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A high-powered grounded-grid linear amplifier

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Ed Brown, W9ROQ, has a pair of 304TLs in his 14 Mc output amplifier driven by the p.p. 811A rig in the Handbook. The 304s are in the grounded-grid circuit shown in Fig. 1, and Brownie says it is about the most foolproof amplifier he ever tried. The 240 volt bias is obtained from a VR-150 and a VR-90 in series, and this holds the idling current to around 100 mA. On peaks, the indicated plate current is around 300 mA. Parasitic suppressors were originally included in the plate leads but they were found to be unnecessary.

Fig 1
Fig. 1. The 14 Mc grounded-grid linear at W9ROQ uses a pair of 304TLs.

C1100 pF-per-section variable.
C250 pF-per-section variable.
All other condensers are 4 nF 600 volt mica.
L120 double turns No. 12 enam., wound on 1 inch diam. form.
L2B & W HDVL-20.
RFC1R.f. choke (National R-175).