[TowerTalk] Antenna Coupler Capacitor Settings

[on4kj]

Just that simple .........for a radio amateur....... sorry guy's

73's Jos


----- Original Message ----- 
From: "Chuck Counselman" <ccc at space.mit.edu>
To: <TOWERTALK at contesting.com>
Sent: Friday, January 31, 2003 11:40 PM
Subject: Re: [TowerTalk] Antenna Coupler Capacitor Settings


> Here's how to determine when your C-L-C T-network antenna tuner's 
> output capacitor (or if you choose, its input capacitor), is fully 
> meshed -- without opening the box.
> 
> You need a multimeter (like my Radio Shack DMM) or an impedance 
> bridge that can measure capacitance at a low frequency, preferably 
> below 1 MHz.
> 
> Measure between the "hot" and "ground" terminals of the output 
> (antenna) end of the tuner.  Crank or switch the tuner's inductor all 
> the way down to its smallest possible inductance, which would be at 
> the end or the extreme setting that you use for the highest 
> frequency.  The minimum inductance of the coil is probably around one 
> microhenry.  At 1 MHz or below, this inductance has a reactance of 
> about 6 ohms or less.  This reactance is negligible in comparison 
> with even the smallest possible reactance of the output capacitor of 
> a typical antenna tuner.  The maximum capacitance of one of these 
> cap's is typically 240 pf; the reactance of 240 pf at 1 MHz is -663 
> ohms.  Therefore, with your meter, you are effectively looking 
> directly at the capacitor.
> 
> Now turn the knob on the output (antenna) capacitor and watch the 
> meter or bridge to find the maximum C.
> 
> -Chuck, W1HIS
> 
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