but never to modify the active part.
>
>On Monday, May 7, 2018, 4:08:12 PM EDT, Edward R Cole 
><kl7uw at acsalaska.net> wrote:
>
>
>Hmm.  If you short a turn the coil is shorter and has less 
>resistance.  If you lower-Q that is good.  My antenna Q is so high, 
>bandwidth is only 5-6 kHz.  I fattened my antenna to lower Q.
>
>Can any ham actually measure the effect of a tuning loop inside a 
>coil?  I mean efficiency.  How is a variometer any different in effects?
>
>73, Ed - KL7UW
>
>At 08:47 AM 5/7/2018, J Mcvey via 600MRG wrote:
>>OK, but a shorted turn will also reduce the overall Q as well.
>>It will also sap energy.
>>I think we don't see this method in newer stuff for good reason...
>>
>>
>>On Monday, May 7, 2018, 12:00:25 PM EDT, Kenneth G. Gordon 
>><kgordon2006 at frontier.com> wrote:
>>
>>
>>On 7 May 2018 at 14:11, J Mcvey via 600MRG wrote:
>>
>> > 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?
>>
>>That, in fact, is the whole point. National used a similar device, 
>>a shorted turn, in the coils
>>for the HRO to enable adjustment of the inductance to aid in tracking.
>>
>>Ken W7EKB
>>
>>---
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>73, Ed - KL7UW
>   <http://www.kl7uw.com/>http://www.kl7uw.com
>Dubus-NA Business mail:
>   dubususa at gmail.com

73, Ed - KL7UW
   http://www.kl7uw.com
Dubus-NA Business mail:
   dubususa at gmail.com 
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