I am using a 25 ohm 50w wirewound glitch resistor immediately after the
plate choke. I have 0.01 uf 6 kV discs in parallel with 0.001's on both
sides of the resistor and at the HV connector. I presume that the resistor
functions as a choke.
On 10/9/2013 4:37 AM, Jim Thomson wrote:
### points well taken. The typ 50 uh choke will resonate at aprx 35
mhz...so no worry about series resonances in ham bands.
That’s actually a good design. I have no clue how much rf Voltage..is
too much ? But with tubes with handles etc, we are dealing with way
more than 2000 V...so the simple extra LC would be of a great
benefit...and easy to implement.
Jim VE7RF
-----Original Message----- From: peter chadwick
Sent: Wednesday, October 09, 2013 4:03 AM
To: Jim Thomson ; [1]amps@contesting.com
Subject: RE: [Amps] LF oscillation caused by defective plate choke?
### 250 uh is fine for the plate choke. Instead of the 1000 pf
bypass cap, use 2-3 x 4700 pf disc ceramics. That combo makes for an
excellent lower freq bypass cap.
Then wire 1-3 x 500pf ceramic doorknob caps in parallel with the 4700 pf
caps. The 500 pf caps make for an excellent higher freq bypass cap.<
You will have about 1 volt across that combination on 80m. Using 1 4700 pF
cap and 1 500 pF cap in parallel will give 3 volts: then a 50 microhenry
choke and another 4700 pf will drop this to 27mV and you have saved 1 or 2
500 pF caps and 1 4700 pF cap and got a better result. Just adding
capacitors gets to a state of diminishing returns.
73
Peter G3RZP
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