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

[J Mcvey]

 "Hmm.  If you short a turn the coil is shorter and has lessresistance.  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 lessresistance.  If you lower-Q that is good.  My antenna Q is sohigh, bandwidth is only 5-6 kHz.  I fattened my antenna to lowerQ.

Can any ham actually measure the effect of a tuning loop inside acoil?  I mean efficiency.  How is a variometer any different ineffects?

73, Ed - KL7UW

At 08:47 AM 5/7/2018, J Mcvey via 600MRG wrote:

OK, but a shorted turn will alsoreduce the overall Q as well.
It will also sap energy.
I think we don't see this method in newer stuff for goodreason...


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 tuningunits.
> 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, ashorted turn, in the coils 
for the HRO to enable adjustment of the inductance to aid intracking.

Ken W7EKB

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 73, Ed - KL7UW
 http://www.kl7uw.com
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