An operator cannot live by QRP alone! Sometimes fire bottles are needed.

Here's a peek at the "business end" of a pair of 813 beam-power tetrodes, operating as grounded-grid triodes in a Class AB2 linear amplifier at AI2Q.

Here's the front panel of the bandswitched 813 rig, built in 2000.

The solid-state power supply is fully metered, with B+ adjustable by means of a Variac.

This rig is usually operated on either 40-M or 20-M.

This bandswitching amplifier covers 80-M through 15-M. It was built in 1976 at AI2Q, and has seen continuous service ever since.

It runs a neutralized pair of 572-B Svetlana triodes in grounded-grid Class AB2 service. A solid-state power supply is built-in.

It's typically driven either by a Ten-Tec Omni-V transceiver, a Heathkit SB-401 (with SB-303 as a receiver), or a Drake TR7A transceiver.

This rig is usually operated on 80-M CW. It uses a Jennings DPDT vacuum changeover relay for QSK. Output power is 700-W.

This PA is dedicated to 160-M CW and SSB operation.

It uses a pair of 8188 tetrodes operated in grounded-grid Class AB2 service.

The 8188 (also known as 4-PR400As) tubes are the pulse-rated equivalents of 4-400A tetrodes. They carry a 25 kV plate voltage spec! This PA is also equipped with a Jennings vacuum changeover relay for QSK operation on CW.

In this view you can see the parallel 8188 tubes warming the shack.

The PA's power supply includes a Variac to permit adjustment of the B+. The power supply in this PA was initially based on a pair of microwave oven transformers.

Subsequently, W1YBR furnished a FB commercial supply. I added a time-delay inrush circuit and some metering to it, and pressed it into service. The new supply easily permits the PA's output to be 900-W continuous into a 50-ohm load.

The main operating position at AI2Q also includes a 2-kW Heathkit SB-220 linear amplifier.

It uses a pair of 3-500Z triodes, and is operated on CW and SSB modes on 80/75-M, 40-M, 20-M, 17-M, 15-M, 12-M, and 10 meters.

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