Old Radio Parts

Introduction

 There are lots of pages of early wireless components in the Virtual Radio Museum. Mostly these are currently jumbled up in groups awaiting sorting out.

Those below were scattered in the back of a neighbour's truck which pulled up at the front gate many years ago (en-route from the local tip) and probably represent the contents of a radio experimentor's "junkbox". There's enough bits and pieces to contruct several decent sized early to mid 20s wireless set, given a set of battery valves, an ebonite front panel and a mahogany box.

As time progresses I shall take decent pictures of these components and add them to these pages.


Selection of condensers...1920's

 

 These are constructed in either bakelite or ebonite cases and amongst the examples shown is included (top centre) an inter-stage type incorporating a grid leak. Condenser manufacturers were competing directly with transformer manufacturers.

Signal amplification could be gained by using a transformer and these were available having various step-up ratios, trading current for voltage. If one had sufficient gain available in the valve itself a much cheaper device was available in the interstage condenser/grid leak component.

I notice there's also a dual condenser at the centre, no doubt cheaper than buying two separate componnets.

Wireless parts were not cheap but were certainly a way of making a radio for a lot less than already fully assembled from the wireless shop.


Coils from the 1920s

 

 Often coils were wound by hand from cotton covered wire as is the centre one.

To improve performance in the days when valves had poor gains it was necessary to get the utmost fron your components. It had been known since around 1900 that in the case of alternating currents very little of the power was conducted in the core of a wire. Nearly all the current travelled in the outer surface of a wire so it was desirable to have as much surface area as possible along which to direct the AC. Litz wire was used in high quality coils. This consisted of many many individually insualated strands of copper wire twisted together. To terminate Litz wire it was necessary to bare the end of every strand and connect these together at both ends of the wire. This ensured a relatively huge surface area to volume ratio compared with ordinary wire. Hence very little loss was to be found in tuning coils made from Litz wire. Thus improved selectivity and sensitivity and considerably increased the reception range and volume obtainable from a wireless set. Another technique commonly employed was a basket-weave method of construction. This reduced the capacity and increased the inductance for a given coil also improving overall performance. The material from which the coil formers was made had an effect on losses and it is common to find expensive materials such as ceramics employed were losses must be minimised, for example in short wave receivers.


Old potentiometers, chokes, old wire and old reaction condensers

 
 

 Variable condensers like these designed for reaction circuits were relatively cheap and did not have to have the same quality as tuning condensers which were air spaced and had to have a linear characteristic ideally matching dial calibration.

 


Old dials, slow motion drives and an old wavechange switch

 

 


A collection of knife switches from around 1928

 

 Earthing switches were used to ground the aerial input to one's house in the event of a thunderstorm. The centre connection went to the aerial feed and the outers to the receiver and to a good earth connection.

An approaching thunderstorm could always be heard on an old radio, unlike todays FM receivers, which are pretty well immune to this sort of thing. Even the modern Long/Medium Wave sets are pretty deaf to lightning noise due to the use of directional internal ferrite rod aerials but with the obligatory 100 foot aerial of the 20s and 30s one could hear lightning at some distance as a series of loud crashing noises. The prudent householder would then throw his Earth Switch, to the safety position, for the duration of the storm.

These examples were made in Liverpool by Ashley Radio.


 

See more old bits and pieces