Grid Input Board

Remember that almost every voltage inside this linear amplifier is lethal, including the voltage levels present on this board. Turn the amplifier off, unplug it, and short out power supply rails before you touch anything. Always apply the “one hand in the pocket” principle when working on anything above 24V! Refer to the Safety chapter in the ARRL Handbook for further information on proper procedures to use when working on equipment such as this amplifier.

T1 provides impedance matching from the 50 ohm input impedance to R1, a 2.7K ohm grid swamping resistor. T1 is wound on a BN-61-202 binocular core, the 2 turn primary and 14 turn secondary providing an impedance transformation of 1:49.

Relay switched variable inductors and capacitors resonate the grid input on each band.

L1 through L6 are Coilcraft Slot Ten tunable inductors.

L7, L8, & L9 are Coilcraft Unicoil 10mm Tunable RF Inductors.

The relays are TE Connectivity IMC06CGR Low Signal Relays, PN 1462042-9.

Grid Input Board Schematic