Ham Radio Stuff

This page is an introduction to some interesting topics in amateur and experimental radio. Modern radios factor design and construction into hardware and software components or modules to permit customization without physical hardware changes. PC controlled and software-defined radios also allow internet linking. Low frequency radios are used to monitor frequencies below the AM broadcast band (ie below 540 kHz). QRP radio (ie low power) kits offer an inexpensive way to become an active ham by building your own equipment and operating on-air. Electronic devices using microcontrollers allow rapid design changes and require few components.

PC Controlled Radio

PC controlled radios allow redesign of a radio's user interface without changing hardware. They can also be linked into the web for remote access using sites like GlobalTuners. Some examples of PC controlled radios are:

• TenTec RX320D is a DRM ready 100kHz-30MHz, $370 receiver. [WIKI].
  Control Panels: GNRX320, Radio 320, rxPlus, rxWings, SWLog/RCS, WorldStation, Hardware Panel
• Icom PCR 1000, 1500, 2500 are 10kHz-3.3GHz, $600+ receivers.
  Control Panels: Listing of software UIs, Hardware Panel
• AOR AR2300 is a 40kHz-3.15GHz, $3,700 receiver.

Software-Defined Radio

Software-defined radios can customize the user interface, add features such as frequency analyzers and speech processors or include new modes such as spread spectrum using software changes with minimal or no hardware modification. Most SDR hardware modules use direct conversion (DDS lo) and quadrature sampling [Ref 1] , [Ref 2] techniques. Check YU1LM and openhpsdr.org for active projects. An interesting use is allowing multi-user web access to a receiver such as the site at WebSDR. Wikipedia provides a growing list of SDR products. Some examples are:

Computer requirements vary with software but all require USB ports and a stereo sound card.

Caution: All USB ports are not equal. Older PCs can have USB1 at front ports and USB2 at rear ports. USB1 has lower specs and may not recognize all devices! This seems to cause the most difficulties when using Vista.

Caution: Not all sound cards are stereo. Check before installing software. 24 bit, 96kHz units are recommended!

Low Frequency Radio

Low frequency radios tune frequencies below the AM broadcast band (ie below 540 kHz). These frequencies are occupied by European broadcasters, beacons (location and propagation), time signal and utility stations. Natural radio phenomena (eg whistlers) and sudden ionospheric disturbances (useful to astronomers monitoring sunspots) can also be detected. There are several challenges when monitoring frequencies below 500 kHz. The challenges include equipment availability, effective antennas, noise suppression and verifying what was heard.

Receivers can be expensive but not if compromise is acceptable or one is willing to modify older equipment.

• Recent: Icom R75, TenTec 1254 [kit], Yaesu VR5000
• Older: Japan Radio NRD-5x5, Drake R7
• Alternate: PC controlled radios, SDR radios, up-converters (eg lfEngineering L-111 PCB)
• Customized: UKRAA,

Antennas can be random length, horizontal dipoles, verticals, loops (capable of nulling noise). Preamplifiers are often used. Indoor antennas (eg lfEngineering L400B and MFJ 1020C/1022/1024) are also good solutions.

QRP Radio

QRP radios are low-powered, typically under 5 watts output. This is one area where kit construction geeks and homebrew artists can still have a ball in.

Microcontrollers

Microcontrollers (PICs) are everywhere in today's technology. From a radio enthusiast's perspective they can be used to build keyers, wattmeters, voltmeters, battery charger control systems, and antenna tuners. Hams have had much success using PICAXE units because they have an onboard programming language that reduces the amount of development tools needed in the lab. For programming examples visit TCA magazine and search for PicAxe. Other suitable simple PICs include Arduino and BASIC Stamp.