Geoff's Crystal Sets – Page 2

Heart of Oak Crystal Receiver

Please click on the photographs for a larger picture of this beautiful wireless receiver.
Heart of Oak Crystal Radio

Order Nr. Heart of Oak Crystal Radio

I made this set in 2010 with two intentions in mind one was to go portable with it for use on holidays in the caravan or on camping field days with the ham radio station and a telescopic mast and dipole aerial. The other use was as a test receiver for various components and coils. The main coil and AF Choke coils are plugable. This was again a 'Mystery Crystal Radio' circuit so the main coil has four connections on the base . The Box was made from solid English Oak with comb jointed corners. This was the usual traditional form that the early set makers used in their box construction. It is a very strong box and also was designed to house the headphones and a couple of spare coils in the separate compartment. I intended to make a handle from a piece of Natural Veg leather which would be double handstitched to give it some extra strength.This set is still an ongoing project and I may fit brass edge trim to the box corners at a later date. I will put a tuning scale chart into the lid calibrated in frequency against the 0-100 logging scale.

This set was used at the 'Tate Britain' exhibition 'Restless Times' in which I exhibited a number of crystal sets in September 2011 and the set was really the main one used in the demonstration of sounds from a crystal radio in the 'Duveen Gallery' exhibition

Heart of Oak Crystal Radio Closeup View

Jules Verne Mk. 2

Jules Verne Crystal Radio Mk2

Jules Verne Crystal Radio Mk2

Jules Verne Crystal Radio Mk2  
Jules Verne Crystal Radio Mk2

Dual Slider with Perikon Detector

Dual slider crystal radio with Perikon Detector
If you could fall in love with your electro mechanical creations like your own offspring then this radio comes close.

Beauty simplicity and purity are the words that come to mind when this project was completed.The idea was born when I was contacted by Julian Oliver Artist and Curator for his exhibition at the Phoenix Art Complex in Leicester . He gave me an outline of what he wanted. A set from the origins of radio and around the WW1 period for his project to do with the evolution and origins of modern communications in warfare. He suggested a dual slider however this was not exactly as the military time period for the WW1 but a little later and probably was designed for the commercial radio broadcasting era supported in the UK by the BBC in the early 1920's. However it was a visually appropriate balance of design from around the time period. The Military Crystal receivers were quite complex even in WW1 with military tuning capacitors and many switched coils not available in mass production for commercial receivers at the time. It would be impossible for me to reproduce for this exhibition in the very short time scale of a coupe of weeks that I had to complete the set.So I started the project and burnt the midnight oil on this one. It turned out lucky for Julian and I was able to find a really nice piece of Zincite on eBay with just the right properties that I was looking for, ie a reddish orange crystal with a point for the 'Perikon Detector' a bit more about the detector later.

The principle behind the operation of a 'Dual Slider crystal radios is rather simple in concept as it is just a coil of large inductance in this case 1000µH. Tuning is done by sliding a contact along the coil and this tunes in the station at some point along the coil. Tuning is quite broad but together with the earthy side slider tuning can be made sharper . There is no tuning capacitor to resonate the circuit other than stray capacitance from each winding and the interaction of the length of aerial to the gound or the set itself, at least that is the theory but these radio are strange and have an almost magical feel about them. Make the aerial longer or shorter and the point of tuning on the coil is different. It is beautifully simple and is surprisingly good but very hard to calibrate . I guess this was one of the reasons why they were eventually superseded by the Capacitor/Inductance tuned circuit that can be directly calibrated.

I have always been amazed how well these simple crystal radios actually work. Its seem as long as you keep to good radio practice by using the best materials ie Paxolin for the coil former and good quality wire with tight windings of at least 4 inches diameter coils they work well, cut any corners and performance drops right off.

This project worked very well and turned out to be a little feat of engineering that had great sculptural artistic qualities as well.

Geoff's Dual Slider Radio Coil Detail
Geoff's Dual Slider Radio Perikon Detector Detail

Geoff's Dual Slider Radio Slider Detail

The Slider

Radio dual slider coil up close

The contact on the coil winding has to be a mechanically positive one ie, a very good electrical connection or noise will be generated when the slider is moved from one end of the coil to the other. On most vintage sets this is just a strip of springy metal usually of a Copper alloy containing Beryllium. This I guess was done for cheapness or fast production and it also wears out the coil wires much quicker and bridges too many wires.

Radio slider parts detail

A smoother and more engineered approach to this is to use a Phosphor Bronze ball in a socket and spring load this with a coil spring. It is so much smoother and noise less.

Mystery Set MK5

Austrialian Mystery Crystal Radio Austrialian Mystery Crystal Radio Austrialian Mystery Crystal Radio

This is a receiver based on the Australian Mystery Crystal Radio design. It has more brass than the original Aussie design. This is the Mk5, S/N 13 design.

Hi Dave (the webmaster) I have decided to call the MK5 set The Sgt Pepper Magical Mystery Crystal Set , after the Beatles Album. Because its a Magical Mystery set that will blow you away. I need taking away too Hahaha.

Geoff's Crystal Sets, Page 1

Geoff's Crystal Sets, Page 3