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More Original RCA Data

The RCA Pitch Resonant Coil

Consists of more than a thousand turns of approximately 38 ga. ( B&S gauge) SSC enameled wire wound on a 12" tall by a 2 15/16" diameter, 1/16"-wall phenolic impregnated fiber tube.

Winding length- 10 3/4"
DCR 445 ohms
Z at 1kHz 531 ohms
Inductance 31 mH

In series with the big coil is the so-called "concentrated coil". It is fitted planar fashion inside the bottom of the large coil. An air-core, low self-capacity, RF choke. 1" diameter lattice wound, 7/16" thick, wound in fine, enameled wire on a 1/2" diameter wooden spool. The concentrated coil contributes the remaining inductance needed for a 175kHz-resonant system. There wasn't enough room on the big coil form for all that wire.

DCR 100 ohms
Inductance 18.6 mH

Between the two coils there is a small blocking cap (.0022??) presumably to prevent DC voltage ever getting to the antenna and posing a shock hazard. At any rate the cap doesn't appear sized for tuning/peaking purposes.

The RCA Volume Resonant Coil

employs the same 38 ga. SSC wire and the same size tubular form as the big pitch coil. The winding length is only 4 1/4". Inductance measures 11.9mH.

The volume pick-up coil consists of eight turns of ~ 20 ga. wire placed over the volume resonant coil, right at the lower (hot) end of the big coil's winding length.

[Copyright 1997 by Reid Welch]


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