[Amps] Relationship between Q and SWR in PI network.

[Paul Baldock]

Does anybody know the relationship between Q and SWR for a PI network?

For example let's say I design my amp PI output network for 7.0MHz. I 
simulate the Tube Impedance with a 1K resistor. I put my MFJ259 on 
the output of the PI and tweak the load and tune caps for a perfect 
1:1 (50 Ohm) SWR. I now leave the caps where they were and adjust the 
frequency to show the upper and low 2:1 SWR points and they are 
7.2MHz and 6.8MHz. (2:1)=Fo/(Fu-Fl)=7.0/(7.2-6.8)=17.5. In practice 
this is in fact about 1.5 times my design Q, but I would like to know 
what theory says.

- Paul  KW7Y