A Second Attempt at a Really Tiny Bug
The NanoBug II - A QRP Companion
This little bug is another attempt to make a very small bug that is easily portable while being fully functional. It follows a number of MicroBugs and TinyBugs, as well as the first NanoBug, which made its YouTube debut this spring. The small size of this bug is achieved by eliminating the long pendulum and its sliding weight. Instead, it uses a vertical pendulum pivoted about its center of gravity. Motion of the pendulum is controlled by a system of rare-earth permanent magnets. This arrangement makes the bug quite insensitive to changes in position and level.
The speed is controlled by varying the magnetic field; a range of 7 to 30 words per minute is possible, and the duty cycle (dot-weight) is also adjustable. It is build entirely of brass, with stainless steel hardware, and it weighs about 14 ounces. This is enough weight to keep it steady during operation, but it is still light enough to carry into the field for QRP operation.
Dots are generated by the action of a pendulum magnet acting on a magnetic reed switch, and connection to the keyed circuit is made via a miniature phone jack.
The pictures below, reading clockwise from the upper left, show stages in the construction and assembly.
Upper Left – Here are the brass parts, machined and polished, waiting for their lacquer coating. In order to insure proper electrical conductivity, the key is partially assembled prior to applying the spray lacquer. Upper Right – The parts of the driving lever, prior to assembly. This key is a single-lever design with a ball-bearing pivot. Silver contacts on the lever work against the stainless steel adjustment screws to determine the paddle travel, electrical contact, and the weight of the dots in a string. Lower Left – The parts of the base are laid out prior to assembly. It is made of a number of pieces to allow sufficient room for the lower portion of the pendulum. The dot and dash contact pillars attach to the side rails near the front of the key. Lower Right – The symmetrical pendulum and its bearing assembly. The driving magnet is at the top of the picture, while the reed-switch magnet is at the bottom. While the pendulum is symmetrical overall, no attempt has been made to make it balance perfectly. The reed switch is mounted in an adjustable brass tube in the base of the key.
The views below show the major subassemblies during the final stages of construction.
Upper Left - The driving lever has the fingerpieces at one end and the driver magnet in the threaded holder at the other end. The strength of the field will be varied by moving the magnet in or out. Silver contacts are on either side of the magnet end of the lever. Upper Right - The base of the key holds the lever bearings, the contact adjustments, and the electricfal wiring. Lower Left - The pendulum, which is symmetrical about its center, is balanced to offset the effects of gravity. The teflon ball at the rear of the key is part of a detent system to provide centering between the dot and dash movements. The major restoring force is supplied by a pair of magnets (not visible) that provide an adjustable resistance to the paddle movement. Lower Right - The key is ready for the final assembly. Note the top plate, which provides additional support for the pendulum mounting.
Here are some views of the finished key.
A final picture will put the NanoBug II in perspective. While it doesn't pretend to be a Vibroplex, it does a good job despite its size, it likes to go camping and traveling a lot more than its bigger friend.
Listen for it on the air (20 and 40 Meter QRP frequencies), and stay tuned for a YouTube video that will be coming soon.