[Milsurplus] [ARC5] Smart People: Antenna Matching Mystery

[Dave Jackson]

Just a thought:

 

At the antenna side of the coil, the impedance is 50 ohms resistive- a
simple I^2 R problem.  At the transformer end it the impedance is probably
much lower resulting in a greater current in the cap with attendant
increasing loss.  This is probably a complex impedance at the transformer
end and power is not a simple I^2*R calculation.

 

Additional stray capacitances would add to the problem.

 

Sincerely,

 

Dave WA4OBJ

 

From: arc5-bounces at mailman.qth.net [mailto:arc5-bounces at mailman.qth.net] On
Behalf Of David Stinson
Sent: Monday, August 07, 2017 6:58 AM
To: ARC-5; milsurplus at mailman.qth.net
Subject: [ARC5] Smart People: Antenna Matching Mystery

 

OK y'all- here's a mystery (at least to me),

Series circuit, designed to match a normally 5-12 Ohm

Aircraft 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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