[Fox_Tango] FT-101-E neutralizing circuit

[Kevin J Ward]

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

________________________________________________________________
GET INTERNET ACCESS FROM JUNO!
Juno offers FREE or PREMIUM Internet access for less!
Join Juno today!  For your FREE software, visit:
http://dl.www.juno.com/get/web/.