From the age of twelve, electronics fascinated me. It started with school projects, a crystal radio and also a self made electric motor.
At that time there were no personal computers and radio receivers were either valve based or discrete germanium semiconductor based. My father had one of the first Barlow Wadley short wave receivers. He never used it as I would spend many nights in bed listening to the short and medium wave transmitters. Built an external long wire antenna for better reception, and the fascination for electro magnetic waves was born.
Getting an Amateur Radio License was the obvious next step. During my further education, built UHF and VHF yagi arrays and bounced signals of the moon as well as aircraft flying between Cape Town and Johannesburg, the later was doppler shift hell. Became member of HAMNET and had great times with Metro Response in simulated drills and exercises regarding disasters. Implemented packet radio (pacrat) in my vehicle and used VHF to connect a computer in the car to a network at home (1989).
Many years have passed and everything has changed. Recently picked up 'the hobby' again, and this is where I'm at..
Software defined radio, RF preamplifier's and RF mixers. Adventures into electro magnetic receivers, transmitters and antennas. Showing that when theory states that theory and practice are the same, practice shows this is not always true when working with UHF (Ultra High Frequencies) and beyond this spectrum.
I'll be working mostly in the UHF band (Ultra High Frequency) and irrespective of what you read on Internet about the length of antennas...yes! length is critical, so do not be fooled by antenna parameters unless you are sure they apply to the frequency you require. The alternative is to use a coat hanger or even a pencil, the results will be about the same, but something is better than nothing and not tryings, right?.
Phase I: Antennas for 1090.000 MHz. Goal: Construct, test and compare various antenna designs against a 'tried and trusted' 1/4 wave dipole. Check the results...each have their pros and cons.
More information about the SDR virtual radar setup can be found at ADS-B project and a live view of the virtual radar in operation is available at Virtual Radar Live.
Simultaneous trial testing with different antenna designs. Using the Raspberry PI as software defined radio receiver and data decoder. Initial tests show the PI B+ and PI 2 to be acceptably stable for lengthy trial runs while collecting data.
Antenna types 1/4 wave and J-pole construction explained. The first trial tests between two types of antenna designs includes explanation about basic antenna design. A good place start if you want to know how antennas work.
'What if I tried this' collinear antenna abstraction and other 'oh well there goes the theory' antenna constructions. Some still have me baffled at present. Everything UHF and above is partially 'black science'. PS: Wave guides are out of scope.
The 'trusty' 1/4 wave antenna. Easy to make, the most basic in theory and works perfectly in practice also. It has no gain, but is the perfect control subject for what is to follow. Find out how to construct a 1/4 wave antenna guaranteed to function as required.
Frequency to wavelength antenna design calculators for several popular (tried and tested) antenna designs.
See the Antenna Design Calculator
for more details.
Antenna designs ideally suited for weatherproofing by their slim design so they can easily be mounted in PCV tubing and placed outdoors preventing corrosion and damage from the elements.
Tips and tricks invented to help in testing prototype antenna constructions. From easy variable matching stub connection specifications to the effects of foreign housings, casings and mounts.
Getting the antenna from the state of working prototype to a fully functional industrial design. Confirming the functionality by building the first operational version and the subtle tweaking.
Preparing the antennas for being mounted on masts. Weather proofing and fixture construction so that it is capable of operating in all weather conditions.
A microcontroller based call sign Morse code generator small enough to fit into a hand microphone. Also handy for repeater systems that need to identify on a regular basis. Mixes the audio with any other audio present at time of transmission.
Microcontroller managed tiny high power telemetry transceiver used to track birds of prey or other wild life on the move.
Monitoring aircraft location in real time via a local software defined radio receiver and antenna, and projecting this on a real time map.
Constructing a balun for a QRP EndFed antenna for WSPR, "Weak Signal Propagation Reporter" operations
An easy way to determine the exact best matching point for optimum coupling with receivers and transmitters...
Is using a construction that is adaptable, so that adjustments can easily be made for optimal resonance and performance...
Having suitable measuring equipment (as budget allows) is (really) important. Getting impedance and matching right is crucial to top performance.
The hobby space, after a good day of experimenting and testing (when time allows). And then rest and relaxation.