[Amps] Pi-L network

[Peter Voelpel]

I also found out that decoupling of the coils does the trick.
With a single coil layer and the loading cap simply tapped to it, it was
much worse.

The Racal TA1800 with a 4CX10000D in AB1 is 2-30 autotune, specified at 10KW
out and harmonics -53db down.
It is also using Pi-L with two vacuum variables and two roller inductors,
the Pi section is ganged.
Coils are 90° to each other, capacitors close together and to the tube.


73
Peter

-----Original Message-----
From: amps-bounces at contesting.com [mailto:amps-bounces at contesting.com] On
Behalf Of zl1aih at ihug.co.nz

I'm working on a JRC-510 transmitter - 1.6 to 30mHz continuous, 5kW out,
passive grid-driven AB1 tetrode.
It uses a Pi-L network (switched fixed capacitors, roller inductors,
auto-tune) - the manual states >50dB harmonic/spurious suppression.

>Tom said:    Do you partition or shield the L coil from the main tank 
coil and tube leads??>

The JRC-510 has a vertical partition between the tube and Pi section, and
the L section - very serious shielding.

Another amplifier here, Sunair GL-1900 -1.6 to 30mHz continuous, 1 kW out
passive grid-driven AB1 tetrode - Pi-L network (vacuum C, switched L, vacuum
C, roller L, auto-tune) also has a shield between the tube/Pi
inductor/capacitor section and L2 and C2.

I assume that the shielding was to eliminate any unwanted coupling between
the two L networks.