The Ambient Power Module (APM) is a simple electronic circuit
which,when connected to antenna and earth ground, will deliver low voltage up
to several milliwatts.
The amount of voltage and power will bedetermined by local radio noise levels
and antenna dimensions.
Jes Ascanius Version of Nikola Tesla's Aerial System
Generally a long wire antenna about 100' long and elevated in a
horizontalposition about 30' above ground works best. A longer antenna may be
requiredin some locations. Any type copper wire, insulated or not, may be used
for the antenna. More details about the antenna and ground will be
The actual circuit consists of two oppositely polarized voltage doublers (Figure 1). The DC output of each doubler is connected in series with the other to maximize voltage without using transformers. Single voltage doublers were often found in older TV sets for converting 120 VAC to 240 VDC. In the TV circuit the operating frequency is 60 Hz.
The APM operates at radio frequencies, receiving most of its power from below 1 MHz. The basic circuit may be combined with a variety of voltage regulation schemes, some of which are shown in Figure 2. Using the APM-2 to charge small NiCad batteries provides effective voltage regulation as well as convenient electrical storage. This is accomplished by connecting the APM-2 as shown in Figure 2B.
Charging lead acid batteries is not practical because their internal leakage is too high for the APM to keep up with. Similarly, this system will not provide enough power for incandescent lights except in areas of very high radio noise.
It can be used to power small electronic devices with CMOS circuitry, like clocks and calculators. Smoke alarms and low voltage LEDs also can be powered by the APM.
Figure 3 is a characteristic APM power curve measured using
loads from 0-19 kOhm. This unit was operating from a 100' horizontal
about 25' high in Sausalito CA. As can be seen from the plot, power
rapidly as the load resistance decrease from 2 kOhm. This means that
voltage, high impedance devices, like digital clocks, calculators and
alarms are the most likely applications for this power source.
Some applications are shown in Figures 4 through 7.
Figure 4. A digital clock is shown powered by the APM-2. The 1.5
clock draws 28 microamps. Its position on the power envelope curve
be off the scale to the right
and almost on the bottom line, dissipating only 42 microwatts.
Figure 6 shows a clock which has the APM-2 built into it so it is
necessary to connect the antenna and ground wires directly to the
The antenna for this clock, which is a low frequency marine type, is
in Figure 7.
These antenna are expensive, not generally available, and usually don't work any better than the long wire mentioned above. But it may be necessary to use them in urban areas where space is limited and radio noise is high.
Building the Module
The builder has a choice of wiring techniques which may be used to construct the module. It may be hand wired onto a terminal strip, laid out on a bread board, experiment board, or printed circuit. Figure 8 shows some of the different ways of constructing the APM-2.
Figure 8A is constructed on a screw strip terminal; Figure 8B is constructed on a perforated breadboard; Figure 8C is built on a standard experiment board; Figures 8D, 8E, and 8F are all printed circuits; Figure 8F is made up on a solder strip terminal.
If you wish to make only one or two units, hand wiring will be most practical, either on a terminal strip or breadboard. Assembly on the terminal strip (Figure 8A) can be done easily and without soldering. It is important to get the polarity correct on the electrolytic capacitor. The arrow printed on the side of the capacitor points to negative.
Figure 9 is a closer view of the terminal strip with an illustration of the components and how they are connected.
The breadboard unit is shown in Figure 10 with all components on one side and all connections on the other. All you need is a 2" x 2" piece of perforated breadboard (Radio Shack #276-1395) and the components on the parts list. Push component wires through the holes and twist them together on the other side. Just follow the pattern in the photo, making sure to observe the correct polarity on the electrolytic capacitors and the diodes. The ceramic capacitors may be inserted in either direction.
The experiment board unit is assembled by simply pushing the component leads into the board as shown in Figure 11. This unit is powering a small red LED indicated by the arrow.
The solder strip unit is made up on a five terminal strip. The antenna connection is made to the twisted ends of the ceramic capacitors. When soldering the leads of the 1N34 diodes, care must be taken to avoid overheating. Clip a heat sink onto the lead between the diode and the terminal as shown in Figure 12.
It is beyond the scope of this pamphlet to show how to make
but the layout of the board is provided in Figure 13.
Figure 14 shows the front and back view of the completed printed circuit.
A small switch may be installed on the board to activate the zener
This board was designed for use in clocks.
The antenna needs to be of sufficient size to supply the APM with
RF current to cause conduction in the germanium diodes and charge the
coupling capacitors. It has been found that a long horizontal wire
best. It will work better when raised higher.
Usually 20-30 feet is required. Lower elevations will work, but a longer wire may be necessary.
In most location, possible supporting structures already exist. The wire may be stretched between the top of a building and some nearby tree or telephone pole. If live wires are present on the building or pole, care should be taken to keep your antenna and body well clear of these hazards.
To mount the wire, standard commercial insulators may be sued as well as homemade devices. Plastic pipe makes an excellent antenna insulator. Synthetic rope also works very well, and has the advantage of being secured simply by tying a knot. It is convenient to mount a pulley at some elevated point so the antenna wire may be pulled up to it using the rope which doubles as an insulator (Figure 16).
Figure 17 is an illustration of a horizontal wire antenna using a building and tree.
Usually a good ground can be established by connecting a wire to the water or gas pipes of a building. Solder or screw the wire to the APM-2 ground terminal. In buildings with plastic pipes or joints, some other hookup must be used. A metal rod or pipe may be driven into the ground in a shady location where the earth usually is damper. Special copper coated steel rods are made for grounds which have the advantage of good bonding to copper wire. A ground of this type usually is found within the electrical system of most buildings.
Conduit is a convenient ground provided that the conduit is properly grounded. This may be checked with an ohmmeter by testing continuity between the conduit and system ground (ground rod). Just as with the antenna, keep the ground wire away form the hot wires. The APM's ground wire may pass through conduit with other wires but should only be installed by qualified personnel.
Grounding in extremely dry ground can be enhanced by burying some salts around the rod. The slats will increase the conductivity of the ground and also help retain water. More information on this subject may be found in an antenna handbook.
Good luck getting your Ambient Power Module working. It is our hope that experimenters will find new applications and improve the power capabilities of the APM.
Parts List for the APM-2
Four 1N34 germanium diodes ~ Figure 1, X1,
X3, & X4
Two 0.2 mfd 50 V ceramic capacitors ~ Figure 1, C1 & C2
Two 100 mfd 50V electrolytic capacitors ~ Figure 1, C3 & C4
Copper wire for antenna & ground connections
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