[Fox_Tango] FT-101-E neutralizing circuit

[Arthur Nelson]

--- Kevin J Ward <kevin_ward@juno.com> wrote:
> Concerning the FT-101-E:
> 
> I have been following the thread about changing the
> value of the fixed
> 100pf series capacitor in the neutralizing circuit. 
> We are all trying to
> read the mind of the designer after the fact, and
> wondering if the
> arrangement is unnecessary.
> 
> The 10pf variable capacitor has a nominal voltage
> rating of 1500 volts. 
> That figure could vary somewhat as the capacitor is
> adjusted.  Dust or
> other particles between the "plates" of the
> capacitor could further lower
> the breakdown voltage, as pointed out by N5PGH.  Now
> consider the RF
> voltage distribution between those two capacitors;
> the 100pf fixed and
> 10pf variable.  The voltage across the variable will
> be 91% of the total.
> 
> Without the fixed series capacitor, any arcing
> across the neutralizing
> capacitor COULD destroy the driver tube, and
> possibly other components as
> well.  Reducing the capacitance of the fixed
> capacitor equalizes the
> voltage drops and reduces the likelihood of
> flashover at the variable. 
> As KF6IIU pointed out, this hardly affects the
> neutralizing  process at
> all.  In fact, it may make adjustment less critical.
> 
> Kevin
> N2IE

I replaced the 100pf fixed cap in mine with a 10pf
unit and opened the variable to full open and from
there it came into neutralization very easily so it
does indeed make the adjustment less critical.

Art WB9HNJ

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