. QST . e of two popular impedance lev-els. On the lower-frequency bands the antennacouples to Li through a primary winding, andunder these conditions the ANT TRIM panelcontrol (a small variable across C2) is trulyan antenna trimmer. When the 6AB4 is inthe circuit, the ANT TRIM becomes a trim-mer control to bring the stages into align-ment. Since the value of i?i is increased on Fig. 2 — Simplified schematicdiagram of the grounded-grid used above Mc. Ri, Ciand Li are switched for the variousranges and have different valueson the various bands. Ti is thesame on all bands. the
. QST . e of two popular impedance lev-els. On the lower-frequency bands the antennacouples to Li through a primary winding, andunder these conditions the ANT TRIM panelcontrol (a small variable across C2) is trulyan antenna trimmer. When the 6AB4 is inthe circuit, the ANT TRIM becomes a trim-mer control to bring the stages into align-ment. Since the value of i?i is increased on Fig. 2 — Simplified schematicdiagram of the grounded-grid used above Mc. Ri, Ciand Li are switched for the variousranges and have different valueson the various bands. Ti is thesame on all bands. the higher-frequency ranges, the gain of thegrounded-grid stage increases in these ranges. Getting back to the over-all picture, thegrounded-grid stage is followed by a more stage. The 6AG5 oscillator is coupled intothe cathode circuit of the 6AU6 mixer. In thetwo lowest-frequency ranges the output of the6AU6 mixer is switched into the 6BA6 stage at 455 kc, but on the higher-frequency. ranges it is switched into the 6BE6 converterstage. The grid circuit of the 6BE6 has threecircuits tuned to Mc, and its oscillatorcircuit is self-controlled. The manufacturer statesthat no appreciable improvement in stabilitycould be gained by using crystal control at thispoint. With the 6BE6 converter active, the6BA6 buffer is not used. The crystal filter circuit is similar to that usedin most receivers today, and has provision forfive degrees of selectivity. The SELECTIVITYswitch on the panel is marked in bandwidths atthe — 3 db. points, and these range from 200 to feAB4 6CB6
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectradio, bookyear1915
