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## Re: [TowerTalk] Trap Resonance

 To: towertalk@contesting.com Re: [TowerTalk] Trap Resonance K3BU@aol.com Fri, 21 Nov 2003 21:12:22 EST
 ```At 07:57 PM 11/21/2003 -0500, Joe Subich, K4IK wrote: >Get off your high horse. In a series circuit, which a loading >coil most certainly is, the current into and the current out of >a device must be the same. In the RF circuit, if the current >into and out of the coil is not the same only three things can >be happening: > >1) there is radiation > >2) there is loss > >3) the measurement is disturbing the system being measured. We are not dealing with closed circuit, but distributed and an antenna with standing waves. Here are some explanations for the phenomena: W5DXP: The key to understanding is to realize that the net current is the phasor sum of the forward current and reflected current (on a standing- wave antenna). Assume a 10 degree phase delay through the coil on the frequency of operation. Ifwd-in and Iref-out are on the same side of the coil. Ifwd-out and Iref-out are on the other side of the coil. Ifwd-in--> coil Ifwd-out--> -----------------------////////////------------------------- <--Iref-out <--Iref-in Assume that |Ifwd-in| = |Ifwd-out| which satisfies Kirchhoff Assume that |Iref-in| = |Iref-out| which satisfies Kirchhoff Ifwd-in + Iref-out = net current on left side of the coil Ifwd-out + Iref-in = net current on right side of the coil Ifwd-out lags Ifwd-in by 10 degrees Iref-out lags Iref-in by 10 degrees (Iref-in leads Iref-out) Now let's assume that Ifwd-in and Iref-out are in phase. So current on the left side of the coil equals Ifwd-in at zero degrees plus Iref-out at zero degrees which is a current maximum point. Ask yourself: Can we have a current maximum point on both sides of the coil? I trust that answer is obvious. Ifwd-out lags Ifwd-in by 10 degrees. Iref-in leads Iref-out by 10 degrees. So current on the right side of the coil equals Ifwd-out at -10 degrees plus Iref-in at +10 degrees, NOT a current maximum point. Therefore, in this example, net current on the left side of the coil cannot possibly be equal to net current on the right side of the coil. -- 73, Cecil http://www.qsl.net/w5dxp and summarized by W4JLE: If we feed an antenna at the current point, the current decreases as the voltage increases along the antenna element from feed point to end.. That being said, a coil replacing a segment of an antenna (in order to physically shorten it) will exhibit the same properties (relating to currents) as the segment it replaced. _______________________________________________ See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless Weather Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any questions and ask for Sherman, W2FLA. _______________________________________________ TowerTalk mailing list TowerTalk@contesting.com http://lists.contesting.com/mailman/listinfo/towertalk ```
 Current Thread Re: [TowerTalk] Trap Resonance, (continued) Re: [TowerTalk] Trap Resonance, K3BU Re: [TowerTalk] Trap Resonance, Red Re: [TowerTalk] Trap Resonance, Michael Tope Re: [TowerTalk] Trap Resonance, Ron & Madhavi Re: [TowerTalk] Trap Resonance, Ron Feutz Re: [TowerTalk] Trap Resonance, James McLaughlin Re: [TowerTalk] Trap Resonance, K3BU RE: [TowerTalk] Trap Resonance, Joe Subich, K4IK RE: [TowerTalk] Trap Resonance, Jim Lux Re: [TowerTalk] Trap Resonance, K3BU Re: [TowerTalk] Trap Resonance, K3BU <= Re: [TowerTalk] Trap Resonance, Michael Tope Re: [TowerTalk] Trap Resonance, K3BU