Miniature Antenna Tower Model with 4 Element Yagi-Uda and blinking lights.
Pulsar Profix: Green TRF, Toner Transfer Sheets
Fiberglass board 0.032″ thick double sided copper clad board
Copper wire #18 AWG
Magnet wire #30 AWG
Copper clad steel wire #14 AWG
Ferric Chloride – Radio Shack
Liquid Tin – Mouser
Sharpie permanent marker
82k, 33k, 1k ohm resistors
NTE 123AP NPN BJT transistor (2N3904)
Red surface mount LEDs
SPST mini toggle switch – Radio Shack
Miscellaneous screws and wire
Lots of solder
1 dead 9 V battery
1 good 9 V battery
Brass screws, washers, and nuts
Video clip of the tower’s blinking lights. Note, sound was purposefully removed from the video. Download FLV
Upper Left – Copper clad fiberglass board; Middle – Toner transfer sheets with etching patterns; Right – Triangular wire tower; Lower Left – Yagi-Uda made of copper clad steel wire. The patterns for the etch resist were designed in AutoCAD. The component designs were based on the symbols in the ARRL hand book.
The vertical parts of the structure are 14 AWG copper clad steel wire . The zigzag structure was made by wrapping 18 AWG copper wire around a flat strip of steel, and then stretching the “coil” out so that it resembles the zigzag structure of a real tower. After making three vertical pieces and three zigzag pieces these were soldered together. The soldering of these was a little tricky… I soldered one vertical and one zigzag piece so that I had three parts to work with. Then carefully tacked two together, and then tacked the third. Once they were tacked in an acceptable manner, the rest of the joints were fully soldered. The “thrust bearing plate” and “rotator plate” were made from small bits of PC board and a couple small coils of copper wire. The Yagi-Uda antenna was made from 14 AWG copper clad steel wire.
Unfortunately I didn’t take any pictures of the etching process. I did have some trouble getting the toner to adhere to the boards at first because the first boards were about twice as thick (0.064″) and had a very hard time running through the laminator. Boards were etched using the “Contact Etch” process detailed at puslarprofix.com. This turned out to be a very fast and high quality way to etch the boards.
After all of the etching, the toner/TRF/sharpie was removed using acetone. Unfortunately when I cleaned the active component board the green TRF got smudged into the fiberglass board. Fully submerging the board and gently rubbing off the toner/TRF/sharpie worked much better. Then all of the copper parts were tin plated using MG Chemicals’ “Liquid Tin.”
After tinning all of the copper clad parts the boards were soldered together on the inside of the box. This was pretty easy, it just used a lot of solder, which meant there was lots of solder smoke and left over rosin. The rosin was cleaned up with acetone.
555 calculations used for component selection
Frequency = 1.44/((R1 + 2*R2)*C1) = 1.44((82k + 2*33k)*47uF) = 0.207Hz or one cycle every 4.83 seconds
t1(time off) = 0.693*(R1 + R2)*C1 = 0.693*(82k + 33k)*47uF = 3.746 seconds
t2(time on) = 0.693*R2*C1 = 0.693*33k*47uF = 1.075 seconds
See video to get an idea of what the flashing looks like. I considered adding more components to simulate the gradual fade in/out of an incandescent light bulb, but decided against it after prototyping the the basic 555 circuit.
Pin 3 (output) is connected to a 1kohm resistor which is connected to the base pin of the transistor(123AP). The emitter pin of the transistor is connected to ground (0V). The collector pin is connected to a 330ohm resistor, which is connected to 9 V. The collector pin is also connected to the anode end of the LEDs while the cathode end is connected to ground.
In this case the LEDs were mounted to a very small bit of copper clad board, this was soldered to the tower on the cathode end. I ran a bit of magnet wire inside the tower to connect to the anode ends of the LEDs.
The circuit board material is pretty thin so the long sides curve in a bit. This wasn’t bad as it made the fit between the box and the base tight. I soldered some copper clad steel wires near the tower legs to add stability.
Active component side. Component symbols as follows: triode, P-channel MOSFET, pentode, NPN Bipolar Junction Transistor, bridge rectifier, diode. The green smudges are from not removing the toner/TRF/sharpie correctly
Passive component side. Component symbols as follows: resistor, iron core transformer, morse key / momentary switch, inductor, crystal, battery / dc power source, electrolytic capacitor, antenna, ground connection.
I used Google SketchUp to help design the wooden base after the box was built. The wooden base is made of two main pieces. The yellow cylinders are brass bolts that secure the box to the base. Since the battery is inside the box, holes were drilled for the ON/OFF switch’s wiring.
To secure the box to the base, the brass nuts were soldered to small pieces of PCB which were then soldered to the inside of the box. Unfortunately I didn’t take any pictures of the base’s construction.