Updated 9-17-2002

Round the World Four

   In 1927-28 there were available on the market several short wave receiver kits which are easily assembled by the amateur set builder. One such kit of particular merit, designed and sold by Silver-Marshall, Inc., of Chicago, is known as "Round the World Four." This kit employs one stage of untuned radio frequency amplification preceding the detector tube. A description of the kit follows.

   Description-- Silver-Marshall "730 Series" screen grid short wave kits were available in two models, both of which were designed around a type 732 Essential Kit. Both are identical in external appearance, being housed in the same type of aluminum shielding cabinet, 14 inches long, 6 inches wide and 6 inches high, and weighing 14 pounds. The 730 "Round the World Four" is a four-tube non-radiating short wave receiver consisting of one stage of screen grid r.f. amplification, a regenerative detector and two stages of extremely high-gain audio amplification.

   Four inductance coils, which may be successively plugged into a 5-prong tube socket on top of the cabinet, provide four tuning ranges on the left-hand (tuning) dial (131-T: 17.4 to 32 meters. 131-U: 31 to 58 meters. 131-V: 56 to 110 meters. 131-W: 105 to 204 meters).
The right-hand vernier dial controls regeneration. The small lower knob regulates the detector filament voltage, and at the extreme anti-clockwise position turns the entire set off.

   The loud speaker range is practically unlimited, being restricted only by atmospheric conditions, operating location, and transmitter power. Ordinarily, under favorable conditions, European short wave broadcast stations may be received, and amateur code stations on every continent may usually be tuned in all in a single evening. In Chicago, low power amateur telephone stations from Maine to California were received loudly and clearly.        [ Click on the photo to enlarge it. ]

Click on image below for actual photo of the radio.

Assembly of Silver-Marshall "Round the World Four" Receiver.
(When installed in the cabinet, the receiver is actually upside-down.)

   The 731 "Round the World Adapter" is essentially a two-tube device used for short wave reception, when connected by an adapter to any broadcast receiver. Or it may be connected to a standard power audio amplifier, or used directly with headphones. The 731 adapter is exactly the same in appearance as the 730 four-tube set, and is substantially the 730 set except that the two-stage audio amplifier is omitted (but may be added at any time if desired). The wavelength range, tuning characteristics, distance range, etc., are the same for Model 731 as for Model 730.

   Type 732 Essential Kit contains the essential parts for the r.f. portion of the S-M "Round the World" circuit. It may be assesmbled into a two-, three-, or four-tube receiver, as desired, either in the S-M type 734 aluminum shielding cabinet, or upon a wood baseboard, or in any other fashion.

Circuit Diagram of Silver Marshall "Round the World Four,"
a 4-Tube Screen-Grid Short Wave Receiver.
A larger version of this schematic is in the Adobe "pdf" file below.

Information is from "Radio Manual" by George E. Sterling, 1928. Edited for the Web by John Dilks, K2TQN.© 1999.