pepewaw
Newbie level 6
Im currently designing an RF PA (in the range of 750Mhz, 10W output)
The output matching circuit to the antenna consist of segments of transmission line and variable capacitors (trimmers).
Originally, the PA oscillates, so I try adjusting the trimmers. The thing is, I don't have a plastic screwdriver for adjusting them, so whenever I touch the trimmers with a metallic one, I modify the output matching circuit.
There's a trimmer configuration, where If I touch one of the trimmers with the metallic screwdriver the PA works great, but as soon as I let go it oscillates or gain drops (And I can't seem to get that state besides touching the trimmer).
My question is, whats the effect of a metallic screwdriver and a person holding it on a trimmer, so that I can simulate such 'circuit' with discrete components? (for instance, if touching it makes the capacitance higher, i may add a parallel capacitor so that I dont have to touch it to make it work; or maybe the effect is that of an open transmission linem, you get the idea)
Thanks for any feedback.
The output matching circuit to the antenna consist of segments of transmission line and variable capacitors (trimmers).
Originally, the PA oscillates, so I try adjusting the trimmers. The thing is, I don't have a plastic screwdriver for adjusting them, so whenever I touch the trimmers with a metallic one, I modify the output matching circuit.
There's a trimmer configuration, where If I touch one of the trimmers with the metallic screwdriver the PA works great, but as soon as I let go it oscillates or gain drops (And I can't seem to get that state besides touching the trimmer).
My question is, whats the effect of a metallic screwdriver and a person holding it on a trimmer, so that I can simulate such 'circuit' with discrete components? (for instance, if touching it makes the capacitance higher, i may add a parallel capacitor so that I dont have to touch it to make it work; or maybe the effect is that of an open transmission linem, you get the idea)
Thanks for any feedback.