Click above for
Table of Contents
by Don Adamson
If you appreciate ingenuity, simplicity, and like instant gratification from your radio projects, then you ought to spend a few minutes building your own foxhole radio.
Here is some more information on the foxhole radio sets used by the boys on the Anzio beachhead. In the daytime they could receive stations from Rome and at night Nazi propaganda "jive" programs from Berlin. Here is the diagram:
In the "Strays" section of QST for July, 1944, another mention is made of the razor blade foxhole radio:
According to Toivo Kujanpaa, a licensed ham op stationed on the Anzio Beachhead, several of the radio men there rigged up a field version of a "crystal" set using a razor blade for a detector. Their efforts were rewarded by the reception of a "jive" program (along with some German propaganda) aimed at the American forces from an Axis station in Rome.
Note the simplicity of the design. Parts were assembled on a piece of wood, usually held in place with thumbtacks. The safety pin is anchored at one end and placed so the point may be moved around on the surface of the razor blade. According to an article in Popular Mechanics of October, 1944, the blued steel surface of the blade gives the rectifying action needed for detection without crystals.
The design below came from a submission by Lt. Paul M. Cornell in the September, 1945 issue of QST; he used it in the South Pacific. The photograph shows a similar radio built by Don Menning; he simply stuck the whole tip of a pencil on the end of the safety pin.
Here is the parts list for the schematic based on Lt. Cornell's submission:
(A) Antenna connection. This nail also fastens the coil form to the baseboard.
(B) Baseboard. 4 inches square, ¼ inch thick.
(C) Coil form. Wood block, 3¾ inches long, 2 inches wide and ¼ inch thick.
(D) Area of coil scraped clean along arc of switch arm.
(G) Ground connection. This nail also fastens coil form to baseboard.
(J) Jacks for 'phones. Paper clips held down by tacks.
(P) Detector. Pencil lead wrapped with copper wire and resting lightly on razor blade. Some adjustment of the location and pressure of the lead on the blade may be required.
(R) Razor blade held down and connected to wire by tack.
(S) Screw or nail for pivot of switch arm.
(SA) Switch arm made from paper clip.
(T) Thumbtack, or any kind of tack.
(W) Coil winding, approximately 175 turns No. 26 insulated wire.
In October of 1962, Popular Mechanics ran a construction article by Joe Tartas which was almost identical to the above design. Mr. Tartas noted that GIs used their bayonets buried to the hilt in moist earth for a ground connection. You probably do not want to use your vintage WWII bayonet in this manner unless you're a stickler for authenticity!
Disclaimer: Working with antennas and electrical devices (especially old ones) can be dangerous, and mistakes can be fatal. If you decide to work with such things, it is solely your responsibility to work safely and to know what you're doing. -DJA
Copyright © by Don Adamson. All Rights Reserved.