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An antique radio is a radio receiving set that is collectible because of its age and uniqueness. Although collectors may differ on the cutoff dates, most would use 50 years old, or the pre-World War II Era, for vacuum tube sets and the first five years of transistor sets.

Types of antique radio

Morse only sets
The first radio receivers used a coherer and sounding board, and were only able to receive morse code, and thump it out on the board. This type of transmission is called CW (Continuous wave) or wireless telegraphy. When wireless telephony (ie transmission & reception of speech) became possible, speech radio greatly improved the usability of radio communication. Despite this, the antiquated technology of morse code transmission continued to play an essential role in radio comms until the 1990s.
The idea of radio as entertainment took off in 1920, and radio ownership steadily gained in popularity as the years passed. Radio sets from before 1920 are rarities.
Pre-war sets were usually made on wooden breadboards, in small cupboard style cabinets, or sometimes on an open sheet metal chassis. Homemade sets remained a strong sector of radio production until after the war. Until then there were more homemade sets in use than commercial sets.

Early sets used any of the following technologies:
- Crystal set
- Crystal set with carbon or mechanical amplifier
- Basic TRF
- TRF Reaction Sets
- Super-Regenerative Receiver
- Superhet

Crystal sets
These basic radios used no battery, had no amplification and could only operate headphones. They would only receive very strong signals from a local station. They were popular among the less wealthy due to their low build cost and zero run cost. Crystal sets had minimal ability to separate stations, and where more than one high power station was present, inability to receive one without the other was a common problem.
Some crystal sets users added a carbon amplifier or a mechanical turntable amplifier to give enough output to operate a speaker. Some even used a flame amplifier.

TRF
TRF sets (Tuned Radio Frequency) are the most popular class of early radio. These used one or more valves (tubes) to provide amplification. Early TRF sets only operated headphones, but by the 1930s it was more common to use additional amplification to power a loudspeaker, despite the expense.
The types of speakers in use at the time were crude by today's standards, and the sound quality produced from the speakers used on such sets is sometimes described as torturous. Speakers widely used on TRF sets included:
- moving iron horn speakers
- moving iron cone speakers
- tin can, magnet & wire based speakers
- in a few cases a moving coil speaker

The above are not altogether clear distinct categories, with significant overlap, nor a complete list, but represent the technologies in popular use.
Earliest TRF sets used no regeneration, and had very poor rf sensitivity and low selectivity. Thus only nearby stations and strong distant stations would be received, and separating different stations was not always possible.
Most TRF sets were reaction sets, aka regenerative receivers. These rely on positive feedback to achieve adequate gain. This approach worked well enough, but is inherently unstable, and was prone to various problems. Consequently there was a significant amount of hostility over maladjusted radios transmitting squealing noises and blocking reception on nearby properties.
TRF sets had typically 2 tuning knobs and a reaction adjustment, all of which had to be set correctly to receive a station. Earlier reaction sets also had filament adjustment rheostats for each valve, and again settings had to be right to achieve reception.

Superhets
In this era of early radio, only the wealthy could afford to build a superhet. Such sets required many valves and numerous components, and building one was a sizeable project.
Pre-war superhets were often used with the relatively expensive moving coil speakers, which offer a quality of sound unavailable from moving iron speakers.
Most post-war commercial radios were superhets, and this technology is still in widespread use in consumer radios today, albeit implemented with transistors and ICs.

The advantages of superhets are:
- Excellent sensitivity, enabling reception of foreign broadcasts
- Complete stability
- Well controlled bandwidth
- Well shaped rf passband avoids the uncontrolled tone variations of TRF sets, and gives good selectivity

The downsides for pre-war superhets were:
- Very high build cost
- High run cost due to many valves and the need for large high power batteries
- Construction was a sizeable project

Foxhole radios
World War 2 created widespread urgent need for radio communication, and foxhole sets were built by people without access to traditional radio parts. A foxhole radio is an illegally constructed set from whatever parts one could make, which were very few indeed. Such a set typically used lighting flex for an aerial, a razor blade for a detector, and a tin can, magnet and some wire for an earpiece. I.e. they were crude crystal sets.

Wooden consoles
The console radio was the center piece of every house back in the era of radio, they were big and expensive running up to $700 back in the late 1930s. Mostly for the wealthy, these radios were placed in hallways and living rooms. Most console radios were waist high and not very wide, as the years went on they got shorter and wider. Most consumer console radios were made by RCA, Philco, General Electric, Wards Airline, Montgomery Ward, Westinghouse, radio-bar and many more. Brands such as Zenith, Scott, Atwater-Kent, were mainly for the rich as their prices ran into the $500-$800 range in the 1930s and 1940s.

Table top radios came in many forms:
- "Cathedral style", an upright rectangular box with a rounded top
- "Tombstone style" were rectangular boxes that were tall and narrow like a tombstone
- "Table top" were rectangular, with width being the larger dimension. Table top radios were usually placed in the kitchen, sitting room or bedroom, and sometimes used out on the porch.

Bakelite
The availability of the first mass produced plastic Bakelite allowed designers much more creativity in cabinet styling, and significantly reduced costs. However, Bakelite is a brittle plastic, and dropping a radio could easily break the case. Bakelite is a brown-black mouldable thermosetting plastic, and is still used in some products today.

In the 1930s some radios were manufactured using Catalin, a colourable version of bakelite, but nearly all historic bakelite radios are the standard black-brown bakelite colour.

Plastic era
The affordability of more modern light coloured thermoplastics in the 1950s made brighter designs practical. Some of these thermoplastics are slightly translucent.

Early transistor radios
The invention of the transistor made it possible to produce small portable radios that did not need a warm-up time, and ran on much smaller batteries. They were convenient and chic, though the prices were high and the sound quality not so good.
Transistor radios were available in many sizes from console to table-top to matchbox. Transistors are still used in today's radios, though the IC (integrated circuit) containing a large number of transistors has surpassed the use of singly packed transistors for the majority of radio circuitry.
Transistor radios appeared on the market in 1949, but at a high price. By the 1960s, reduced prices and the desire for portability made them very popular.
There was something of a marketing war over the number of transistors sets contained, with many models named after this number. Some sets even had non-functional reject transistors soldered to the circuit board, doing absolutely nothing, so the sales pitch could advertise a higher number of transistors.

Vacuum tube radios and early transistor radios were hand assembled. Today radios are designed with the assistance of computers and manufactured with much greater use of machinery.
Today's radios are usually uneconomic to repair because mass production and technological improvements in numerous areas have made them so cheap to buy, while the cost of human labour and workshop overheads have not fallen in real terms.

Car radios
Pre-war car radios were experimental only. They required a large aerial, reception was inconsistent, they required adjustment in use, which was not very practical. And they were of course not the most useful place to put an expensive radio.
All early car radios used a vibrator power supply to step up the low voltage to HT for the valves. Vibrator supplies are known for reliability issues, and produce radio interference and some mechanical noise.
Later car radios used valves that ran on 12v HT, eliminating the vibrator.
The 3rd generation of car radios were valve sets with a single output transistor, and makers were very keen to promote these as transistor sets. Some historic car radios badged as transistorised are in reality these hybrid valve sets.
All-transistor sets eventually took over from valves as prices fell.

Warm-up time
Most valve sets needed many seconds for the valves to heat up, though there were exceptions. Warm-up times changed as valves went through several generations of design.
- Bright emitter valves universal in the early 1920s came on in a small fraction of a second, effectively instantly.
- Direct dull emitters typical of the late '20s and 1930s came on in around a second. This type of valve continued to be popular in battery sets for several decades more.
- Indirect emitters used in more or less all mains valve radios from the late 1930s onward were slow to reach emission temperature, with wait times routinely exceeding 10 seconds.
- The last generation of valves was nuvistors. These tiny devices reached emission temperature fairly quickly.

Valuation
In terms of financial valuation:
- Catalin plastic radios and high end console radios sell at the top of the market.
- Cathedrals, tombstones and large table tops are midrange
- wood/bakelite table tops are in the lower mass production bracket and often sell for less than $40 each.
- The valuation of 1920s and 1930s sets depends primarily on condition and appearance. Well presented breadboard sets command a high price tag, but tatty or uninspiring samples don't. Although fairly rare, the difficulties in using such sets affect their sale value.