[Boatanchors] Tuning Capacitor Air Gap Information

[Greg]

Hi:
I was leafing thru the 1942 edition of the Radio Handbook pg 177 and came across some useful information for the voltage ratings of transmitting variable capacitors.  This subject comes up from time to time on the reflectors.

The data table is prefaced with this:
" The rf voltage in the plate circuit of a class C amplifier tube varies from nearly zero to twice the DC plate voltage.  If the dc voltage is being 100 % modulated by an audio voltage, the rf peaks will reach four times the DC voltage. These are the highest values reached in any type of loaded amplifier: a class B linear, class C grid or plate modulated, or class C cw amplifier."
Data table:
Air gap in inches            Peak Voltage breakdown
.03                                 1000
.05                                 1500
.07                                 3000
.078                               3500
.084                               3800
.1                                   4150
.144                                5000
.175                                5700
.2                                    6200
.25                                  7200
.3                                    8200
.35                                  9250
.375                               10000
.5                                   12000

73's
Greg
WA7LYO
Kinston NC