Revisiting Classics With Antique Radio Receivers
Radio receivers come in many shapes and sizes, and have many different purposes. There are home radios (the "wireless"), police, fire and ambulance radios, maritime and aviation radio receivers and citizen's band radio, to name but a few. Since radio has been used for many years, and has so many uses, it is not surprising that there is an interest in antique radio equipment, especially antique radio receivers. Early radio receivers were little more than some crude electronics in a wooden box, or even just mounted on a piece of wood. Long before the transistor radio, the components required to make a a radio receiver were coils, crystals and vacuum tubes or valves. Just the components themselves are today items that evoke nostalgia. Add to this a wooden box or Bakelite case and the collectors come scurrying out of the woodwork.
Perhaps the most sought-after items are the Bakelite home radios. Dripping with the styles of the past, these radio receivers were once treasured possessions that are now used as templates for the retro stylings of many modern radio receiver equipment. The material, Bakelite, was used extensively in the early part of the 20th century to create all manner of household items. It was one of the first materials that could be used in mass-produced items without great cost, so it appeared in the home as door handles, electronics casings, telephones, cameras, guitars and all manner of smaller items, from dials to figures and jewelery. Yet for such a common material, there are less than the expected number of surviving items today. Partly this is to do with the culture of disposable belongings that came with mass production, but mostly it is because of the brittle nature of the material itself. These factors, combined with the nostalgia and the telltale odor of Bakelite when rubbed, combine to create an aura of the past that captivates collectors in many fields, especially those interested in antique radio receivers. Almost all of the antique radio receivers are based on AM radio. AM, or amplitude modulation, is a form of radio that has since been mostly made obsolete by FM (frequency modulation). Sound is a wave and EM radiation is wave, so the first thought might be to simply use the sound source as the input to the transmitter. Unfortunately, the frequencies used by transmitters are in the MHz range (millions of cycles per second) while audible sound only reaches up to the KHz range (thousands of cycles per second). With this in mind, it's a simple step to decide that the sound can be encoded as changes in the amplitude of the EM radiation. Now we have a signal (the audio) and a carrier (the EM wave). So, we say that the carrier is modulated in amplitude by the signal - this is AM radio. It is cheap to emit and simple to receive. Today, very simple antique radio receivers, such as the Philmore "super radio crystal set" fetch around 50 dollars, even though it is little more than a single valve, some wire and a small base of Bakelite Larger items, such as the 1925 Grebe "Synchrophase MU1", fetch upwards of 300 dollars. Other items, especially those made rare by fragility and time or high original purchase cost, can fetch thousands of dollars. |
