Radio is the transmission and reception of electromagnetic waves that fall on the radio frequency spectrum, from 30 kHz to 300 GHz. Radio transmitters transform sound into an electrical signal, which then modulates the amplitude (for AM radio) or frequency (for FM radio) of the transmitter’s signal. This modulated signal is sent into the air via an antenna as electromagnetic waves. A radio receiver then picks up frequencies via its own antenna, decodes the signal, and sends it to a speaker, where it is converted into sound waves.
Experts and amateurs who have an interest in building, repairing, or collecting radios have many sources of information, parts, and accessories. In theory, a complete list of radio parts and accessories would be virtually limitless, given the wide range of radios and radio equipment, and the many ways in which radio technology has changed over the years. However, a basic knowledge of the most fundamental elements of a radio help potential buyers interested in buying radio parts and accessories.
One of the most recognisable features of a radio, the antenna is the part that first picks up radio waves out of the air. Antenna switches are also available; they are a convenient way to switch between multiple antenna systems.
Simply put, a capacitor is where the electrical charge is stored. A basic capacitor consists of two conductive capacitor plates or electrodes, separated by an insulating dielectric. However, in some earlier radios, capacitance was low enough that there was no dielectric, but rather a vacuum between the two electrodes. These were called variable capacitors. Later designs contained a polymer foil as insulator between the two plates. In electrolytic capacitors, one of the plates is an electrolyte, or ionic conducting liquid; this type of capacitor is present in tube radios.
In a radio tuner, the capacitor works together with an inductor to act as a resonator, which, by resonating at a particular frequency, is able to pick up one radio frequency out of thousands of signals. The amount of energy a radio capacitor can store is expressed in picoFarads, or Pf. In addition, the voltage that passes across the capacitor is measured.
Capacitor Dielectric Material
Capacitors are generally classified by the material they use for a dielectric, or insulating barrier between the plates. Dielectric material for radio capacitors vary. The following chart outlines the most common materials.
High voltage performance; used in older radios; tendency to absorb water led to its replacement with plastic
Stable; ages well; may not tolerate high temperatures and frequencies
Stable; tolerates high temperatures and voltages; reliable; expensive
Stable; tolerates high temperatures and voltages; reliable; expensive
Compact, inexpensive, and generally good for high-frequencies; capacitance varies; does not last long
Used in electrolytic capacitors
Solid conductive polymer; longer-lasting with lower resistance than electrolytic capacitors; more expensive
Care should be taken when handling older capacitors, which may have self-degraded with lack of use. For example, some electrolytic capacitors can be restored gradually, at low voltage, over a period of 30 minutes, but this may not work for solid-state capacitors. For safety’s sake, always consult an expert to prevent blowing a fuse or other problems.
In radios, inductors act with capacitors to create a resonator, which, by vibrating at one frequency, picks up a certain radio signal from thousands. Inductors are metal coils wrapped around a core. When a current flows through them, they want to build up a magnetic field. When the current ceases, they resist the depletion of energy from their magnetic field. This resistance to change in the flow of current in is inductance, which is measured in henrys (H).
The diode is the part of an AM radio that acts as a detector to decode the frequency signal. Current can flow through a diode in only one direction; the diode thus clips off part of the signal’s sine curve, which is then sent to the amplifier for amplification.
In FM radios, the detector transforms the signal into sound.
In transistor radios, the transistor is a semiconductor through which the charge passes and is amplified. The invention of the transistor in 1947 marked a major advance in radio technology, and electronic devices in general. The first transistor radio, the Regency TR-1, was introduced in 1954, and was an instant success. Transistor radios quickly eclipsed their vacuum tube predecessors.
Before the development of the transistor, valves (also known as vacuum tubes), were used to amplify sound. Comprised of three or more electrodes in a sealed vacuum, the valve is able to control and modulate an electric current passing through it, allowing for amplification of the signal.
Most valves are in glass envelopes, although other materials have been used, including metal, fused quartz, and ceramic. Valve bases are metal pins that connect the valve to external circuitry. Valve caps were used in early models to connect one or two of the internal electrodes, the grid and the anode.
Once the sound is amplified, it is passed to the speakers. The alternating current reaches the speaker’s electromagnetic coil, which is surrounded by a magnet. The current’s alteration causes constant change in the coil’s polarity, which incites attraction and repulsion with the magnet. This in turn causes the coil’s back-and-forth movement, which moves the cone attached to it. Finally, this movement produces sound waves in the air.
After transistors, the discovery of integrated circuits was another advance in electronics. Jack Kilby of Texas Instruments first demonstrated the device in 1958, and later won the Nobel Prize in Physics for his work. Prior to that, circuitry had been constructed of individual components attached to a substrate, whereas integrated circuits are made of one piece of semiconductor material to which the circuitry is attached with metal parts. Because of their compactness, integrated circuits can be used for small radios, as well as a wide range of other electronic equipment.
Voltage regulators regulate the power to car radios. This is particularly important with vintage radios that may not handle higher voltage from more powerful cars. They are generally specified for which vehicle makes and years they are intended.
Manuals and Books
For those who are interested in printed matter connected to radios, there are many choices. Manuals from antique, vintage, and contemporary radios are available. Collectors’ guide books can be an excellent resource for learning more about antique and vintage radios. In addition, there are many magazines, catalogues, and more, dedicated to radio history and technology.
Radio kits contain all the necessary parts to build one’s own radio. Both educational and fun, these kits can be a perfect gift for amateur radio enthusiasts.
Smaller, miscellaneous radio parts are also available, including dials, cables, switches, knobs, and more.
Radios Sold for Parts or Repair
Radio fans can often find contemporary, vintage, and antique radios that no longer function but can be used for parts. Some items may be repaired for use by someone with the appropriate parts and knowledge.
Finding Radio Parts and Accessories
Radio parts and accessories can be found in a variety of places, though most require access to experts, which may not be available locally. If there is a local Radio Enthusiasts’ organisation, they may organise swaps, markets, and radio-related events. While perusing street markets is likely to lead to some radio-related items, dealing with professionals with expertise helps when searching for rare, obscure, or obsolete items. Antique shops may also occasionally have old radios and related printed material.
However, the Internet is probably the best resource for radio lovers. Websites run by amateurs and experts alike can provide valuable information, and auction websites like eBay are a great place to look for parts and accessories; consumers can browse listings from sellers worldwide.
How to Buy Radio Parts and Accessories on eBay
Buying radio parts and accessories on eBay is a straightforward process. Starting from eBay’s home page, enter search terms like “radio valve” in the search bar. You can then modify your search results by price range, seller location, item condition, and more. If you’d like to learn more about searching on eBay, you can visit the Search Tips page.
Steps to Take Before Bidding
First, read the product description carefully, noting details such as item condition, any technical specifications, materials, and quantity. If you’d like more information on the item, you can contact the seller through eBay. Also note shipping costs, which are in addition to what you bid, and the seller’s return policy.
Finally, research the seller by reading feedback from previous customers. It is important to know the seller’s level of expertise, as well as their reliability. Top-rated sellers have a strong record of providing excellent customer service.
Amateur and expert radio enthusiasts alike have a wide selection of radio parts and accessories from which to choose. Antennas both pick up and transmit radio signals in the air, amateur ham radios can benefit from antenna tuners, and switches make it easy to use more than one antenna. Capacitors and inductors work together to act as a resonator, whose resonations at a particular frequency select one radio frequency out of thousands. There are many different capacitor materials available. In AM radios, a diode then decodes the frequency signal; in FM radios, this is done by a detector. The next step is amplification: in earlier models this was performed by valves, which were later replaced by transistors. Once amplified, the sound is sent to speakers, where the electrical current ultimately produces movement and sound waves.
Other items such as voltage regulators, knobs, dials, radio kits, and manuals are also of interest for those building, repairing, or collecting radios. Because radio technology has changed through the years, consumers should inform themselves about radios and radio parts for their particular model before shopping.