Several amatuers are
using the 150W power amplifier and now require a suitably rated LPF, the design
shown here was developed by Ray G4TZR. We originally used "standard"
circuits given in the Radio Comunications Handbook (RSGB) but found these to
be sensitive to component tolerances and winding methods.
were made until the layout presented here produced the performance we required;
my expectation was that all harmonics should be at least 60dB below the carrier
- this design meets that criteria.
The number of turns quoted on the schematic are the actual
turns found on test with the toroids used during development; since then
they have been found to have a higher than normal AL value. Check the wound
values against the calculated values on the schematic, we believe that typically
1 turn extra on each toroid will be required.