[ARC5] Smart People: Antenna Matching Mystery

[arc5@ix.netcom.com]

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------ Original message------From: J McveyAntenna Matching Mystery
...The 50 ohm coax at the terminal causes a host of reactance and reflection issues by itself.Bet if you added coax length, the situation would change to something else, maybe better, maybe worse!
RF is spooky stuff!!
 ----You are so right.  I switched the coax jumper to a long one, coiled into a big spool "shield RF choke."  It completely changed the tuning.  RF is Electronic VooDoo.73 Dave S.
    On Monday, August 7, 2017 10:13 AM, Ian Wilson > wrote:
  

 I have noticed that the roller coil has distributed capacitance, so itdoes not always behave as a simple inductance even at lowly RF.
To a reasonable approximation, it could probably be modelled as"a few" L-C sections. 4 would be a good starting point.
73, ian K3IMW
On Mon, Aug 7, 2017 at 6:57 AM, David Stinson <arc5 at ix.netcom.com> wrote:
OK y’all- here’s a mystery (at least to me),Series circuit, designed to match a normally 5-12 OhmAircraft radio output to resistive 50 Ohms. Follow me here: Series circuit:PA Tank coupling link – Roller coil – 120pFd ceramic cap mounted at antenna post – 50 Ohm Load = 25 W out. PA Tank coupling coil –  120pFd ceramic cap mounted at the input of the Roller Coil – Roller Coil –50 Ohm Load = 15W out. The ceramic cap is near chassis ground both ways,so it’s not circulation currents.The PA tuning cap setting does not change,so it’s not de-tuning the PA tank.  Why the difference between these two series circuits? 73 Dave AB5S  
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