[TowerTalk] antenna choices for K4XS

Doug Smith doug at w7kf.com
Tue Apr 14 13:16:52 EDT 2015

Losses in an inductor are related to both the Q of the inductor and the current flowing through it.  

Simplistically, one could think of it as:  P(loss)  =  I^2 * R.

So, given the same Q, in a high voltage, low current scenario (like the RF tank coil in your amp) the losses will be less than in a higher current, lower voltage scenario (antenna trap).

Inductors in antenna traps are usually low Q affairs due to the physical constraints imposed upon them.  Thus, higher losses even without any operational faults such as you describe.  And, they’re usually in a fairly high current area of the antenna.  Again, resulting in higher losses..

I have an inductor in an L-network that, on 80 meters, has 17 amps flowing through it.  You can bet your last dollar I have taken every step possible to make sure the Q of that inductor is as high as I can make it.  (Huge, silver plated, enclosure is non-conductive, etc.)  That inductor is MUCH larger than the tank coil in the amp driving it.  But it has much more ability to make heat than the inductor in the tank circuit, due to the nature of the circuit it is in.  It has many more amps flowing through it even though the amount of power is the same (1.5 KW).

Doug, W7KF
 http://www.w7kf.com <http://www.w7kf.com/>

> On Apr 14, 2015, at 10:32 AM, Bry Carling AF4K <bcarling at cfl.rr.com> wrote:
> Then there would also be the issue of your RF tank coil in a linear amplifier being similarly 
> "metal enclosed."  Somehow I am not seeing your point.

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