[HomeBrew] Plate Choke

[N2EY at aol.com]

In a message dated 5/13/07 8:38:42 PM Eastern Daylight Time, 
rickbras at airmail.net writes:


> Generally speaking, am I correct in calculating a plate choke for a 160
> meter transmitter should be somewhere in the 5 - 6 mh range and about 10Ù in
> resistance? 

No. There are lots of factors to consider.

The first one is the output impedance of the tube (you did write "plate 
choke").
The usual rule of thumb is that the choke reactance should be ten times the 
output Z of the tube. A 5.0 millihenry choke, on 2.0 MHz, has a theoretical 
impedance of 62,800 ohms, so it should be good up to an output Z of 6280 ohms. 
Say 6000 ohms in round numbers. 

Depending on the tube(s) you are planning to use, and the mode of operation, 
the output Z of a tube amp may be much lower than 6000 ohms, or much higher. 

If it's much higher, 5 mH isn;t enough. If it's much lower, you could use a 
lot smaller choke.

You have to know the output Z first. 

As for the 10 ohms DC resistance, it depends on the plate current. More 
important is the current rating of the choke.

What operating conditions are you planning on?

73 de Jim, N2EY


**************************************
 See what's free at 
http://www.aol.com.