Concerning,
"...At 80 meters, 100uH has a
reactance of 2.2 kiloohms. At 1000V RF, that would make 0.45A of RF
current going through the choke, and this is the current that the bypass
cap has to conduct to ground, unless there is something else
helping...(etc.)"
Plate solenoid choke rated values of inductances are measured at a low audio
frequency. At RF frequencies they exhibit much, much higher effective
impedances of up to over a megohm at their first fundamental parallel self
resonance, which is ideally put into use for highest efficiency. At
frequencies lower than the first parallel self resonance, they still reflect
typically ballpark Zs of about 30,000 ohms or much more to the plate tank
circuit. This is due to the principle of many self-parallel resonances
within the windings. So on 80 meters at 1000 volts RF, current through the
bypass cap would be on the order of only 30 mA or 0.03 A for a 100 uH choke,
maximum...even smaller currents are likely in practice due to surrounding
grounded surfaces lowering the primary resonant point. Stay away from
fundamental series resonances. References are from Ohmite plate RF choke
engineering papers.
73, Roy K6XK
_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps
|