|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
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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