Receiving sets in the Twenties.

From Harmsworth's Wireless Encyclopedia.

A receiving set is a piece of apparatus comprising everything necessary to intercept signals, transmitted by wireless and translate them into audible messages.
  It may be a simple or very elaborate apparatus. Its size, type and design are governed by a variety of factors, the first being the purpose for which it is required. For example, one form of receiving set may be needed for high-speed commercial work dealing exclusively with spark signals or the Morse code system. Others are limited to reception of speech and music broadcast from near-by stations.
  The amateur is mostly concerned with the reception of telephony in the form of speech and music. Whatever the nature and purpose of the receiving set, it must comprise certain essential features.
  One is the addition of an energy collector, generally in the form of an aerial and earth connexion, but may consist merely of a few turns of wire on a light wooden framework, then known as a frame aerial or loop. Alternatively the set may work merely with an earth connexion, or even pick up signals with no other energy collector than the wires with which the set itself is wired. Often, however, an exterior aerial is used to collect the energy radiated from the transmitting station. The connexions from the aerial and earth are brought to the receiving set.
  The first requirement in a receiving set is some means for tuning the set to make it capable of dealing with the signals at a particular wave-length on which the particular station which it is desired to hear is working. Common forms of such tuning elements comprise a coil of wire, known as an inductance and the capacity-coupled form of variable or moving condenser. Connexions are then made from the tuning element to the receiving set, to the rectifier or detector. This may either be a crystal or a detector valve. Both perform essentially the same function, to rectify the current pulsations and pass them on to the telephones. These render the electric current pulsations in the set audible to the huamn ear in the form of speech or music, or the familiar buzz of Morse or spark signals.

The McMichael crystal set provides efficient reception inside of a radius of 10 to 15 miles from a broadcasting station.	H.F. or L.F. amplifiers may successfully be used to increase the signal range of the Radio Instruments Co.'s crystal set.
Single valve set by Economic Electric Co., suitable for reception up to 30 miles from the broadcasting station.	Interior of the set above showing tapped inductance and condenser, which form the tuning system of the set.

Tingey two-valve set. Within a reasonable close radius of the broadcasting station this set gives very good loud-speaker results	Fellophone three-valve set. Practically all stations are picked up on the telephones, and near stations can be heard on the loud speaker.
Handsome four-valve cabinet. The Sterling four-valve set is an exceedingly efficient instrument that will bring in all stations in Great Britain.

Climax set and frame aerial. A dual amplification circuit is employed in this most compact instrument.	Three-valve set. The Sterling "Threeflex", employing dual amplification, gives results equal to an ordinary four- or five-valve set.
Climax set packed up. It would be difficult to conceive of any instrument of greater portable utility than this.

Building up a set by units. Various stages of amplification can be added to the detector unit, as in this McMichael set.

To be continued on next page.

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