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Re: [TowerTalk] antenna choices for K4XS

To: Doug Smith <doug@w7kf.com>
Subject: Re: [TowerTalk] antenna choices for K4XS
From: Bry Carling <bcarling@cfl.rr.com>
Date: Tue, 14 Apr 2015 15:29:41 -0400
List-post: <towertalk@contesting.com">mailto:towertalk@contesting.com>
How many watts do you then suppose is being dissipated in a trap on your 
average tribander running at 1500watts out?

Just a typical number. Take the worst case scenario. Empiricist that I am, I 
would bet it's less than 10 watts per trap, and hardly significant. You would 
need to be losing at least 50-100 W per trap to even be able to notice any 
difference on the receiving end using instruments, let alone with the human ear.

Don't burn your fingers on those traps :)

Best regards - Brian Carling
AF4K Crystals Co.
117 Sterling Pine St.
Sanford, FL 32773

Tel: +USA 321-262-5471




> On Apr 14, 2015, at 1:16 PM, Doug Smith <doug@w7kf.com> wrote:
> 
> 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).
> 
> 73,
> Doug, W7KF
>  http://www.w7kf.com
> 
> 
>> On Apr 14, 2015, at 10:32 AM, Bry Carling AF4K <bcarling@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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