We found an interesting tip that might just improve the performance of those small affordable handheld ham radios called a “Handy Talky” or HT for short in ham vernacular. [RadioHamGuy] posted an interesting video on adding a counterpoise antenna wire to an HT. He claims it will noticeably improve both transmit and receive by making a quarter-wave monopole into a makeshift dipole antenna system.
Per his instructions you basically add a short wire to the antenna’s outer ground connection or to an equivalent case screw that’s electrically connected to the antenna’s ground side. Apparently this can be referred to as a Tiger Tail and does make it look like your HT has a tail. You would construct a counterpoise antenna wire 11.5 inch for VHF, 6.5 for UHF and about 19.5 inches for an OK performing dual band VHF/UHF radio.
Normally with a handheld radio the counterpoise (ground) is your own body as you are holding the HT. This is because the capacitance of your body makes a good counterpoise under normal conditions. It would be interesting to hear what others find for performance when adding a counterpoise antenna wire.
You can watch [RadioHamGuy’s] full construction tutorial video for multiple radio types after the break.
Continue reading “Improve Your HT Ham Radio by Adding a Counterpoise Antenna Wire”
Radio direction finding and fox hunting can be great fun and is a popular activity with amateur radio (ham radio) enthusiasts. These antennas are great and are not only good for finding transmitters but also will greatly increase directional distance performance including communicating with satellites and the international space station (ISS).
[jcoman] had a nephew who was interested in learning about amateur radio so [jcoman] figured building and using a cheap and portable 2 meter band VHF Yagi style beam antenna would be the perfect activity to captivate the young lad’s interest in the hobby.
His design is based on [Joe Leggio’s] (WB2HOL) design with some of his own calculated alterations. We have seen DIY Yagi antenna designs before but what makes this construction so interesting is that the elements come together using bits of cut metal tape measure sections. These tape measure sections allow the Yagi antenna, which is normally a large and cumbersome device, to be easily stowed in a vehicle or backpack. When the antenna is needed, the tape measure sections naturally unfold and function extremely well with a 7 dB directional gain and can be adjusted to get a 1:1 SWR at any desired 2 m frequency.
The other unique feature is that the antenna can be constructed for under $20 if you actually purchase the materials. The cost would be even less if you salvage an old tape measure. You might even have the PVC pipes, hose clamps and wire lying around making the construction nearly free.
We were quite surprised to find that such a popular antenna construction method using tape measure elements had not yet been featured on Hackaday. For completeness this is not the only DIY tape measure Yagi on Instructables so also check out [FN64’s] 2 m band “Radio Direction Finding Antenna for VHF” and [manuka’s] 70 cm band “433 MHz tape measure UHF antenna” postings. The other Yagi antenna designs featured on Hackaday were “Building a Yagi Uda Antenna” and “Turning an Easter Egg Hunt into a Fox Hunt” but these designs were not so simple to construct nor as cleverly portable.
Lots of readers are into toying around with RF and ham radios. One thing that is always of concern is tuning the antenna. New equipment is never cheap, so whenever another option comes along that uses existing test gear it gets our attention. [Alan Wolke] aka [w2aew] covers a process he uses to tune his HF antenna using a signal generator and oscilloscope.
The process is more of a teaching aid than a practical replacement for commercial equipment mostly because proper signal generators and oscilloscopes are large items and sometimes not available or affordable. That said, if you do have such test gear you only need build a simple breakout board containing a form of wheatstone bridge where the unknown Rx is the antenna. Two oscilloscope probes are connected across the bridge balance nodes. Some special care needs to be taken matching probe cable length and 50 ohm input impedance to the oscilloscope. A couple of 1K probe coupling resistors are also needed to prevent affecting the impendence at the hookup points. Once the selected signal is injected you can adjust an antenna tuner until the two voltage waveforms match on the oscilloscope indicating your antenna network is tuned to 50 ohm impedance with no reactance.
Being able to tune your antenna visually can really help you understand what is going on in the turning process; matching not only input impedance but also phase shift indicating inductive or capacitive reactance. Join us after the break to see the video and for information on what’s presented in the second part of [Alan’s] presentation.
Continue reading “Visually tune your HF antenna using an oscilloscope and signal generator”
We’ve seen our share of commercially available HDTV antennas that work really poorly. For at least four years now we’ve gone without cable television, using a coat hanger antenna we made ourselves to record over-the-air broadcasts. But it’s a pretty ugly beast — we’re lucky enough to have an attic in which it can be hidden. If you’re in need of free television and don’t want an eyesore of a an antenna try building this foil and cardboard version. Even it if doesn’t work at all you’re only out about ten bucks.
The expensive part is the matching transformer which converts screw terminals to a coaxial cable connection so that it may be connected to your HDTV. You’ll need a few nuts and bolts, but we assume you can beg, borrow, or steal the tin foil, cardboard, and glue that round out the parts list. Glue, measure, cut, fold, fasten, finished! You’ll be watching horrible summer TV in no time!
If it doesn’t perform as expected just reuse that connector and try your luck with a fractal antenna.
[Danilo Larizza] is sharing a network connection between a couple of apartments. They are not far apart, but they are also not right next to each other so a set of external antennas is necessary. He built this 2.4 GHz biquad antenna on the cheap (translated) just to test if it improved the signal before he tried to buy a proper antenna. It turns out to work well enough that this is all that he needs.
The antenna itself is about one meter of thick wire bent into two squares which are 31mm on each side. The coaxial cable going to the router connects to the center portion of this antenna. For a bit better directional reception he added some tin foil as a reflector. Since this is outdoors he used a food storage container for protection (the antenna is mounted to the lid, the body has been removed for this picture). The whole things is perched on a stake in a flower pot with proper line of sight to the other antenna.
We’ve seen a very similar design used for an NRF 24L01+ radio. If you need more details that [Danilo] posted that would be a good project to study.
This RC truck can be controlled with the tip of your thumb or the tilt of a wrist. That’s thanks to the IOIO which was inserted in place of the toy’s original controller. [Exanko] made the hardware changes in order to use his Android phone as the controller. The white circle is a software joystick that acts as throttle when your thumb moves along the Y axis, and steering when it moves along the X axis. But while he was at it he also included accelerometer input as an alternative control option.
The IOIO board has a Bluetooth dongle connected to its USB port as a means of wireless communication. The dongle was hacked to accept an external antenna, thereby increasing the truck’s range. There is also some on-board flair like LEDs for lights and even a laser diode for… well we’re not sure what that’s for. Get a better look at the hardware internals in the clip after the break.
Continue reading “IOIO controller replacement for an RC truck”
We can’t wait to give this one a try. We’ve got a DIY HDTV antenna hanging out in the attic which was made from some scrap wood and eight metal coat hangers. It works great but it’s pretty ugly and not everyone has an attic to hide it in (not to mention the signal drop caused by the roof shingles). This is a fractal antenna anchored to some clear plastic so you can just hang it in the window and start picking up the over-the-air channels without much effort.
The pattern was modeled in SketchUp then printed out on two pieces of paper. One piece had it printed on both sides, which makes it easy to glue on a sheet of aluminum foil, then follow the pattern on the opposite side to cut out the important parts. The other template was used as an aligment guide when gluing the foil to the clear plastic. A coaxial adapter was then attached using nuts and machine screws. If you build it, let us know how it comes out!