September 1935 QST
Table of Contents
Wax nostalgic about and learn from the history of early electronics. See articles
QST, published December 1915 - present (visit ARRL
for info). All copyrights hereby acknowledged.
metal-encased vacuum tubes came on the electronics
scene in the 1930s, they were billed as the innovation that was going to radically change the radio world. The built-in
Faraday shield properties of the tubes did in fact stop the effects of cross-coupling between adjacent tubes and permit
more densely packed circuits, but they also caused some other problems as well. Capacitance between tube elements and the
shield caused electron flow control issues and affected operational frequency. Packing tubes closer together also meant
the rat's nest of resistors, capacitors, inductors, and wires on the underside of the chassis that were installed in a point-to-point
manner rather than neatly on printed circuit boards (which largely did not exist at the time) were closer together and therefore
created new problems due to proximity. Still, metal tubes served a very useful purpose when employed wisely and continued
in use along with unshielded tubes right up until transistors and PCBs dominated the electronics market.
General Electric Radio Advertisement
Hark Ye, 'Phone Men!
The New All-Metal Tube
The new tubes - "sealed in steel" - invented and perfected by General Electric engineers - have many improved electrical
characteristics. Here are a few of the highlights.
1. More effective shielding allows higher I.F. gain with stability.
2. Higher I.F. gain means - greater signal on diode, less harmonic distortion on high modulation -
less audio gain required, quieter operation.
The New General Electric Radio with All Metal Tubes
Mail Coupon for Details
General Electric Company,
1 Bridgeport, Conn.
Attention: Sales Promotion Section R-159:
Please send me complete details regarding General Electric Radios with the All-metal Tubes.
The 1936 General Electric Radio with new all-metal tubes brings to amateur operators the latest advancement in radio
science and engineering. Its fidelity and crisp clear-cut reproduction is far in advance of the field.
Model A-82 ... An all-purpose receiver, scientifically designed for the many exacting demands of modern amateur stations.
The following outstanding features will appeal to all hams.
• Air Trimmers - provide better calibration stability • Sliding-rule Tuning Scale - easy to read as a ruler • Improved
A.V.C. due to higher I.F. gain .• 5 Watts undistorted output delivered to 10 in. high-quality dynamic speaker. • Frequency
coverage 140-410 and 540-19,500 KC in 4 bands .• CW oscillator may be added.
Merchandise Department, General Electric Company, Bridgeport, Connecticut
Posted May 18, 2016