PVC Fig Rig

pvc_fig_rigThis is my version of a project I found here that aims to mimic the so-called “Fig Rig” created by the film director Mike Figgis (Leaving Las Vegas). Made from PVC pipe for around $30, it is much more economical than the retail version which sells for around $300.

The whole idea of this device is to allow your arms to act as shock absorbers, creating a poor man’s steady-cam for use with a hand held video or still camera. I painted mine flat black to disguise the look of the PVC. To paint the plastic I had to use special plastic spray primer before applying the finish coats of regular spray paint. While I don’t have a true video camera, this is a fun project to use with a regular digital camera since most of the newer still cameras also take fairly good quality video.

Vacuum Tube Audio Amplifier

tube_amp1tube_amp2I have been somewhat interested in vacuum tube projects for awhile now after I refurbished an old AM radio from my grandmothers house. Although a simple project, involving cleaning the radio and replacing the old tubes with new ones, I think the main draw of a tube project is that distinct retro feeling you get when you fire up the project and it starts glowing, but in a good way. While looking around for a simple, beginners tube project I stumbled upon a fairly large community of people who had built and subsequently modded the K-502 audio amp kit from Antique Electronic Supply.

I purchased the kit and built it in a couple of hours. It is a very simple project to complete, consisting of only about two dozen parts. I had originally planned to assemble the kit in an enclosure, but my final assembly behaved poorly (I think in part due to improper grounding). I reassembled the parts on the pine board which comes with the kit and it now performs flawlessly. The amp takes a standard left and right RCA style audio input and can output up to 8 Watts of power. This may not seem like much, but with efficient speakers it gets loud enough for any common usage around the house.

I would still like to put some sort of cover over the board to minimize the risk of myself or others from coming into contact with the line voltages present. Although not the most inexpensive kit out there (compared to some solid-state kits), it is cheap compared to other tube based audio amplifier kits which can run upwards of $300. Definitely a fun project, especially if you need an extra audio amplifier.

Analog Synthesizer

synthesizer2synthesizer3I have been interested in synthesizers since I first started becoming interested in acid/new wave rock when I was in middle school. Analog synthesizers particularly interested me because they are easier to build and also cheaper, as well as having a lot of nostalgia for the original form of sound synthesis. Consequently when if first ran across the circuit board being offered at Music From Outer Space, I was very excited. The board is not only relatively inexpensive, it is also well made and was shipped very quickly. My synthesizer, pictured below, cost around $100 to make because I had to purchase the majority of the parts as well as the case. I purchased most of the parts and the case from Mouser, except for the potentiometers and the switches which I bought from Jameco. The construction of the board was fairly straight forward and took a few hours. The wiring of the board to the faceplate, however, took several ours of tedious wiring which I would not relish to repeat. In the end though I ended up with a great little unit which works great and can produce a variety of sounds. As can be seen from the photos, I also installed the mod which allows the modulation of VCO-1 with VCO-2’s output. I rearranged the faceplate accordingly to fit on my case’s aluminum plate. I had no alignment issues with the unit and it worked from the first time I turned it on. In the future I may build an audio amplifier as well as a sequencer to control the oscillators and actually produce music as opposed to just noises.

synthesizer4I had been looking for some time for a way to modify my analog synthesizer project to be powered by an AC adapter instead of the two 9 volt batteries that it had originally been designed to use. This was more complicated than it sounds since the synthesizer requires both +9V and -9V from the same power supply. After some investigation I found a circuit; that could be used to transform a single +9V input into both +9V and -9V. It is a really clever design that accomplishes this feat using a special charge pump converter IC and a couple of capacitors. As the pictures show I also changed the power switch to one that is more aesthetically pleasing than the toggle switch used previously. I also added a coaxial power socket to the back panel to accept the plug from that AC adapter. The synthesizer performs the same as it did before my modifications, however, I am now freed from having to worry about battery life.

20 meter Groundplane

groundplane1Most hams are familiar with the quarter wavelength ground-plane antenna design. It is often the first antenna they buy or build for use on 2 meters after receiving their technician license. It is a design that performs well and exhibits low input impedance, making it ideal for use with ham equipment without the need for special matching techniques. The antenna is easy to construct and due to this simplicity is also highly economical. When considering the type of antenna to build for field day to use with my PSK31 setup this design was the obvious choice. It provides both low take-off angle and omni-directional radiation, allowing me to maximize my operating capability from a simple station. The antenna is made up of a single pole which supports the radiating vertical element and is guyed in place with nylon rope. The two radial elements are spread out and held in place by ropes.

groundplane2The base of the support pole is made of a ten foot piece of 1.25 inch schedule 40 PVC pipe that was cut in half for easier transport in my car. It is joined in the center by a 1.25 inch PVC coupler. Mounted on top of the PVC pipe is a 13 foot extendable fiberglass fishing rod which I purchased at Gander Mountain (I had originally planned on using a 16 foot rod but none were available when I went to the store, with additional height the radials can be lowered at a steeper angle which in turn raises the input impedance closer to the desired 50 ohms). I joined the fishing rod to the pipe by first removing some of the plastic at the base of the fishing rod so that it could slip inside the pipe. Next I drilled a single hole through the pipe and rod so that I could secure the two pieces together using a small bolt and nut to prevent the rod from sliding further into the pipe. I also wrapped the fishing rod with some electrical tape to compensate for the difference in diameter of the rod itself and its plastic base (this allows the rod to fit snugly inside the PVC pipe thereby stiffening the rod and pipe connection).

groundplane3groundplane4The radiating element and both radials are 16.5 foot long 14 AWG insulated stranded copper wire. For ease of assembly I soldered the radiating element to the center of a SO-239 connector and attached solder lugs to the radials. This allows me to attach the radials to the SO-239 with two small bolts passed through the holes on the connector, simplifying construction in the field. I taped the radiating element to the pole prior to raising the antenna. The radials were attached after the antenna was erected and securely guyed since the feed point is only 5 feet off the ground providing easy access for mounting. From start to finish assembling the antenna and guying it in place took about 30 minutes to do by myself (with more people it could easily be erected in 5-10 minutes).

The performance of this antenna was better than expected. It matched perfectly on the lower end of 20 meters despite being cut for the center of the band (this is due to my use of insulated wire which adds capacitive loading to the antenna, electrically lengthening it). Whether you are looking for a solid performing base antenna or a light, compact, portable antenna this may be the project for you.

PSK31 Sound Card Interface

psk_interfaceIf your sound card has Line In and Line Out jacks, and your radio has an accessory port, this is the easiest way to interface between the two. Using your radio’s accessory port eliminates the need for more circuitry to control the audio level going to and from your radio. This interface has worked perfectly during regular use and several Field Days. All the parts are available from RadioShack, and it can be constructed in under an hour.

Shortwave Regenerative Receiver

regen2regen1This project is a great way for beginning builders to hone their skills at circuit construction. The receiver plans were originally printed in a September 2000 article in QST. I built mine from scratch, not on a printed circuit board, with no ill effects due to strange parts placement. The author provides very good advice about the audio/volume and regeneration controls placement and hookup (by being careful, no shielded audio cables are necessary). Since I used a large value tuning capacitor from my junk box, I added the optional fine tuning control to add better selectivity to my receiver, which is very helpful when tuning. By following the author’s recommendations about how to assemble the receiver the average builder should have no problems with this project. When in doubt, the provided voltages on the schematic are a handy way to test your completed project.

2 Meter J-Pole Antenna

jpoleThis is perhaps the cheapest gain antenna for 2 meters that can be built. Total cost for this antenna is under $10 (excluding coax) and it can be built in about an hour. Using what is called “Plumber’s Delight” construction I soldered all joints using a propane torch, lead-free/non acid core solder, and some soldering flux. While there are several iterations of the J-Pole that can be built, I liked this one because it does not require the builder to directly solder the coax to the copper pipe. Instead, a SO-239 is soldered to the T connector and a short piece of wire (I used insulated #12 stranded copper) is soldered to the center conductor to feed the driven element. My version of this antenna is mounted on my chimney and works very well, providing 2:1 or better SWR on the entire 2 meter band. It is incredibly strong and I have experienced no problems with wind or other weather.