Crystal Radios a Growing Fasination.

Anyone whose visited my Beltane designs site Beltane Products will see I like to make things from raw materials like leather and wood and brass. Mostly functional things with an artistic theme running throughout the design but there is also the scientific side of me that also is bursting for expression.

Since my early youth I had a training in electronics and radio. My workshop has grown with some basic engineering equipment like lathes engraving machine, drill presses and fly presses many hundreds of hand tools all crying out to be used. It seemed a logical step for me to blend both the scientific and the artistic and come up with a different form of expression.

The crystal radio strange as it might seem has a facination and a satisfaction within my creative ability. Trouble is Ive never really made anything for myself in all these years things go out of my workshop to other people. I guess I really enjoy giving and making for others more than keeping things for myself.

These radios have been sold. I can make a custom made radio for you. Please enquire.

Crystal Radio Earth Station Receiver Mk1

Order Nr. Mk 1 Crystal radio.(sold)

This was the first radio I made using a home made oak box and engraved Gravoply. I wanted to create a simple but classic look. I used a Calrad Type Vernier dial for slow motion tuning but although it worked well I was not exactly happy with the visual appearance being too modern.

The coil on this set was wound with an AVO Douglas coil winding machine that I renovated. The old AVO's machine was completely worn out when i got it and I had to get a new traverse thread made before it would wind anything resembling a coil. I now wind all my coils from .15mm up to .5 mm wire on this machine for heavier coils I use a modified Lathe.

(See AVO Photo).

The Mk1 set wilst looking ok was prone to the old problem with simple single coil sets of overloading and damped tuning range, it was an interesting experiment though which has lead the way to other projects of a more advanced design.

Crystal Radio Earth Station Receiver Mk2

Order Nr. Mk 2 Crystal Radio (Sold)

I wanted to extend the limited tuning range of the Mk 1 radio and I added a tapped coil to this radio. I could switch the main inductance from 100- 400 microhenries. I also put on an aerial coupling coil which helped reduce the overloading and damping.

I have wound all the coils I have made so far on 'Paxolin' which is a trade name for a form of Bakelite. It is still one of best insulating material for coils because it is 'Dry' electrically it looks and smells great remember that old radio from the 20's and 30's this was the material that gave it that characteristic smell. It is very hard to find this material today as its not made anymore in large quantities. I was very lucky to find quite a few feet of it from a de- commissioned transmitting station it is Genuine Vintage Tube.

Mk3

Order Nr. Mk3 Mystery Crystal Radio.(Made for Thomas Fussing)

This set was my first to use all brass fittings. I prefer to use solid brass rather than nickel plate it seems to enhance the look of quality and I can make many of the parts on the lathe to match up all the fittings. I made a plug in coil for medium wave band and I can simply plug in a Longwave or Shortwave coils on this set. I did not want to restrict what type of coil design I used ultemately so I can swap over to spider or basket weave coils later to make comparisons with performance.

I made the box from solid oak and finished it with 'Rustins Teak Oil'.I liked the look of the natural oak its grain showed up much better than staining the usual dark brown colour of vintage oak boxes. I always enjoy listening on these projects when theyre finished it gives me a sence of satisfaction hearing as well as seeing the end results.

This set has a Bogen type T725 Transformer to change the output impedance from High to low to match whatever phones I have around the workshop and to also see how they compare for sound level and quality.

Crystal Radio Mystery Receiver Mk4

Order Nr. Mystery Receiver Mk4

Mk4 Medium Wave 'Mystery Coil' Radio with Built in Antena Tuner and Output Matching Transformer. All Engraved Legends and Mitred Solid Oak Base.

Works Great and is selective.Was A nice project

Jules Verne

Order Nr. Jules Verne

I have desided to call this the Jules Verne set. Did you ever see the film '20000 Leagues Under the Sea'? This reminds me in some way like the inside of Captain Nimos Nautilus submarine with all its brass dials. There is enough Naval brass on this set to sink a Battleship!!

This set has Aerial tuner built in plus adjustable impedance output for any phones from 8 ohms to 5 K ohms.

The Aerial tuner coil can slide along the twin brass rail to get a closer coupling to the main tuning coil . I used a Berilium Copper spring to make contact with the rails and it worked out well with smooth travel. I have based this design on Dave Schmarder's #70 set.

Loose Coupler For Long and Medium Wave.

Order Nr. Loosecoupler MK-1

This is a dual slider main coil plus retractable detector winding. The detector winding is switchable. The main winding has slideable and stepped positions so you can return to a specific point on the coil.

The main coil is 4 inches diameter and 7 inches long the retractable coil is 3 inches diameter and 6 inches long. The overall set is 13 inches long. I wound the large coil on a modified woodworking lathe and the smaller coil was wound on my AVO machine.

The retractable coil slides along twin brass rails and is very smooth and makes good contact.The spring loaded switch makes a very good contact on the switch studs. There is an internal spring which pulls the contacts together.There are six tappings on the coils. I based the design on a 1920's Murdock set from USA.

It was a satisfying craft project but for the amount of work (50 hours). It looks better than it actually works. This particular type of set was dropped by manufacturers in the 1920's for exactly the same reasons. Other simpler sets work possibly better but from a visual point of view these sets are stunning and highly collectable items.

Please click on the photographs for a larger picture of this beautiful wireless receiver.

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© 2008, Geoff Roberts. All Rights Reserved