Johnson Viking Valiant blocking capacitor change
 

Fellow boatanchor enthusiasts,

I'm going to replace the 500 pf TV style doorknob blocking capacitor
in my Johnson Viking Valiant (original not II) and will use a larger
value doorknob designed for higher RF current. I've heard 160 meter
output can be improved if a larger cap is used but have not heard what
value to strive for. Any suggestions or experience?

And don't forget the Old Gear Junk and Amplifier Builders' Net, and
the Drake and Antique Tube Gear Net.

73,

Evan,

Johnson Viking Valiant blocking capacitor change
 

Evan wrote:
Fellow boatanchor enthusiasts,

I'm going to replace the 500 pf TV style doorknob blocking capacitor
in my Johnson Viking Valiant (original not II) and will use a larger
value doorknob designed for higher RF current. I've heard 160 meter
output can be improved if a larger cap is used but have not heard what
value to strive for. Any suggestions or experience?

I'd try doubling it. There isn't really any way to have too large a value
(until you get so large that it takes some time to charge up when you put
the key down, and that's many orders of magnitude larger). However, big caps
are not cheap and I suspect you'll see diminishing returns pretty quickly.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

Johnson Viking Valiant blocking capacitor change
 

I'd try doubling it. *There isn't really any way to have too large a value
(until you get so large that it takes some time to charge up when you put
the key down, and that's many orders of magnitude larger). *However, big caps
are not cheap and I suspect you'll see diminishing returns pretty quickly..
--scott

Actually that's not true with plate modulation. The coupling cap
bypasses B+ audio through the pi network L, the safety RFC and/or a
DC path from the antenna to ground.

John, KU6X